Enzyme induction following a single dose of amobarbital in dogs.

The elimination of amobarbital in dogs was investigated by injecting various doses of amobarbital into a given animal. At low doses (3 mg/kg) serum levels declined in a first-order fashion. Superficially, at high doses (20 mg/kg) the relationship between serum concentration and time could be quantitatively characterized by simple one-compartment saturable kinetics. Indeed, qualitatively, saturation of the amobarbital-metabolizing enzymes was indicated by a shallower initial slope of the semilogarithmic concentration--time profile at the high than at the low dose. However, in addition, an acute enzyme induction phenomenon was observed which was indicated by a shorter terminal half-life of amobarbital at the high dose than after the low dose and also by a shortening in antipyrine half-life.