The oral bioavailability of two HMG-CoA reductase inhibitors, pravastatin and lovastatin, was investigated in this randomized, two-way crossover study. Twenty healthy men were randomly assigned to treatment with a 40-mg dose of pravastatin or lovastatin once daily for 1 week; steady state kinetics were assessed after the last dose. After 1 week of washout, each subject received the alternate treatment. Serum specimens were assayed by gas chromatography/mass spectrometry (GC/MS) for intact pravastatin or lovastatin acid and by bioassay for active inhibitor concentration and, after hydrolysis of lactones, for total inhibitor concentration. The systemic bioavailabilities of total (active plus potentially active) inhibitors for the two drugs were different, with the mean AUC value for lovastatin being 50% higher than that of pravastatin (mean +/- SEM AUC0-24 values of 285 +/- 25 and 189 +/- 13 ng-equiv x hr/mL, respectively, P less than .0001). Pravastatin, which is administered as the monosodium salt, is present in the systemic circulation as the open acid; lovastatin, which is administered as the lactone, is present as both open-acid active metabolites (62%) and closed-ring lactone metabolites (38%), which are potentially active. Based on mean AUC values, pravastatin accounted for 75% of the active inhibitors from a pravastatin dose. Lovastatin acid accounted for just 25% of the active inhibitors from a lovastatin dose, with the remainder due to other active metabolites. Significant decreases from baseline in total and low-density lipoprotein (LDL) cholesterol were observed during the first treatment leg for both pravastatin and lovastatin.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacokinetics, pharmacodynamics, and safety of pravastatin, a new selective 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, were evaluated during monotherapy and with subsequent concomitant cholestyramine therapy in 33 patients with primary hypercholesterolemia in this randomized study. After 4 weeks, pravastatin monotherapy (5 mg, 10 mg, and 20 mg twice daily) significantly decreased total cholesterol by 17% to 24% (p less than 0.001 versus baseline) and low-density lipoprotein cholesterol by 23% to 35% (p less than 0.001). High-density lipoprotein cholesterol increased by 8% to 9%, and triglycerides decreased by 6% to 9%. The area under the serum concentration-time curve and maximum serum concentration of pravastatin showed dose-proportionality; time to maximum serum concentration and serum elimination half-life were independent of dose. When added to pravastatin therapy, cholestyramine enhanced the lipid-lowering effects of pravastatin. After 4 weeks of combination therapy, total cholesterol was reduced by 32% to 38% (p less than 0.001 versus baseline), and low-density lipoprotein cholesterol was reduced by 47% to 56% (p less than 0.001). High-density lipoprotein cholesterol increased by 11% to 18% (p less than 0.05). Pravastatin was well tolerated; no clinical adverse events directly attributable to the drug were reported.

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SQ 28,668 is a structural analog of thromboxane A2. It inhibits the effects of thromboxane in vitro. Fifty-six healthy male subjects were given either placebo or three equal daily doses of SQ 28,668 ranging from 25 to 1200 mg. Plasma drug concentrations increased in a dose-dependent manner. The shape of the plasma drug concentration-time curve was consistent with enterohepatic recirculation. The effects of SQ 28,668 on ex vivo platelet aggregation suggested that SQ 28,668 is a specific competitive antagonist of thromboxane A2 with a platelet receptor dissociation constant (estimated by Schild analysis) of about 19 nmol/L. Approximately 94% occupation of thromboxane receptors by SQ 28,668 was required to produce a small but measurable increase of the template bleeding time. Dose-ranging studies of antithrombotic drugs are difficult and expensive. For this reason, a method was developed that allows estimation of the dose of a thromboxane receptor antagonist that would be expected to be therapeutically equivalent to a given dose of aspirin.

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