BASICS IN PHARMACOLOGY
Sources of Drugs
chemicals
animal
plants
Drug is defined as a substance obtained from mineral, chemical, animal, microbial or plant sources DRUG which is used in the diagnosis, prevention and treatment of disease in humans and animals.
microbial
Dose & Dosage form
Dose is the quantity of drug given at a time so that it results in the desired effect, without causing harm Drug is useful when available in a form in which it is easily handled and given to the patients, e.g. Capsules Tablets
Syrups
Routes Of Drug Administration
Inhalation Oral Sublingual
Topicals
Advantages Advantages Most convenient, most economical Vomiting and diarrhoea and in the patients Safer compared to parenteral unable to swallow administered Drugs that mightSelf irritate the stomach or Disadvantages which are not absorbed orally Irritant, unpalatable Rapid action Advantages Not useful in vomiting Accuracy of dose Site specific action And unconcious patients Disadvantages Decreased systemic adverse effects
Less safe Disadvantages More expensive Local irritation, inconvinience Inconvenient to use, self medication being difficult Liable to cause infection Rectal Injure important structures
Intramuscular
Subcutaneous
Intravenous
PHARMACOLOGYIs the science that deals with the study of drugs.
Pharmacology
PHARMACODYNAMICS DRUG BODY
PHARMACOKINETICS BODY DRUG
DRUG
PHARMACODYNAMICS
DRUG
PHARMACOKINETICS
PHARMACODYNAMICS
RECEPTORS
A Drug Receptor is a specialised target molecule present on the cell surface or intracellularly drug + receptor drug-receptor complex effect
AGONIST
activate the receptors when they occupy it Affinity Good intrinsic activity no activation when they occupy the receptor Affinity No intrinsic activity
ANTAGONIST
DRUG RECEPTOR COMPLEX FORMATION
RECEPTOR
DRUG
DRUG RECEPTOR COMPLEX
Agonist
Antagonist
Drug
Receptor
PHARMACOKINETICS
DRUG ADMINISTERED
ABSORPTION PLASMA
DISTRIBUTION IN THE TISSUES METABOLISM DRUG & METABOLITES IN PLASMA ELIMINATION DRUG & METABOLITES IN URINE, FEACES,BILE
AREA UNDER CURVE
Cmax = Maximum drug concentration Tmax = Time taken to reach Cmax t1/2 = Half life
C max
T max
t1/2
Drug given at this point
Half Life
Measure of the time elapsed for the plasma drug concentration to fall to half its original value (Cmax) Elimination half life from plasma is clinically important for safety profiles of drugs
Sites of Elimination
Renal Faecal Breast milk Pulmonary Saliva & Sweat glands
Additive Effect
1+1=2
When the total pharmacological action of
Two or more drugs administered together Is equivalent to the summation of their individual pharmacological actions e.g. : Ephedrine + Aminophylline treatment
of bronchial asthma
Pharmacology & Pharmacotherapeutics, Satoskar;1997: pg 45
Synergistic Effect
1 + 1= X (>2)
When the total pharmacological action of
two or more drugs administered together is more than the summation of their individual pharmacological actions e.g. :Cotrimoxazole (Sulphamethoxazole + Trimethoprim) Septran
Pharmacology & Pharmacotherapeutics, Satoskar;1997: pg 45
Drug Dosing
OD - Once daily BD - Twice daily TD - Thrice daily QD - Four times daily SOS - During emergency use hs - At bed time Stat - Immediately Bolus - Amount of drug given as IV at a controlled but rapid rate Loading dose - Initial higher dose
ADVERSE DRUG REACTIONS (ADR) (Contd.)
Side effects: occur at normal therapeutic doses & are expected Untoward effects occur at therapeutic doses & are unexpected Toxic effects occur at high doses & /or manifest when the drug is used for a longer duration
Clinical Trials
PHASE OF A CLINICAL TRIAL
Phase I (max. tolerated dose & safety, comprises of small no. of patients) Phase II ( therapeutic effect ) Phase III (comparative study with the current standard therapy, comprises of large no. of patients) Phase IV / Post-marketing Surveillance (PMS) : continuing evaluation that takes place after FDA approval, when drug or treatment procedure is already in the market & available for general use
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