Drug Administration Routes: Advantages and

Disadvantages as Outlined in Pharmacological Texts

Systemic Routes
Systemic routes aim to deliver the drug into the bloodstream for distribution throughout the body.
This can be achieved via the gastrointestinal tract (enteral) or by other means (parenteral).

Enteral Route

This is the most common and convenient route, where the drug is administered via the
alimentary canal.
1. Oral Route:
The oral route is the most frequently used method of drug administration.
●​ Advantages:
○​ Safest and Most Convenient: It is non-invasive, generally painless, and can be
self-administered.
○​ Economical: Oral dosage forms like tablets and capsules are often cheaper to
manufacture.
○​ No Special Equipment: Does not require sterile precautions or specialized
equipment.
●​ Disadvantages:
○​ Slow Onset of Action: Absorption can be slow and variable, making it unsuitable
for emergencies.
○​ First-Pass Metabolism: Drugs absorbed from the gastrointestinal tract pass
through the liver before reaching systemic circulation. A significant portion of the
drug may be metabolized and inactivated in the liver (first-pass effect), reducing its
bioavailability.
○​ Gastrointestinal Irritation: Some drugs can cause nausea, vomiting, or damage to
the gastric mucosa.
○​ Patient Compliance: Dependent on the patient's ability and willingness to swallow
medication. It is not suitable for unconscious or uncooperative patients.
○​ Interaction with Food and other Drugs: The absorption of many drugs can be
affected by the presence of food or other medications in the stomach.
○​ Unpalatable Drugs: Drugs with an unpleasant taste or odor can be difficult to
administer orally.
2. Sublingual and Buccal Routes:
In this method, the drug is placed under the tongue (sublingual) or between the cheek and gum
(buccal) to dissolve and be absorbed directly into the systemic circulation.
●​ Advantages:
○​ Rapid Onset of Action: Absorption is quick, making it useful for certain
emergencies (e.g., nitroglycerin for angina).
○​ Bypasses First-Pass Metabolism: The drug directly enters the systemic
circulation, avoiding inactivation by the liver.
 ○​ Avoids GI Tract Issues: Can be used in patients with vomiting or when a drug is
destroyed by gastric acid.
●​ Disadvantages:
○​ Inconvenient for Frequent Dosing: The tablet or spray must be held in the mouth
until absorbed.
○​ Limited to Small Doses: Only a small quantity of the drug can be administered.
○​ Unpleasant Taste: The taste of the drug can be a significant deterrent.
○​ Irritation: May cause irritation to the oral mucosa.
3. Rectal Route:
This route involves the administration of drugs in the form of suppositories or enemas into the
rectum.
●​ Advantages:
○​ Useful in Specific Situations: Can be used in unconscious or vomiting patients,
and in children.
○​ Bypasses Hepatic First-Pass Metabolism (Partially): About 50% of the drug
absorbed from the rectum bypasses the liver.
○​ Local Action: Can be used for localized effects on the rectum and colon.
●​ Disadvantages:
○​ Inconvenient and Embarrassing: Can be unpleasant for the patient.
○​ Irregular and Unpredictable Absorption: The absorption can be erratic and
incomplete.
○​ Local Irritation: May cause irritation to the rectal mucosa.

Parenteral Route

This refers to the administration of drugs by injection, bypassing the alimentary canal.
1. Intravenous (IV) Route:
The drug is injected directly into a vein.
●​ Advantages:
○​ 100% Bioavailability: The entire dose of the drug reaches the systemic circulation
immediately.
○​ Rapid Onset of Action: The desired blood concentration and therapeutic effect are
achieved almost instantly, making it the route of choice in emergencies.
○​ Titratable Dosage: The dose can be precisely controlled and adjusted according to
the patient's response.
○​ Suitable for Large Volumes and Irritant Drugs: Large volumes of fluids and
drugs that are too irritant for other routes can be administered, often in a diluted
form.
●​ Disadvantages:
○​ Most Risky Route: Once injected, the drug cannot be recalled. An overdose can
be fatal.
○​ Requires Aseptic Technique: Strict sterile precautions are necessary to avoid
infection.
○​ Painful and Requires Skill: The injection can be painful, and requires a trained
person to administer.
○​ Risk of Thrombophlebitis: Inflammation of the vein can occur due to irritation from
the drug or the needle.
○​ Not Suitable for Oily or Insoluble Preparations: These can cause embolism.
2. Intramuscular (IM) Route:
The drug is injected into a large muscle, such as the deltoid, gluteus, or vastus lateralis.
●​ Advantages:
○​ Reliable and Moderately Rapid Absorption: Absorption is more predictable and
faster than the oral route.
○​ Less Painful than Subcutaneous Injections for Irritant Drugs.
●​ Disadvantages:
○​ Painful: Injections can be painful, and may cause local hematoma.
○​ Variable Absorption: Absorption can be variable depending on the blood flow to
the injection site.
○​ Risk of Nerve Damage: Improper technique can lead to nerve injury (e.g., sciatic
nerve with gluteal injections).
○​ Aseptic Precautions Required.
3. Subcutaneous (SC) Route:
The drug is injected into the loose connective tissue just beneath the skin.
●​ Advantages:
○​ Slow and Sustained Absorption: Provides a slow and steady release of the drug,
suitable for drugs requiring prolonged action (e.g., insulin).
○​ Self-Administration is Possible: Patients can be trained to self-administer certain
medications.
●​ Disadvantages:
○​ Slow Onset of Action: Not suitable for emergencies.
○​ Small Volumes Only: Only small volumes (typically less than 2 mL) can be
injected.
○​ Irritation and Pain: Can be painful and may cause local tissue irritation, which can
lead to abscess formation if proper technique is not followed.
○​ Variable Absorption: Absorption can be affected by factors like blood flow and the
site of injection.

Local Routes
Local routes are used to deliver the drug directly to the site of action, minimizing systemic side
effects.

Topical Route

This involves the application of a drug to the skin or mucous membranes for a localized effect.
●​ Advantages:
○​ High Local Concentration: Achieves a high concentration of the drug at the
desired site.
○​ Minimized Systemic Side Effects: Systemic absorption is generally minimal,
reducing the risk of adverse effects elsewhere in the body.
○​ Convenient and Easy to Use.
●​ Disadvantages:
○​ Messy and Time-Consuming: Application can be inconvenient.
○​ Variable Absorption: Absorption through the skin can be unpredictable and
depends on the condition of the skin.
○​ Local Irritation and Allergic Reactions: The drug or the vehicle may cause local
 skin reactions.

Transdermal Route

This involves the application of a patch containing the drug to the skin for systemic absorption at
a predetermined rate.
●​ Advantages:
○​ Prolonged and Controlled Drug Delivery: Provides a steady and continuous
supply of the drug over an extended period.
○​ Bypasses First-Pass Metabolism.
○​ Improved Patient Compliance: Convenient for drugs that require frequent dosing.
●​ Disadvantages:
○​ Slow Onset of Action.
○​ Skin Irritation: The patch adhesive or the drug can cause local skin irritation.
○​ Limited to Potent, Lipid-Soluble Drugs: Only drugs that are potent and can
penetrate the skin can be delivered by this route.
○​ The patch may fall off unnoticed.

Inhalation Route

Volatile liquids and gases, as well as fine powders and aerosols, are administered via the
respiratory tract.
●​ Advantages:
○​ Rapid Onset of Action: The large surface area and rich blood supply of the lungs
lead to very rapid absorption, almost as fast as the IV route.
○​ Localized Effect on the Lungs: Ideal for treating respiratory conditions like
asthma, as high concentrations can be delivered to the target organ with minimal
systemic side effects.
○​ Dose Can Be Titrated.
●​ Disadvantages:
○​ Specialized Equipment Required: Nebulizers or inhalers are needed.
○​ Patient Cooperation and Proper Technique are Crucial: Incorrect use can lead
to a significant portion of the dose being deposited in the mouth and throat.
○​ Irritation of the Respiratory Tract.
○​ Systemic side effects can still occur if the drug is absorbed into the
bloodstream.