Core30: Pharmacokinetic drug interactions - at the level of elimination

🚰 High-yield / 要点：Elimination-level PK interactions often occur when drugs compete for renal tubular secretion carriers.

Core mechanism / 基本機序

• Some drugs are eliminated by active carrier-mediated tubular secretion.
• If two drugs use the same carrier, they compete.
• Competition can reduce elimination of one drug → plasma level or duration increases.

Classic example / 典型例

• Penicillin + probenecid
  • Penicillin is excreted by active tubular secretion.
  • Probenecid uses the same carrier system.
  • They compete for elimination.
  • Penicillin secretion becomes slower.
  • Penicillin effect lasts longer, so less frequent administration may be needed.

Clinical meaning / 臨床的意義

• This interaction can be intentionally used to prolong drug exposure.
• It can also increase toxicity if the affected drug has a narrow safety margin.

Remember / 覚え方

• Same renal carrier → competition
• Probenecid blocks penicillin secretion
• Slower secretion → longer drug action