CHAPTER FIVE

Pharmacology

GENERAL CONCEPTS OF site of action. Use the acronym ADME to remember

PHARMACOLOGY these processes.
No medication has a single action; all medications have 1. Absorption: movement of the drug from site of
the potential to alter more than one body function. administration to the blood.
a. Drug action may be increased or decreased by
altering gastric emptying time, changing gastric
  NURSING PRIORITY  Many medications have several pH, or forming drug complexes.
desirable actions. Carefully evaluate the question as to what the
b. Method of administration affects absorption: for
desired response of the medication is for the specific client
situation. Example: Aspirin is used to prevent platelet aggregation
example, IV versus oral.
to prevent strokes and cardiac disease, but it is also used as an 2. Distribution: movement of the drug throughout the
antipyretic and for pain control in arthritis. body.
a. Based on blood flow of drug to tissue, ability of
the drug to leave the vascular system, and ability
A. Drug names: Drug Amendments of 1962 made it man- of the drug to enter the tissue cells.
datory that each medication have one official name. b. Albumin (protein) always remains in the blood-
1. Generic name (nonproprietary): the official desig- stream; drugs that are protein-bound restrict the
nated name under which the medication is listed in drug distribution.
official publications (e.g., acetaminophen). 3. Metabolism: the enzymatic alteration of the drug
2. Chemical name: designates the specific chemical structure; most drug metabolism occurs in the
composition of the medication; usually quite long liver.
and complicated to pronounce and spell (e.g., a. The most important action of drug metabolism is
N-acetyl-para-aminophenol). promotion of the renal excretion of the drug.
3. Trade name (proprietary, brand name): the name des- b. Converts drugs to inactive compounds; also
ignated and registered by a specific manufacturer increases or decreases toxicity.
(e.g., Tylenol). 4. Excretion: the removal of drugs from the body.
a. Kidney is the most important organ for excretion
  NURSING PRIORITY  Typically, the medications on the of a drug; in renal failure, the duration and the
NCLEX-RN examination will be identified with both the generic intensity of drug action may increase.
and trade name—for example: diazepam (Valium). b. Kidney of a newborn is not fully developed; infants
have a limited ability to excrete drugs.
B. Abuse potential: Controlled Substances Act, 1970, c. Drugs are also excreted in breast milk, bile and the
defines rules for the manufacture and distribution of lungs.
drugs that are considered to have a potential for abuse.
1. Defines drugs in five categories: Schedules I, II, III,
IV, V—potential for abuse becomes lower with each   OLDER ADULT PRIORITY  Creatinine clearance should be
monitored to evaluate renal function, not serum creatinine levels.
subsequent category; thus the higher the schedule
The source of serum creatinine (lean muscle mass) decreases
number, the lower the potential for abuse.
with the decline in renal function, which may reveal normal
2. Schedule I drugs are highly addictive (e.g., heroin) serum creatinine levels even though renal function is decreased.
and are not used for medicinal purposes in the U.S.
Schedule V drugs (e.g., diphenoxylate hydrochloride
[Lomotil]) pose the lowest risk for abuse and repre- Drug Actions
sent the lowest level of pharmacokinetics. A. Desired action: the desired, predictable response for
C. Pharmacokinetic process: consists of four phases, acting which the medication is administered.
together to determine the concentration of a drug at its B. Adverse drug reactions (ADR).
81
82 CHAPTER 5  Pharmacology

E. Dependence: an expected response to repeated use of a

  OLDER ADULT PRIORITY  ADRs are 7 times more common
drug, resulting in physical signs and symptoms of with-
in older adults than in young adults.
drawal when the serum drug level decreases suddenly.
For example, when a client abruptly stops taking a strong
1. Side effects: undesirable drug effects, ranging from opioid agonist (methadone) and develops irritability,
mild untoward effects to severe responses that occur nausea, vomiting, muscle spasm, and musculoskeletal
at normal drug dosages. pain.
2. Toxicity: drug reactions that primarily occur as a F. Addiction: the continued use of a psychoactive substance
result of receiving an excessive dose (e.g., medication regardless of physical, psychologic, or social harm.
error, poisoning). However, this may also include
severe reactions (anaphylaxis) that occur regardless of Drug Interactions
the dose. A. Potentiation effect (synergistic effect): if two or more
3. Allergic reactions: drug reaction that occurs as a result drugs are given together and this increases the therapeu-
of prior sensitization and results in an immune tic effects, it is beneficial; if it increases adverse effects,
response. Intensity can range from very mild to very it may be detrimental.
severe. Example: A desirable potentiation effect occurs when a
4. Idiosyncratic effect: an uncommon drug response. diuretic and a beta blocker are given for hypertension. An
undesirable effect can occur when warfarin and aspirin (both
ALERT  Assess client for actual or potential side effects and anticoagulants) are given together, because this increases the
adverse effects of medications; identify symptoms/evidence of risk for spontaneous bleeding.
allergic reactions to medications; implement procedures to B. Antagonistic or inhibitory effect: if two or more drugs
counteract adverse effects of medications; evaluate and are given together, one may inhibit the effect of the
document client response to actions taken to counteract side other; this may be beneficial or detrimental.
effects and adverse effects of medications. Example: When you administer an adrenergic beta blocker
propranolol (Inderal) with an adrenergic beta stimulant iso-
C. Factors influencing dose-response relationships. proterenol (Isuprel), the action of each drug is canceled.
1. Age: young infants and the older adult client are However, the use of naloxone (Narcan) to suppress the effects
generally more sensitive to medications. of morphine results in a desirable inhibitory effect.
2. Medication history: a new medication may produce C. Unique response effect: this occurs when two drugs are
an interaction with one of the medications the client given together and the effect creates a new response not
is currently taking. seen when each drug is used alone.
3. Drug half-life: the time required for the amount of Example: When you administer disulfiram (Antabuse) and
the drug in the body to be decreased by 50%. the client has ingested alcohol or is using products containing
a. Some drugs have short half-lives; they leave the alcohol, the effects are undesirable.
body quickly. Drugs with long half-lives leave the D. Drug incompatibility: a chemical or physical reaction
body more slowly. For example, morphine has a that occurs when two or more drugs are combined in
very short half-life (approximately 3 hours), vitro (outside the body).
whereas levothyroxine (Synthroid) has a half-life 1. Do not combine two or more drugs in the same
of 7 days. container unless it has been established that an inter-
b. The half-life of the drug will determine the dosing action will not occur.
intervals. 2. When intravenous (IV) drugs are combined, they
4. Presence of disease process, specifically kidney and may form a precipitate. Do not give an IV solution
liver problems. in which a precipitate has formed after mixing
5. Method of administration. drugs.
6. Adequate cardiac output.
7. Emotional factors: clients are more likely to respond
to a medication in a positive manner if they have ALERT  Use critical thinking skills when considering the effects
and/or outcomes of medications; identify any contraindications to
confidence in the physician and anticipate therapeutic
administration of a prescribed or OTC medication.
effects.
8. Pregnancy: always ask a woman of childbearing age
if she is pregnant. E. Drug-food interactions.
9. Breastfeeding: advise women who are lactating to 1. Food can bind with drugs and delay drug absorption.
always advise their health care provider; medications Example: Tetracyclines bind with dairy products, leading
may be excreted in breast milk. to a decrease in the plasma tetracycline level.
D. Tolerance: increased dose required to maintain expected 2. Food increases the absorption of nitrofurantoin
drug response. For example, when a client with chronic (Macrodantin), an antiinfective; metoprolol (Lopres-
pain requires higher doses of a strong opioid agonist sor), a beta blocker; and lovastatin (Mevacor), an
(morphine sulfate) to achieve pain relief. antilipemic.
 CHAPTER 5  Pharmacology 83

Example: Grapefruit juice can raise drug levels of calcium d. Emphasize to clients the importance of disposing
channel blockers because it decreases metabolism of the of medications they are no longer taking.
drug by inhibiting an intestinal isoenzyme, CYP3A4, 2. Promoting compliance: intentional underdosing (by
which is needed for drug metabolism in the intestines. clients) is the most common reason for nonadherence
3. Monoamine oxidase inhibitors (e.g., Marplan): anti- to drug regimen.
depressants, which when taken with tyramine-rich a. Provide written instructions to clients regarding
foods (e.g., cheese, wine, organ meats, beer, yogurt), medication administration, as well as why they are
may lead to a hypertensive crisis. taking the medication.
F. Drug-laboratory value interactions. b. Ask the pharmacist to label drug containers with
1. Abnormal plasma or serum electrolyte levels can large type.
affect drugs. c. Provide drug containers that can be opened
Example: Digitalis toxicity can occur when a client’s easily.
serum potassium and magnesium levels are decreased and d. Encourage clients to use a system to record or
the serum calcium level is increased. track their drug doses (calendar, pill organizer).
e. Determine whether clients can afford their
medications.
  NURSING PRIORITY  The peak drug level is the highest C. Food and Drug Administration pregnancy risk catego-
plasma concentration of a drug at a specific time. The trough ries (Table 5-3).
level is the lowest plasma concentrations of a drug and measures
the rate at which the drug is eliminated. Trough levels are Herbal Supplements
determined a few minutes before the drug is to be given,
regardless of whether it is administered orally or intravenously.
A. Herbal medicine can be defined as the use of plant-
These levels are determined for drugs that have a narrow derived products to promote health and relieve symp-
therapeutic index and are considered toxic (e.g., aminoglycosides toms of disease.
and other antibiotics). B. Herbal medicine is the most common form of alternative
medicine, which can be defined as treatment practices
that are not widely accepted or practiced by mainstream
Drug Therapy Considerations Across clinicians in a given culture.
the Life Span C. The word natural is not synonymous with safe! Remem-
A. Pediatric implications (Table 5-1). ber, poison ivy and tobacco are natural too.
B. Older adult implications (Table 5-2). D. Some commonly used medicinal herbs (Table 5-4).
1. Avoiding adverse drug reactions.
a. Obtain a complete drug history that includes
over-the-counter drugs and herbs.   NURSING PRIORITY  Unlike conventional drugs, herbal and
b. Monitor client responses and drug levels. other dietary supplements can be marketed without any proof
c. Keep dosing regime as simple as possible, use daily of safety or efficacy. Dietary supplements are not regulated by
dosing when possible rather than twice a day. the FDA.

Table 5-1 PEDIATRIC PHARMACOLOGY AND NURSING IMPLICATIONS

Pharmacokinetics Body Effects and Possible Drug Responses

Absorption Gastric emptying time is prolonged and irregular until about 6 months; delayed gastric emptying enhances
drug absorption.
Drugs administered IM to newborns may be poorly absorbed; by early infancy drugs are absorbed more rapidly.
Topical drugs may be absorbed more quickly than in adults because infants have a proportionally greater body
surface area; infant’s skin is thin and drugs pass through more readily.
Distribution Phase Protein-binding capacity does not reach adult values for 10-12 months; dosages for protein bound medications
may need to be reduced in infants.
Blood-brain barrier is not fully developed in infants; therefore it is easier for drugs and chemicals to enter the
CNS.
Infants and children have lower blood pressure.
The liver and brain are proportionally larger and receive more blood flow.
Metabolism Drug metabolizing is decreased in the infant due to an immature liver. Liver does not develop to full capacity
until about 1 year.
Excretion Blood flow volume through the kidneys is less than in adults, and glomerular filtration rate is significantly
lower.
At birth there is a significant decrease in drug excretion by the kidney.
Adult level of renal excretion occurs around 1 year.
84 CHAPTER 5  Pharmacology

Table 5-2 OLDER ADULT PHARMACOLOGY AND NURSING IMPLICATIONS

Pharmacokinetics Body Effects and Possible Drug Responses

Absorption Slowed due to decreased gastric motility and blood flow; drug responses may be delayed;
absorption is slowed but not decreased.
Decreased peristalsis with delayed intestinal emptying time.
Gastric acidity is reduced and may alter the absorption of some drugs.
Distribution Decreased serum protein and albumin. Drugs with a high affinity for protein compete for
protein-binding sites with other drugs. Drug interactions result due to a lack of protein sites
and an increase in free drugs intensifying drug effects.
Metabolism Decreased hepatic blood flow, enzyme function, and total liver function results in reduction in
drug metabolism.
With a reduction in metabolic rate, the half-life of drugs increases and drug accumulation can
result. Drug toxicity may occur when the half-life is prolonged.
Excretion Decrease in renal function, therefore a decrease in drug excretion, and drug accumulation results.
Continual assessment for drug toxicity while the client is taking the drug.

  NURSING PRIORITY  Adverse drug reactions secondary to

a decrease in renal function is the primary cause of adverse drug
reactions in the older client.

Table 5-3 FOOD AND DRUG ADMINISTRATION

MEDICATION ADMINISTRATION
PREGNANCY RISK CATEGORIES
  NURSING PRIORITY  The nurse’s responsibility in
Category Description
administering medication is influenced by three primary factors:
A Remote Risk of Fetal Harm: Adequate and nursing guidelines for safe medication administration,
well-controlled studies in pregnant women pharmacologic implications of the medication, and the legal
have not shown an increased risk of fetal aspects of medication administration.
abnormalities.
B Slightly More Risk Than A: Animal studies have
revealed no evidence of harm to the fetus;
however, there are no adequate and Nursing Responsibilities
well-controlled studies in pregnant women. in Medication Administration
or A. Follow the “6 Rights” of medication administration.
Animal studies have shown an adverse effect,
1. Right medication.
but adequate and well-controlled studies in
pregnant women have failed to demonstrate
2. Right dosage.
a risk to the fetus. 3. Right route of administration.
C Greater Risk Than B: Animal studies have 4. Right time.
shown an adverse effect, and there are no 5. Right client.
adequate and well-controlled studies in 6. Right charting (documentation).
pregnant women. No animal studies have
been conducted, and there are no adequate
and well-controlled studies in pregnant ALERT  Administer medications according to the “6 Rights” of
women. medication administration. Refer to Chapter 4 for responsibilities
D Proven Risk of Fetal Harm: Studies—adequate and legal implications.
well-controlled or observational—in
pregnant women have demonstrated a risk
to the fetus. However, the benefits of
B. A nurse should administer only those medications that
therapy may outweigh the potential risk. he or she has prepared.
X Proven Risk of Fetal Harm: Studies—adequate C. Be familiar with medication.
well-controlled or observational—in animals 1. General purpose for which the client is receiving the
or pregnant women have demonstrated medication.
positive evidence of fetal abnormalities. The 2. Common side effects.
use of the product is contraindicated in 3. Average dose or range of safe dosage.
women who are or may become pregnant. 4. Any specific safety precautions that apply before
administration (e.g., digitalis: check apical pulse;
Modified from Lehne RA: Pharmacology for nursing care, ed 7, St. Louis,
heparin: check clotting times).
2010, Saunders; and Meadows M: Pregnancy and drug dilemma, FDA
Consumer Magazine, May-June 2001. Available at www.fda.gov/fdac/ D. Check the medication against the health care provider’s
features/2001/301_preg.html. orders and document according to policy.
 CHAPTER 5  Pharmacology 85

Table 5-4 COMMONLY USED MEDICINAL HERBS

Medicinal Herb Drug Interactions

• Aloe is used for topical skin ailments with little or no topical side None noted with topical therapy.
effects. Oral aloe is used for constipation and can cause severe diarrhea.
Fresh aloe is more effective than stored product.
• Black cohosh is a popular treatment for acute symptoms of menopause May potentiate hypotensive effects of antihypertensive
and premenstrual syndrome (PMS). Minor side effect of upset stomach drugs, as well as hypoglycemic action of insulin
may occur. and oral hypoglycemics.
• Echinacea is used orally to stimulate the immune functions and suppress May oppose effects of immunosuppressant drugs.
inflammation. Side effects include unpleasant taste, fever, nausea, and
vomiting.
• Feverfew for treatment of migraine, fever; stimulates menstruation and May suppress platelet aggregation and increase risk
suppresses inflammation. for bleeding in clients on anticoagulant
medications (aspirin, warfarin, heparin).
• Garlic reduces levels of triglycerides and cholesterol and decreases Increases risk for bleeding in clients taking antiplatelet
formation of atherosclerotic plaque. drugs (aspirin) or anticoagulants (warfarin,
heparin).
• Ginger root used for nausea and vomiting caused by motion sickness Increases risk for bleeding in clients taking antiplatelet
and perhaps nausea caused by chemotherapy. drugs (aspirin) or anticoagulants (warfarin,
heparin).
• Ginkgo biloba is used for increased circulation, memory, clear thinking, Increases risk for bleeding in clients taking antiplatelet
and impotence. May cause stomach upset and dose-related headache. drugs (aspirin) or anticoagulants (warfarin,
heparin).
• Goldenseal is used for bacterial, fungal, and protozoal infections of Contraindicated in pregnancy.
mucous membranes in the respiratory, gastrointestinal, and genitourinary
tracts. Also used to treat inflammation of the gallbladder. Well tolerated
but toxic in high doses.
• Kava is used to relieve anxiety, promote sleep, and relax muscles. Intensifies the effects of CNS depressants.
Long-term use and high doses cause CNS depression, skin problems, Should not be taken with alcohol.
and liver damage.
• Ma huang (ephedra) reduces appetite, increases energy, and relieves Potentiates the effects of CNS stimulants; can
bronchospasms. Increases blood pressure and heart rate. Potentially counteract the effects of antihypertensive drugs.
dangerous to the cardiovascular system with long-term use or in high May cause hypertensive crisis if taken with MAO
doses. inhibitors.
• St. John’s wort is used for depression. Potential interactions with other May interfere with oral contraceptives; reduced
drugs. anticoagulation in clients taking warfarin;
decreased effectiveness of cyclosporine. Caution in
use with antidepressants.
• Saw palmetto is used to relieve urinary symptoms related to benign Avoid use in pregnancy. Should not use with
prostatic hypertrophy (BPH) and is well tolerated. May cause a false- finasteride (Proscar) in treatment of BPH.
negative result on PSA test.
• Valerian is a sedative to promote sleep and reduce restlessness. One
possible side effect is daytime drowsiness. With high doses and long-
term use, headache, nervousness, or cardiac abnormalities can occur.

E. Evaluate client’s overall condition and assess for changes ALERT  Evaluate appropriateness/accuracy of medication order;
that may indicate the medication is contraindicated (e.g., review pertinent data before medication administration; identify
morphine would be contraindicated in a client who has potential and actual incompatibilities of prescribed client
increased intracranial pressure). medications.
F. Evaluate compatibility with other medications the client
is receiving.
G. Use appropriate aseptic technique in preparing and Nurse’s Legal Responsibilities in
administering medication. Administration of Medication
H. Do not leave medications at the client’s bedside without A. The nurse administers a medication only by order of a
a doctor’s order to do so. physician or health care provider and according to provi-
I. If client is to administer his or her own medication, sions of the specific institution.
review the correct method of administration (e.g., eye B. The nurse should not automatically carry out an order
drops) with the client. if the dosage is outside the normal range or if the route
 86 CHAPTER 5  Pharmacology

of administration is not appropriate; he or she should

Box 5-1  NURSING IMPLICATIONS FOR HIGH-
consult the physician. ▲ ALERT MEDICATIONS
C. The nurse is legally responsible for the medication he or
she administers, even when the medication is adminis-
•  Maintain good communication and locate easily found
tered according to a physician’s order.
information regarding the administration of pain medica-
D. The nurse is responsible for evaluating the client before
tions to prevent overdose. You may use a visual pain scale.
and after the administration of an as-needed (PRN) Limit the number of opiates and narcotics that are housed
medication. as floor stock. Store narcotics in individual client areas rather
E. The medication should be charted as soon as possible than as floor stock.
after administration. •  Do not store together medications that have the same type
F. When taking oral orders on the phone, the nurse should of measurements. For example, heparin and insulin are both
carefully repeat all the orders to verify they are correct administered in units.
(see Chapter 4, Box 4-3 for additional tips). •  Use only accepted abbreviations (see Appendixes 5-2, 5-3,
G. Medication errors. 5-4).
1. If an error is found in a drug order, it is the nurse’s •  Establish a check system where one nurse prepares the medi-
cation and another nurse reviews it.
responsibility to question the order.
•  Infusion pump rates and concentrations must have an inde-
2. Always report medication errors to the appropriate pendent check system.
health care provider immediately. •  Identify and exercise caution with medications that have
3. It is the nurse’s responsibility to carefully assess the similar names. For example, hydromorphone (Dilaudid) and
client for effects of the erroneous medication. morphine; potassium phosphate and potassium chloride;
4. Medication errors should be documented in an inci- methyldopa (Aldomet) with levodopa or L-dopa.
dent report and on the client’s chart. •  Increase the use of standardized concentrations and pre-
5. The U.S. Pharmacopeia and the Institute for Safe mixed solutions (potassium chloride, sodium chloride or
Medical Practices (ISMP) have developed a nation- normal saline) on the nursing unit; decrease the premixing
wide medication errors reporting program called and calculation of medications on the nursing unit.
Medication Errors Reporting (MER) Program. Report- •  Do not store vials or containers of saline in concentrations
above 0.9% on the nursing unit.
ing is confidential and can be done via Internet,
•  Use single-dose vials when possible.
phone, or fax.

ALERT  Identify situations in which the reporting of an incident/

event/irregular occurrence/variance is appropriate; report the ALERT  Administer and document medications given by common
incident/error/event/occurrence per protocol. routes (e.g. oral, topical), administer and document medications
given by parenteral routes (intravenous, intramuscular,
subcutaneous), and determine the need for administration of PRN
▲ H. High-Alert Medications. medications.
1. The Joint Commission (TJC) and the Institute for
Safe Medication Practices (ISMP) have identified
specific medications for which errors could have dev- A. Oral medication.
astating effects on clients. 1. Assess level of consciousness and ability to follow
2. These medications are identified within the medica- directions.
tion tables throughout this book. 2. Evaluate swallow reflex.
3. TJC requires: B. Topical medications.
a. Institution or facility to develop processes to 1. Skin application: evaluate condition of the skin in the
manage High-Alert Medications. ▲ area that the medication is to be applied; if appropri-
b. A specific process of communication among ate, rotate sites to prevent irritation.
health care workers to reconcile medications across 2. Sublingual: allow medication to dissolve under the
the continuum of care. This includes a process for tongue; client should not chew or swallow.
reconciling the list of medications during transfer, 3. Nasal: position client to allow nose drops or spray to
at discharge, and after major procedures. enter nares directly without contaminating the eyes.
4. Nursing Implications for High-Alert Medications Position should foster the movement of the medica-
(Box 5-1). ▲ tion to the affected area.
4. Eyes: medication must be specifically indicated for
Methods of Medication Administration ophthalmic use.
Note: This section on medications should not be used as a a. Instill 1 or 2 drops in the middle of the lower
procedure guideline. The purpose is to point out specific conjunctival sac.
characteristics of each method. All medications should be b. Do not allow tip of applicator to come in contact
administered according to previously discussed nursing with the eye.
responsibilities in medication administration. c. Do not drop medication directly on the cornea.
 CHAPTER 5  Pharmacology 87

Intramuscular Subcutaneous Intradermal

90° 90° 45°

15°
Skin

Subcutaneous
tissue
Muscle

FIGURE 5-1  Injection routes. Needle insertion angles for intramuscular, subcutaneous, and intradermal injections.  (From Lilley L, Harrington S, Snyder
J: Pharmacology and the nursing process, ed 5, St. Louis, 2007, Mosby.)

d. Direct client to close his or her eyes gently to

distribute the medication.
e. Make sure you administer the correct medication
in the correct eye.
5. Ears: medication is instilled into the auditory
canal.
a. Position client with affected ear upward.
b. Children under 3 years: pull pinna down and
backward.
c. Older children and adults: pull pinna up and 18 g 22 g 21 g 20 g 22 g 23 g 25 g 25 g
backward. 11/2 in 11/2 in 1 in 1 in 1 in 3/4in 5/8in 11/2 in

d. Administer solution at room temperature.

e. Keep client in the same position for appropriate FIGURE 5-2  Needle gauges and lengths.  (From Lilley L, Harrington S,
time to prevent medication from coming out. Snyder J: Pharmacology and the nursing process, ed 5, St. Louis, 2007,
6. Suppositories. Mosby.)
a. Rectal: absorption of medication from rectal
mucosa is slower and less predictable than that of
medications administered systemically. 1. Place client in semi-Fowler’s position.
(1) Frequently given for constipation or for nausea 2. Check instructions for use of inhaler and make sure
and vomiting. client understands.
(2) May be preferred route for infant. E. Parenteral medications: administration of medications
b. Vaginal: absorption across vaginal mucous by some method of injection.
membranes. 1. Injection routes (Figure 5-1).
(1) Insert suppository about 3 to 4 inches into 2. Selection of a syringe (Figure 5-2): select a syringe
vagina; maintain supine position after and type of needle that is appropriate for the type of
insertion. parenteral medication to be administered.
(2) Should not douche unless advised to do so; 3. Intradermal injection: administered just below the
maintain good perineal hygiene. skin surface.
C. Transdermal medication: medication is stored in a a. Use a syringe with appropriate calibrations because
patch or is measured on a dose-determined applicator amount is very small in volume (0.01 to 0.1 mL).
placed on the skin; absorption occurs through the b. Use a tuberculin or 1-mL syringe with a small-
skin. gauge (25- or 27-gauge) needle, 3 8 to 5 8 inch
1. Provides more consistent blood levels and avoids gas- long.
trointestinal problems. c. Select area where skin is thin (e.g., inner surface
2. Patch sites should be rotated. Old patch should be of forearm, middle of back).
removed and area should be cleansed after use. d. Insert needle bevel edge up at a 5- to 15-degree
3. Patch should not be applied over inflamed areas. angle.
4. Do not allow transdermal medications to come in e. Frequently used for tuberculin testing, administra-
contact with your skin, because medication could be tion of local anesthetic, allergy testing.
absorbed. 4. Subcutaneous injection: medication is injected into
5. Patch must come in contact with skin; excessive body fatty tissue, just below the dermis.
hair may need to be removed. Do not shave the area; a. Medication should be small in volume (0.5 to
use scissors to clip hair from area. 1 mL) and nonirritating.
D. Inhalation medication: medication is in an aerosol or b. Areas on outer surface of upper arm, anterior
powder form and is inhaled and absorbed throughout surface of the thigh, and the abdomen are frequent
the respiratory tract (see Chapter 15). sites.
88 CHAPTER 5  Pharmacology

Acromion
process
Deltoid
muscle
X
Scapula

Deep brachial
artery
Humerus

Radial
nerve

A B
FIGURE 5-3  Deltoid muscle injection site in the upper arm.  (From Potter P, Perry A: Fundamentals of nursing, ed 7, St. Louis, 2008, Mosby.)

Iliac crest

Site of Anterosuperior
A injection iliac spine

B C
FIGURE 5-4  Ventrogluteal intramuscular injection site. Place the palm of your hand over the greater trochanter, with your middle finger pointed toward
the iliac crest, your index finger toward the anterosuperior iliac spine, and your thumb toward the client’s groin. Administer the injection in the center
of the triangle formed by your fingers.  (From Lilley L, Harrington S, Snyder J: Pharmacology and the nursing process, ed 5, St. Louis, 2007, Mosby.)

c. Use a 25-gauge needle that is 5 8 inches long and b. Appropriate sites.

insert at a 45-degree angle; or a 25-gauge needle that (1) Deltoid (Figure 5-3).
is 1 2 inch long and insert at a 90-degree angle. (2) Ventrogluteal (Figure 5-4) and vastus lateralis
5. Intramuscular injection: injection of medication into muscles (Figure 5-5).
1
the muscle. c. Use a 1-inch to 1 2 -inch needle; gauge of needle
a. The amount of medication is usually 0.5 to depends on viscosity of medication; insert needle
3.0 mL. at 90-degree angle.
 CHAPTER 5  Pharmacology 89

Lateral
femoral
Greater Site of
Vastus condyle
trochanter injection
lateralis
of femur
A muscle

B C
FIGURE 5-5  Vastus lateralis intramuscular injection site on the right thigh. Place one hand above the knee and the other hand below the greater
trochanter. Locate the midline of both the anterior thigh and the lateral side of the thigh. Give the injection within the rectangular area.  (From Lilley L,
Harrington S, Snyder J: Pharmacology and the nursing process, ed 5, St. Louis, 2007, Mosby.)

(1) For oil-based or viscous medications use an b. Administration of irritating medications by pig-
18- to 22-gauge needle. gyback method.
(2) For less viscous medications use a 20- to (1) Dilute medication according to directions,
22-gauge needle. usually 25 to 250 mL of a compatible intrave-
d. Aspirate when needle is in place; if no blood nous fluid-like normal saline (NS).
returns, administer medication at a rate of 1 mL (2) Assess patency of primary infusion.
every 10 seconds. (3) Connect medication and adjust flow rate for
e. Z-track technique is used to prevent medication the time designated, usually 30 to 45 minutes.
from leaking back through the needle track and (4) Administration of medications through IV
irritating or staining subcutaneous tissue. piggyback method enhances the action of the
(1) After medication is drawn up, change the medication.
needle. c. Administration of a specific medication into an
(2) Pull skin over to one side at the injection site. already present IV infusion by IV push or bolus
(3) Inject medication into taut skin at site selected. method.
(4) Remove the needle and release the skin. As (1) Clamp tubing of primary IV line, inject the
the stretched skin returns to its original posi- medication slowly, and observe the client’s
tion, the needle track is sealed. response.
(5) The preferable site is the ventrogluteal area. (2) Be aware of the institution’s policy regarding
f. Intramuscular injections in children. guidelines for IV push medications.
(1) Vastus lateralis (see Figure 5-5) muscle is d. Retrograde IV administration: medication is
common site in infants. mixed with diluent, the port closest to client is
(2) Ventrogluteal (see Figure 5-4) site is the pre- clamped and medication is injected into the port
ferred site in children. and allowed to fill (retrograde) into the IV tubing.
(3) A 22-gauge 1-inch needle is appropriate for The clamp closest to the client is opened and the
an IM injection in most children. medication is allowed to infuse at the prescribed
(4) See Calculation of Medication Dosages flow rate.
section for pediatric calculations.
6. IV administration: injection of medication into the Forms of Medication Preparations
blood (Table 5-5). A. Solids.
a. Administration of large volumes of liquid by 1. Capsule: medication is placed in cylindrical gelatin
infusion. container.
90 CHAPTER 5  Pharmacology

Table 5-5 INTRAVENOUS MEDICATION ADMINISTRATION

Method Injection Rate Nursing Implications

Push or bolus Rate of administration is 1. Drug is not diluted and is injected directly into the
determined by the amount of client’s venous system.
medication that can be given 2. Access is most often through an existing IV infusion.
each minute based on each Use the access port closest to the client.
drug’s protocol. 3. Has a rapid effect on the CNS and cardiopulmonary
systems.
4. IV push or bolus is the most dangerous delivery
method. Extreme care should be taken in following the
drug protocol. If in doubt, do not deliver the bolus.
Intermittent infusion or Medication is diluted in 25 to 1. Drug is diluted to decrease toxicity and hypertonicity
piggyback (IVPB) 100 mL and infused over 15 of the solution.
to 60 minutes. 2. Method of choice for multiple daily doses, especially
antibiotics.
3. Concentrated medications require higher dilution and
longer infusion time.
Constant and variable-rate Pump is set to deliver constant 1. Method for medications that need to be highly diluted
infusion rate of infusion based on dose (chemotherapeutic drugs).
of medication and dilution of 2. Provides for continuous medication infusion.
medication.

CNS, Central nervous system; IV intravenous.

2. Pills, tablets: medication is pressed into solid form in the nurse must calculate the correct dosage. Another impor-
various shapes and colors. tant area of calculation is in the administration of IV solu-
a. Enteric-coated: prevents medication from being tions. Thus it is essential that the nurse have a good working
released in stomach; dissolves in intestine. Do not knowledge of the fundamental principles of mathematics to
crush enteric-coated, extended-release (ER), or calculate medication dosages correctly.
sustained-release (SR) tablets.
b. Lozenge: flavored tablet is held in the mouth for Oral Medication Calculations
slow release of medication. Dose desired ÷ Dose on hand = Amount to give
3. Suppositories: generally keep these in cool area; will
melt at body temperature; may produce local or sys- Example: Order reads to give Keflex 500  mg. Dose on hand
temic effects. is 250-mg capsules.
a. Rectal.
b. Vaginal. 500 ÷ 250 = 2 capsules
4. Ointments: used for external application. Dose desired ÷ Dose on hand ×
5. Powders: finely ground medications that are stable Quantity = Amount to give
only in dry form; frequently mixed with solution
before administration. Example: Order reads to give ampicillin 350 mg. Dose on hand
B. Solutions. is 250 mg in 5 mL.
1. Syrups: medication prepared in an aqueous sugar
solution. 350 ÷ 250 × 5 = x
2. Elixirs: solutions containing alcohol, sugar, and water.
350 ÷ 250 = 14
3. Suspensions: finely ground particles of medication
dispersed in a liquid; shake all suspensions well before 14 × 5 mL = 7 mL
preparing dose (antacids).
4. Emulsions: medication is dispersed in an oil or fat The problem can also be set up in algebraic proportion:
solution; shake all emulsions well before preparing
350 x = 250 5 mL
dose.
5. Liniments, lotions: medication dispersed in a mixture 250 x = 1750
of oil, soap, alcohol, water; used for external
application. x = 7 mL

Calculation of Medication Dosages Parenteral Medication Calculations

Occasionally, medications are ordered by the physician in Dose desired ÷ Dose on hand ×
amounts not supplied by the pharmacy. In these situations, Quantity of solution = Amount to give
 CHAPTER 5  Pharmacology 91

Example: Order reads Gentamycin 60  mg IM. On hand is Example: 500 mL is ordered to infuse in 2 hours. Set calibra-
80 mg in 1 mL. tion is 10 gtt/mL.
60 mg ÷ 80 mg × 1 mL = x 500 mL ÷ 120 min = 4.16 × 10 = 41.6 or 42 gtt min
60 ÷ 80 = 0.75 • Determine the number of milliliters per hour and divide
by 60 (60 minutes in 1 hour). This equals the number of
0.75 × 1 mL = 3
4 mL or 0.75 mL
milliliters per minute. Multiply by set calibration of
Set up in algebraic proportion, the equation reads: number of drops per milliliter.
60 mg x = 80 mg 1 mL Number of milliliters per hour ÷ 60 = mL min
60 x = 75 Rate ( mL min ) × Set calibration = gtt min
x = 0.75 mL or 3
4 mL Example: 500 mL is ordered to infuse in 2 hours. Set calibra-
tion is 10 gtt/mL (250 mL/hr to infuse).
Intravenous Medication Calculation 250 mL ÷ 60 = 4.16 mL min
• To determine how long an infusion will run, divide the
4.16 mL × 10 = 41.6 or 42 gtt min
total number of milliliters to infuse by the hourly infusion
rate. Note: There may be a difference of 2 to 4 gtt when different
formulas are used.
Amount to infuse ÷ Hourly rate = Number of hours
Example: Order reads 1000  mL at 125  mL per hour. How Determining Safe Pediatric Dosages
long will it take the 1000 mL to infuse? Calculations for pediatric dosage should be considered as an
1000 ÷ 125 = x approximation of the safe dose range. These calculations can
be used as a guide when evaluating the appropriateness of a
1000 ÷ 125 = 8 hours medication dose order.
• To determine the rate in milliliters per hour at which an Safe dose kg ×
infusion will run, divide the total number of milliliters to child ’ s weight in kg = approximation of safe dose
infuse by the infusion time.
Example: Order reads to give cefaclor (Ceclor) 50  mg qid.
Amount to infuse ÷ Total infusion time = Rate ( mL hr ) The child weighs 9.1 kg. Is this a safe dose?
Safe dose range is 20-40 mg/kg/day in divided doses.
Example: Order reads 1000 mL to run every 8 hours. At what
rate in milliliters per hour will the medication be infused? 20 mg × 9.1 kg = 182 mg
1000 mL ÷ 8 hours = 125 mL hr
40 mg  ×  9.1 kg  =  364 mg/day is the approximate
•  Calculating drop factors: Check the IV equipment to upper limits for maximum safe dose.
determine how many drops are delivered in 1  mL. For The child is receiving 50 mg  ×  4 doses (qid)  =  200 
example purposes, a drop factor of 10 gtt per 1 mL is used. mg/day. This dose is within the approximate safe range
The following are two formulas with which to calculate for a pediatric client.
this factor. The safest formula for evaluating drug dosages in chil-
dren is to calculate the proportional amount of the body
Total mL Time in min = mL per min ×
surface area (BSA) to the body weight. This requires the use
Drop factor = gtt per min
of the West Nomogram (Figure 5-6) for estimation of body
Example: 1000  mL is ordered to infuse in 8 hours. Set drop surface area.
factor is 10 gtt/mL.
1000 mL ÷ 480 min = 2.08 mL min
2.08 × 10 = 20.8 or 21 gtt min
92 CHAPTER 5  Pharmacology

FIGURE 5-6  West Nomogram for Estimation of Body Surface Area. Surface area is indicated where a straight line connecting height and weight
intersects surface area (SA) column or, if patient is approximately of normal proportion, from weight alone (yellow area).  (Nomogram modified from
data of E Boyd by CD West: From Behrman RE, Kliegman RM, Jenson HB, editors: Nelson textbook of pediatrics, ed 17, Philadelphia, 2000,
Saunders).

Appendix 5-1  CONVERSIONS

CELSIUS AND FAHRENHEIT POUNDS AND GRAMS

Fahrenheit reading = 9/5 × Celsius reading + 32 1 pound = 454 grams
To convert pounds to grams, multiply the number of pounds by 454.
Example: Temperature is 50° Celsius
Fahrenheit = 9/5 × 50 + 32 7.5 × 454 = 3405 g
90 + 32 = 122° Fahrenheit To convert grams to pounds, divide the number of grams by 454.
Example: An infant weighs 3405 g
3405/454 = 7.5 lb, or 7 lb 8 oz
 CHAPTER 5  Pharmacology 93

Appendix 5-2  Common ABBREVIATIONS AND SYMBOLS

ac before meals mcg micrograms

ad lib as desired N nitrogen
bid twice daily Na sodium
c with NPO nothing by mouth
Ca calcium OOB out of bed
CBC complete blood count pc after meals
Cl chloride po by mouth
gm gram prn as needed
gtt drops qid four times a day
H2O water q2h every 2 hours
H2O2 hydrogen peroxide q3h every 3 hours
K potassium s without
L liter stat immediately
mL milliliter tab tablet
Mg magnesium tid three times a day

Appendix 5-3  LIST OF “DO NOT USE” ABBREVIATIONS, ACRONYMS, AND SYMBOLS APPROVED BY THE
JOINT COMMISSION (TJC)

ABBREVIATION POTENTIAL PROBLEM PREFERRED TERM

U (unit) Mistaken for “0” (zero), the number “4” (four) or “cc” Write “unit”
IU (International Unit) Mistaken for IV (intravenous) or the number 10 (ten) Write “International Unit”
Q.D., QD, q.d., qd (daily) Mistaken for each other Write “daily”
Q.O.D., QOD, q.o.d, qod (every Period after the Q mistaken for “I” and the “O” Write “every other day”
other day) mistaken for “I”
Trailing zero (X. 0 mg)* Decimal point is missed Write X mg
Lack of leading zero (.X mg) Write 0.X mg
MS Can mean morphine sulfate or magnesium sulfate Write “morphine sulfate”
MSO4 and MgSO4 Confused for one another Write “magnesium sulfate”

From Joint Commission on Accreditation of Healthcare Organizations: The Official “Do Not Use” List Updated—March 2009. Available at www.
jointcommission.org/PatientSafety/DoNotUseList/. Accessed August 5, 2009. © The Joint Commission, 2009. Reprinted with permission.
*Exception: A “trailing zero” may be used only where required to demonstrate the level of precision of the value being reported, such as for laboratory results,
imaging studies that report size of lesions, or catheter/tube sizes. It may not be used in medication orders or other medication-related documentation.

Appendix 5-4  ABBREVIATIONS AND SYMBOLS THAT ARE RECOMMENDED BUT NOT YET MANDATED BY THE
JOINT COMMISSION (TJC) FOR INCLUSION IN THE OFFICIAL “DO NOT USE” LIST

ABBREVIATION POTENTIAL PROBLEM PREFERRED TERM

> (greater than) Misinterpreted as the number “7” (seven) or Write “greater than”
< (less than) the letter “L” Write “less than”
Confused for one another
Abbreviations for drug names Misinterpreted due to similar abbreviations for Write drug names in full
multiple drugs
Apothecary units Unfamiliar to many practitioners Use metric units
Confused with metric units
@ Mistaken for the number “2” (two) Write “at”
cc Mistaken for U (units) when poorly written Write “mL” or “ml” or milliliters”
(“mL” is preferred)
µg Mistaken for mg (milligrams) resulting in one Write “mcg” or “micrograms”
thousand-fold overdose

From Joint Commission on Accreditation of Healthcare Organizations: The Official “Do Not Use” List Updated—March 2009. Available at www.
jointcommission.org/PatientSafety/DoNotUseList/. Accessed August 5, 2009. © The Joint Commission, 2009. Reprinted with permission.
94 CHAPTER 5  Pharmacology

Study Questions  Pharmacology More questions on

companion CD!

  1. The nurse is preparing to administer an intramuscular   7. The nurse is working in the pediatric unit and receives
injection to an infant who is 8 months old. Which a phone order from the doctor for a 10-year-old client
muscle would be the most appropriate injection site? who weighs 40 kg. The order is for ceftibuten (Fortaz)
1 Biceps. 1 g every 8 hours IV. The therapeutic dosage range is
2 Dorsogluteal. 100 to 150  mg/kg/24  hr. What would be the best
3  Vastus lateralis. nursing action?
4 Ventrogluteal. 1 Administer the medication because it is within the
  2. The doctor has indicated that ampicillin and gentami- therapeutic dosage range.
cin are to be given piggyback in the same hour, every 2 Call the doctor to clarify the order since it is outside
6 hours (12-6-12-6). How would the nurse administer the therapeutic dosage range.
these drugs? 3 Call the hospital pharmacist and ask them to calcu-
1 Give both drugs together IV push. late the dosage.
2 Give each drug separately, flushing between drugs. 4 Notify the nursing supervisor and request
3 Retrograde both drugs into the tubing. assistance.
4 Give one drug every 4 hours and one every 6 hours.   8. The nurse is caring for a client who had a stroke (brain
  3. At the shift hand-off report, a nurse is told that one of accident) 3 months ago and is taking Coumadin. The
her clients is becoming tolerant to his pain medication. client tells the nurse she has started taking some herbal
What nursing observation would be in agreement with and vitamin supplements. She gives the nurse a list of
this conclusion? the supplements she is taking. What supplements would
1 The current medication order, which has previously cause concern for the client who is on Coumadin? Select
been effective, is no longer providing adequate pain all that apply:
relief. ______ 1  Garlic.
2 The client becomes irritable and confused before the ______ 2  Cyanocobalamin (vitamin B12).
next scheduled dose of medication. ______ 3  St John’s wort.
3 Pain medication is being administered every 3-4 ______ 4  Vitamin E (alpha tocopherol).
hours around the clock for adequate pain relief. ______ 5  Saw palmetto.
4 The client is sleeping, arouses with physical and ______ 6  Ginkgo biloba.
verbal stimulation, but is very lethargic.   9. The nurse is preparing medications for a client. The
  4. What should the nurse take into consideration when medication order is for cefaclor (Ceclor) 0.1 g PO. The
giving medication to an older adult client? dose available in the unit is 125 mg/5 mL. How many
1 Multiple simultaneous drugs can be dangerous. milliliters will the nurse need to give?
2 The older adult client metabolizes and excretes the Answer: __________ mL
drugs differently than do younger clients. 10. A client is receiving IV antibiotic therapy. The order
3 Medication affects the older adult client during the is for methicillin 750  mg IV. The nurse has a vial on
early hours of the morning. hand that contains 1g. The instructions for reconstitu-
4 Medication has an effect on the respiratory system tion say to add 1.5  mL sterile water. Reconstituted
of the older adult client. solution will contain 500  mg methicillin per milliliter.
  5. What is the first step the nurse should take to How much will the nurse give?
ensure that the right medication is being given to a Answer: __________mL
client? 11. The nurse is verifying whether to give a medication to
1 Check the client’s ID band. a client. What would be the first nursing action?
2 Read the information insert for directions as to 1 Check the client’s name and hospital number.
correct administration. 2 Validate the expiration date of the drug.
3 Check the order with the medication administration 3 Determine the appropriate route of delivery.
sheet. 4 Review the orders on the medication administration
4 Check the expiration date on the medication. record.
  6. The nurse prepares a liquid medication and then finds
that the client no longer needs the medication. What is Answers and rationales to these questions are in the section at
the most appropriate nursing action? the end of the book titled Chapter Study Questions: Answers
1 To keep the count correct, record that the dose was and Rationales.
taken.
2 Charge for the dose because it must be paid for.
3 Record the medication as “not taken” and discard
the poured dose.
4 Pour the medication back into the container.