The disposition of intravenous doxapram in man

Summary

The pharmacokinetics of intravenous doxapram in healthy individuals is consistent with a three-compartment open model. Doxapram was administered by bolus injection (1.5 mg · kg⁻¹) and by intravenous infusion (6.5 mg · kg⁻¹ for 2 h) to 5 subjects on separate occasions. There was no significant difference in mean terminal plasma half-lives (355 and 448 min) or in mean total body clearances (5.9 and 5.6 ml · min⁻¹ · kg⁻¹) following i. v. bolus injection or infusion respectively. In 3 subjects plasma doxapram concentrations during and after i. v. infusion agreed with those predicted from pharmacokinetic values obtained from the bolus injection study. Since mean steady-state concentrations (9.9 µg · ml⁻¹) would be reached only after an extended interval (mean 15.2 h), a variable-rate infusion regimen was calculated to produce and maintain a concentration of 2 µg · ml⁻¹ from 15–25 min onwards. A regimen in which the infusion rate is reduced step-wise is recommended to achieve early near-constant plasma doxapram concentrations.