Flip-Flop Kinetics

A pharmacokinetic scenario in which the rate of drug absorption is slower than the rate of elimination, causing the terminal slope of the plasma concentration-time curve to reflect the absorption rate rather than the elimination rate. This reversal of the usual relationship makes the apparent terminal half-life dependent on formulation rather than intrinsic clearance.

Beispiele

• Depot intramuscular injections of penicillin G benzathine (absorption-limited for weeks)
• Sustained-release oral formulations of nifedipine
• Transdermal fentanyl patches where skin depot controls apparent half-life