Pharmacodynamics and pharmacokinetics of pinacidil in normotensive volunteers after repeated doses of a new slow-release tablet formulation

Pinacidil (CAS 85371-64-8) is an antihypertensive drug of the class of agents called "potassium channel openers". The pharmacokinetics of were studied after repeated oral administration of a new slow release tablet formulation (Pindac) as compared with the standard slow release capsule formulation in healthy volunteers. Eighteen healthy volunteers (3 males and 15 females), aged from 22 to 48 years, and 49 to 95 kg in weight, were given a 12.5 mg dose of each formulation every 12 h for 7 days on two occasions, in a randomized, cross-over trial with at least two weeks interval between trials. Blood samples were drawn immediately before drug administration on the morning of days 1, 2, 3, 4, 5, 6, and 7 and 0.5, 1, 2, 3, 4, 6, 8, 12, 24 and 36 h after the last drug administration. Blood pressure, heart rate, and respiratory function were assessed at admission and on the morning of day 0 (baseline), 2 and 7, before drug administration, and at 4, 24 and 36 h after the final administration. Pinacidil plasma levels were determined by an HPLC method. Both formulations elicited similar reductions of systolic and diastolic pressures from 4 h after administration, but did not change heart rate. The main model-independent pharmacokinetic parameters of pinacidil (Cmax, Tmax, AUC, MRT), as well as the absorption and elimination half-lives were similar with the two formulations. During the study there were no complaints of side-effects with either of the formulations. One advantage of the new formulation as compared to the capsules is that the tablets can be cut easily and the dosage adapted to a patient's needs.