- Routes of drug administration determine how medicines enter the body, including oral, intravenous, inhalation, and topical methods.
- The route of administration affects the onset, intensity, and duration of drug action.
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Enteral Routes
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Oral (PO):
- Most common, safest, and convenient route.
- Subject to first-pass metabolism in the liver and variable absorption.
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Sublingual/Buccal:
- Absorbed through the oral mucosa (e.g., nitroglycerin). Avoids first-pass metabolism.
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Rectal (PR):
- Partially avoids first-pass effect. Useful when patients cannot take oral medications (unconscious, vomiting).
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Parenteral Routes
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Intravenous (IV):
- Delivers drug directly into the bloodstream.
- Rapid onset, 100 Percent bioavailability, but higher risk of adverse reactions.
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Intramuscular (IM):
- Injected into muscle (e.g., deltoid, gluteus). Absorption depends on blood flow to the muscle.
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Subcutaneous (SC/SQ):
- Injection into subcutaneous tissue (e.g., insulin administration). Slower absorption compared to IM.
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Intradermal (ID):
- Injected into the dermis (e.g., skin testing for allergies, Mantoux test for TB).
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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.
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Inhalational Route:
- Direct delivery to the lungs.
- Rapid onset, useful for anesthetics and bronchodilators.
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Other Specialized Routes:
- Buccal (cheek mucosa)
- Intrathecal (into cerebrospinal fluid)
- Intra-articular (into joints)
- Intraperitoneal, vaginal, etc.
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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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