The elimination of the muscle relaxant drug, carisoprodol, was examine
d in 10 healthy volunteers after an oral dose of 700 mg. In nine subje
cts, carisoprodol was rapidly eliminated, with a mean half-life of 99
+/- 46 min, and extensively converted to meprobamate. Within 2.5 h aft
er carisoprodol intake, meprobamate serum concentrations exceeded thos
e of carisoprodol. Serum levels of meprobamate recorded (15-25 mumol/L
) indicate that meprobamate might contribute to the effect(s) of caris
oprodol. One subject eliminated carisoprodol with an overall half-life
of 376 min, and only small amounts of meprobamate were recorded. This
subject was found to be a poor metabolizer of mephenytoin. In spiked
human sera, protein binding of carisoprodol was in the range of 41-67%
, whereas meprobamate was bound to a lesser extent, 14-24%.