Received for publication April 20, 2004.
Revised June 18, 2004.
Accepted for publication June 23, 2004.

EFFECTIVE DOSING REGIMEN OF 1-AMINOBENZOTRIAZOLE FOR INHIBITION OF ANTIPYRINE CLEARANCE IN GUINEA PIGS AND MICE USING SERIAL SAMPLING

Abstract

Single dose pharmacokinetics of 1-aminobenzotriazole (ABT), a potent non-specific inhibitor of cytochromes P450, were characterized after oral administration to mice and guinea pigs at doses of 50, 100 and 150 mg/kg using serial sampling in both species. Only 30 µL blood samples were drawn from jugular vein-cannulated mice using Microvette capillary tubes containing lithium heparin. Comparison of pharmacokinetics of antipyrine (AP) administered IV at 20 mg/kg to mice followed by serial and terminal sampling techniques yielded similar results. The ABT concentrations in plasma were sustained at high levels, 5-100 µM, for at least 12 h in both species. Pretreatment of animals with ABT 2 h prior to AP administration decreased the plasma AP clearance by about 95% in mice at all ABT doses studied, and by 84, 95 and 95% in guinea pigs at 50, 100 and 150 mg/kg ABT dose, respectively. In vitro, the dissociation constants (K_I) for ABT as CYP mechanism-based inactivator were determined to be 45.6 and 193 µM, and the maximal inactivation rate constants (k_inact) were determined to be 0.089 and 0.075 min^-1 for the mouse and guinea pig liver microsomes, respectively. The projected CYP inactivations, at the plasma C_max of ABT, agreed with the inhibitions of CYP mediated AP clearance observed in vivo. For mechanistic studies in vivo overall, a 2 h prior oral pretreatment with ABT at 50 mg/kg in mice, and 100 mg/kg in guinea pigs would provide significant systemic concentrations of the inhibitor over 24 h and inhibition of P450-dependent clearance of test compounds.

Key words: CYP inhibition, inactivation, pharmacokinetics, suicide inhibition