Determination of a new antibronchospastic agent, MX2/120, in guinea pig plasma by high-performance liquid chromatography in a pharmacokinetic study.

7-[(2,2-Dimethyl)propyl)]-1-methylxanthine (I, Lab code MX2/120) is a new potent antibronchospastic agent. A rapid and simple HPLC assay for I in guinea pig plasma has been developed. Compound I was extracted from plasma with dichloromethane by a solid-phase extraction procedure, after adding 1,3-dimethyl-7-pentylxanthine at a concentration of 5 micrograms/ml as the internal standard (I.S.). The extraction residue was redissolved in water-acetonitrile and chromatographed on a RP-18 reversed-phase column. The eluate was monitored by spectrophotometric detection at 280 nm. The method showed good linearity over the range 0.1-20 micrograms/ml (r = 0.9998) and is precise (C.V. x Student's t-test = 1.84%) and accurate (mean recovery +/- limit of confidence = 100.25 +/- 0.34). The HPLC assay was successfully applied to the determination of the pharmacokinetic profile of I after intravenous and oral administration in guinea pigs. The main pharmacokinetic parameters are presented.