The pharmacokinetics, plasma protein binding and time response relationships of 2-amino-5-phenyl-2-oxazolin-4-one (pemoline) in the horse.

The disposition kinetics of pemoline after iv and oral administration of 2.4 mg/kg of the drug were studied. The elimination half-life was 39.4 hr. The mean volume of distribution was 1.5 liters/kg indicating extensive tissue distribution and sequestration for an amphoteric drug. Plasma protein binding determined by in vitro equilibrium dialysis was concentration dependent. The mean binding capacity was found to be 0.80 mu-mol/g, an apparent dissociation constant of 3.73 X 10(-5) molar, and a total plasma protein concentration of 64.7 g/liter. The mean systemic availability by oral administration was 84.8% with an absorption half-time of 4.9 hr. The time course relationship showed that locomotor activity was directly related to the doses studied.