Routes of Drug Administration

Routes of drug administration determine how medicines enter the body, including oral, intravenous, inhalation, and topical methods.

The routes of administration affects the onset, intensity, and duration of drug action.

1. Enteral Routes

   1. Oral (PO):

      • Most common, safest, and convenient route.
      • Subject to first-pass metabolism in the liver and variable absorption.

   2. Sublingual/Buccal:

      • Absorbed through the oral mucosa (e.g., nitroglycerin). Avoids first-pass metabolism.

   3. Rectal (PR):

      • Partially avoids first-pass effect. Useful when patients cannot take oral medications (unconscious, vomiting).

2. Parenteral Routes

   1. Intravenous (IV):

      • Delivers drug directly into the bloodstream.
      • Rapid onset, 100

   2. Intramuscular (IM):

      • Injected into muscle (e.g., deltoid, gluteus). Absorption depends on blood flow to the muscle.

   3. Subcutaneous (SC/SQ):

      • Injection into subcutaneous tissue (e.g., insulin administration). Slower absorption compared to IM.

   4. Intradermal (ID):

      • Injected into the dermis (e.g., skin testing for allergies, Mantoux test for TB).

3. Topical or Local Routes

   • Cutaneous: Applied to the skin for local effect (creams, ointments).
   • Transdermal Patches: Systemic effect through skin absorption (e.g., nicotine patch).
   • Inhalation: Rapid absorption via the pulmonary route (e.g., bronchodilators, volatile anesthetics).
   • Mucosal Routes: Drops for eye/ear/nasal issues, vaginal administration, etc.

4. Inhalational Route:

   • Direct delivery to the lungs.
   • Rapid onset, useful for anesthetics and bronchodilators.

5. Other Specialized Routes:

   • Buccal (cheek mucosa)
   • Intrathecal (into cerebrospinal fluid)
   • Intra-articular (into joints)
   • Intraperitoneal, vaginal, etc.

Factors influencing route selection:

• Desired speed of action.
• Site of action.
• Patient condition (conscious/unconscious).
• Drug properties (e.g., stability, solubility).

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