Oral and intravenous pharmacokinetics of milrinone in human volunteers.

Thirty-nine healthy men received milrinone either orally or intravenously in two separate double-blind, placebo-controlled studies. The mean bioavailability, based on the area under the plasma concentration versus time curves, was 0.92. The plasma data for those subjects in the intravenous study were described by an open two-compartment model with a mean (+/- SD) apparent first-order terminal elimination rate constant (beta) of 0.86 (+/- 0.23) h-1, which corresponds to a half-life of 0.8 h. In the intravenous study, the renal clearance and total body clearance were 21.1 and 25.9 L/h, respectively. The corresponding values in the oral study were 23.8 and 29.7 L/h. Between 79.9 and 84.5% of the total doses were recovered in the urine samples taken at 0-24 h.

Determination of isoetharine in plasma by reversed-phase chromatography with amperometric detection.

A reversed-phase liquid chromatographic method for the determination of isoetharine in blood plasma, utilizing amperometric detection, is described. Plasma samples were extracted utilizing an ion-pair reagent, di-(2-ethylhexyl)phosphoric acid, to concentrate the catecholamine. Only minor differences were observed in the relative bioavailability of isoetharine hydrochloride and isoetharine mesylate after oral administration to rats. Observed plasma levels, at 1 hr after oral medication, were highly variable in dose-ranging studies at doses of 800-2500 mg/kg/day for 2 weeks.

Cardiovascular effects and blood concentrations of ajmaline and its 17-monochloroacetate ester in cats.

The antiarrhythmic drugs ajmaline and its 17-monochloroacetate ester (MCAA; Rtimos-Elle) were studied in cats. MCAA was less than half as toxic as ajmaline. Non-lethal doses of MCAA decreased blood pressure before heart rate, whereas ajmaline initially decreased heart rate. Both drugs prolonged the PR, QRS and QT intervals of the EKG. Recovery of these effects was within one hr. MCAA (10 mg/kg) and ajmaline (4.05 mg/kg) were studied separately by a one and 10 min infusion in the same cat. The dose of MCAA was ten times the usual dose in man and that of ajmaline four times the usual clinical dose. More marked effects were observed with the one min infusion. Arrhythmias were usually observed with ajmaline, but not with MCAA, even though it was rapidly converted to ajmaline. Maximal cardiovascular effects of MCAA and ajmaline were observed within 3 min of the end of infusion, which was also the time of peak blood levels. The elimination of MCAA resembled the kinetics of a multi-compartment system after a one min infusion. Peak blood levels declined by one-half in 3 min. Ajmaline blood levels declined linearly, with a half-life of 100 min, after a one min infusion. The peak blood level of MCAA after an intraduodenal dose of 25 mg/kg occurred at 20 min, whereas the peak blood level of the ajmaline formed occurred at 4 hr. In conclusion, MCAA has some different pharmacological properties and different kinetics of elimination than ajmaline.

The pharmacokinetics and pharmacodynamics of sulfinalol hydrochloride in dogs after intravenous administration.

The pharmacokinetic behavior of sulfinalol hydrochloride, an antihypertensive agent with vasodilator and beta-adrenergic blocking activity, was determined in dogs after intravenous administration. The plasma concentrations of sulfinalol HCl were fit to an open two-compartment body model. The mean values for the alpha- and beta-phase constants were 33.3 hr-1 and 0.52 hr-1, respectively. The mean plasma clearance was 2.30 L/kg X hr. The steady-state volume of distribution was approximately four times the body weight of the animals. The urine data gave renal clearance rates approximately equal to the normal glomerular filtration rate in the dog. About 7.5% of the administered dose was excreted in the urine as free sulfinalol hydrochloride. The time course of the hypotensive effect of sulfinalol appears to be better correlated with calculated tissue levels of drug than with observed plasma levels.

A gas chromatography-mass fragmentographic method for the assay of ajmaline and its monochloroacetyl ester.

A gas chromatograph-mass fragmentography method for simultaneous assay of 17-monochloroacetyl-ajmaline (MCAA) and its hydrolysis product, ajmaline, is described. Recovery of both compounds from whole blood averaged 71%. About 5% of MCAA was hydrolyzed during the assay procedure. The method was accurate and precise to within a few percent. It was suitable for assays of blood levels in the dog after an i.v. dose of 2 mg/kg or an oral dose of 5 mg/kg.