Absorption and routes of administration
Explains why route changes speed, peak and risk — the same drug can be gentle or dangerous depending on how it enters.
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- The course lens: biopsychosocial, and no 'chemical imbalance' — Coca leaves vs cocaine vs crack is a route story.
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- First-pass metabolism and prodrugs — Oral routes pass the liver first — first-pass metabolism.
- Half-life and redistribution — Route shapes the rise; half-life shapes the fall.
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What speeds absorption
More surface area, a drug that matches the local pH (its pKa), and higher lipid solubility. Many drugs are slightly basic, so they absorb better in the intestine (pH ≈ 7) than the stomach (pH ≈ 1).
Analogía y ejemplo resuelto
Analogía: Getting into a stadium: IV is being dropped onto the field by helicopter; inhalation is the players' tunnel straight to the pitch; oral is the public entrance with security, queues and bag checks (some fans are turned away); a patch is a slow trickle of fans all game long.
Suboxone is sublingual buprenorphine + naloxone. Why doesn't naloxone block the buprenorphine when taken as prescribed — but does when injected?
- Sublingual bioavailability: buprenorphine ~30%, naloxone <10%.
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Lección completa: Absorption and bioavailability · Oral and rectal administration · Inhaled and mucosal routes · Skin delivery and injection routes