Effect of prazosin GITS, atenolol, nifedipine SR, and enalapril on ADP-induced platelet aggregation.
A randomized, observer-blind, parallel-group study was carried out to compare the effect of prazosin GITS, atenolol, nifedipine SR, and enalapril on platelet aggregation, measured at a time expected to coincide with trough plasma levels of these drugs. 24 patients (age-30 to 60 yrs) with uncomplicated mild to moderate hypertension who completed a placebo run-in phase successfully were recruited in this study. They were randomly allocated to one of the 4 treatments: prazosin GITS 2.5 mg OD (Group 1), atenolol 50 mg OD (Group II), nifedipine SR 20 mg BD (Group III), and enalapril 5 mg OD (Group IV). All the drugs were given for 7 days, and blood samples were collected at 0 hr on day 1 (pre-treatment) and day 8 (post-treatment). Based on the dose (incremental concentrations of ADP)--response (% maximum aggregation) curve obtained, 2.5 microM/L of ADP was used to compare % inhibition of platelet aggregation among the 4 groups. We found that prazosin GITS inhibited % maximum aggregation significantly (p = 0.02) at 2.5 microM/L of ADP. Such inhibitory effect was not seen in any of the other groups. The inhibition produced by prazosin GITS differed significantly from the action of the other 3 drugs (p < 0.05). This antiplatelet effect of prazosin GITS bears more clinical relevance in view of the fact that it was seen at a time which is expected to coincide with the trough plasma levels of prazosin.
Dept. of Pharmacology & Therapeutics, Seth G.S. Medical College, Parel, Mumbai-12.
K C
KC
Patki
S J
SJ
Joglekar
S K
SK
Kamat
U M
UM
Thatte
M E
ME
Yeolekar
N N
NN
Rege
S A
SA
Dahanukar
A S
AS
Nanivadekar
D000244:Adenosine Diphosphate; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology / Q000627:therapeutic use; D000328:Adult; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D000959:Antihypertensive Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001262:Atenolol / Q000494:pharmacology / Q000627:therapeutic use; D002121:Calcium Channel Blockers / Q000494:pharmacology / Q000627:therapeutic use; D003692:Delayed-Action Preparations; D004656:Enalapril / Q000494:pharmacology / Q000627:therapeutic use; D005260:Female; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D009543:Nifedipine / Q000494:pharmacology / Q000627:therapeutic use; D010974:Platelet Aggregation / Q000187:drug effects* / Q000502:physiology; D011224:Prazosin / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D016037:Single-Blind Method
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors; D000959:Antihypertensive Agents; D002121:Calcium Channel Blockers; D003692:Delayed-Action Preparations; D001262:Atenolol; D000244:Adenosine Diphosphate; D004656:Enalapril; D009543:Nifedipine; D011224:Prazosin