Routes of Drug Administration

Study Notes

Drugs can be administered via various routes, each with different advantages and disadvantages.
Understanding these routes is crucial for proper drug administration and patient care.

This route involves administering drugs through the gastrointestinal tract.
Oral administration: Easy, safe, convenient, no need for sterilization, but has delayed onset and variable bioavailability.
Buccal Administration: Local or systemic effect, useful for rapid onset, avoids first-pass metabolism. Examples include lozenges, sublingual nitroglycerin, and transbuccal fentanyl.
Rectal Administration: Less first-pass metabolism, suitable for children, vomiting, and coma patients. Suitable for irritant drugs and drugs destroyed by GIT enzymes. Disadvantages include irregular bioavailability and being disagreeable.
Gastric Gavage: A method of administering medication directly into the stomach using a tube, used in situations where oral intake isn't possible.

This route bypasses the gastrointestinal tract, delivering drugs directly into the bloodstream or other tissues.
Intravenous (IV): Immediate onset, 100% bioavailability; large volumes can be infused; irritant drugs can be diluted; used in emergencies for blood, fluid, or glucose therapy (e.g., thiopental, theophylline). Precautions include using no oily solutions, strict aseptic technique, aspirate blood before injection, exclude air, and slow administration. Disadvantages include the risk of anaphylaxis, extravasation, fat embolism, thrombophlebitis, risk of infection, and the inability to retrieve the dose.
Intramuscular (IM): Rapid absorption, high bioavailability, suitable for depot and oily preparations. Disadvantages include large volumes, accidental IV injections, pain, infection, and abscess formation.
Subcutaneous (SC): Delayed onset, slow absorption, less suitable for large volumes, not suitable for irritant drugs. Disadvantages include lipodystrophy with repeated injections; absorption rate depends on local blood flow and injection site; more painful than IM.
Intradermal: Using a small needle, used for vaccines and hypersensitivity tests.
Other Parenteral Routes: Examples include intracardiac, intraperitoneal, intrapleural, intrathecal, and intra-articular routes.

Drugs delivered through the respiratory system via inhalation or insufflation.
Inhalation: Suitable for pulmonary diseases,e.g., bronchial asthma. Advantages include immediate onset, low systemic adverse effects, and minor first-pass metabolism. However, disadvantages include the need for an intelligent patient, and some drugs may cause irritation/infection.
Insufflation: Similar in application to inhalation.

Delivers drugs through the skin gradually.
Advantages include gradual onset, long duration of action, avoids first pass metabolism, and avoids disadvantages of oral drugs. Disadvantages include local allergy, irregular absorption, and the possibility of the patch falling off. Drugs often delivered via this route include nitroglycerin, nicotine, estradiol, fentanyl, and hyoscine.