Increased cimetidine clearance in burn patients
J. A. Martyn, D. J. Greenblatt and D. R. Abernethy
To determine the etiology of the decreased efficacy of cimetidine in burned
and critically ill surgical patients, we studied the kinetics and dynamics
of the drug in eight burned patients at a mean of 12 days after the burn.
The kinetics were compared with those of nine healthy controls. The
elimination half-life of cimetidine in burned patients was significantly
reduced (2.2 v 1.5 hours), and total clearance significantly increased (8.2
v 13.3 mL/min/kg). Creatinine and total cimetidine clearance were highly
correlated with size of the burn. In the patients studied, 63% of the dose
was excreted in eight hours, compared with 45% after 24 hours in controls.
Gastric pH was maintained at 4 or higher as long as plasma levels of
cimetidine were held above 0.5 microgram/mL. Thus, the increased clearance
of cimetidine might explain the decreased effectiveness of this drug in
burned and possibly other surgical patients. Dose schedules may need to be
altered to compensate for the enhanced clearance of this drug.
