Table 4.

Administration route advantages and disadvantages [55,56,57,58,59,60,61,62,63,64].

Route	Advantages	Disadvantages
Intravenous	Fastest onset of action No bioavailability concerns Bypass first-pass metabolism Large volume can be administered Reliable route for sedated or comatose patients	Highly trained individuals required to administer May require physical restraint Injection site irritation, extravasation, or infection Development of tolerance with continuous infusions
Intramuscular	Bypass first-pass metabolism Prolonged action	Trained individuals required to administer May require physical restraint Painful Variable absorption Injection site irritation or infection Limited volume can be administered (2–5 mL)
Intranasal	Easily administered Rapid absorption Bypass first-pass metabolism Direct drug delivery to blood-brain-barrier	Small volume (≤0.2 mL) hard to measure Short retention time Nasal discharge may alter the absorption Nasal irritation
Buccal and Sublingual	Rapid absorption Bypass first-pass metabolism Low risk of infection	Variable absorption Unpalatable Challenging to place and maintain in the correct location Risk of aspiration
Rectal	Bypass first-pass metabolism Ease of administration in infant emergencies Low risk of infection	Rectal irritation or proctitis with ulceration Less convenient for adults