[The bioavailability of nifedipine in different solid pharmaceutical preparations for oral use]

Abstract

The paper reports on the bioavailability of niphedipine in various pharmaceutic preparations administered in a single dose of 10 mg, per os, to volunteer subjects: Niphedipine dragees (Terapia, Cluj-Napoca), Adalat capsules (Bayer); Adalat coated tablets (Bayer and Birlaşik Alman Ilac Fabricalari, Istanbul) and Corinfar dragées (VEB Arzneimittelwerk, Dresden). In the blood samples collected, niphedipine was determined by a gas-chromatographic procedure. Pharmacokinetic analysis of the experimental data was made by a digital computer. Bioavailability of niphedipine was the best with Adalat capsules. The relative bioavailability of the other products was: tablets (Adalat); 93%; dragées (Niphedipine): 92%; dragées (Corinfar 86%). Absorption speed of Niphedipine decreases in the order: capsules, tablets, indigenous and imported dragées. Statistical analysis (Student test) shows that the differences in bioavailability among the preparations are not important. Efficiently therapeutic plasmatic concentrations are maintained for about 6 hours after a single dose of 10 mg administered as tablets and dragées and for 8 hours in the case of capsules. Important differences exist between the maximum concentration of niphedipine in blood, following some differences in the absorption speed, achieved after administration of capsules, on the one hand, and of tablets and dragées on the other hand. Choosing the type of tablet depends, therefore, on the nature of the affection treated. Niphedipine (Terapia) has corresponding biopharmaceutic properties and is useful in treating hypertension and for preventing and treating anginal attacks.