W. Kielbasa et Hl. Fung, Pharmacokinetics of a model organic nitrite inhalant and its alcohol metabolite in rats, DRUG META D, 28(4), 2000, pp. 386-391
Volatile organic nitrites were originally used to relieve the chest pain th
at is associated with angina pectoris. Today, these inhalants are predomina
ntly used as drugs of abuse. Little is known regarding the bioavailability
and disposition of volatile nitrites. In this study, the pharmacokinetics o
f a major organic nitrite inhalant, isobutyl nitrite (ISBN), and its primar
y metabolite, isobutyl alcohol (ISBA), were investigated after inhalation a
nd i.v. administration. ISBN blood concentrations in the rat declined mono-
exponentially with a half-life of 1.4 min and a blood clearance of 2.9 l/mi
n/kg that vastly exceeded cardiac output (0.3 l/min/kg). Approximately 98%
of ISBN was metabolized to ISBA, which declined monoexponentially with a ha
lf-life of 5.3 min when the infusion of ISBN was terminated. The bioavailab
ility of inhaled ISBN, over a range of 300 to 900 ppm, was estimated to be
43%. After inhaled ISBN, the half-life of ISBA decreased approximately 4-fo
ld (t(1/2) inh = 1.5 min versus t(1/2) i.v. = 5.3 min; P < .001), whereas n
o pharmacokinetic difference was observed for ISBN. Inhalation of another n
itrite, isoamyl nitrite, accelerated the apparent clearance of ISBA, sugges
ting that nitrite inhalation could change the disposition of another compou
nd. A pharmacokinetic model was developed to describe the concentration-tim
e profile of ISBA and ISBN after inhalation and i.v. administration.