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Treatment of hypertension with calcium antagonists and aspirin. Effects on 24-h platelet activity
N Fetkovska1, Z Jakubovska, J Oravcova
1Department of Clinical Pharmacology, Institute of Preventive and Clinical Medicine, Bratislava, Slovak Republic.
Insights
This study shows that calcium antagonists like isradipine and nitrendipine reduce blood pressure in hypertensive patients. Aspirin did not affect blood pressure but altered platelet activity differently with each calcium antagonist.
Area of Science:
- Cardiovascular Pharmacology
- Hypertension Research
- Platelet Physiology
Background:
- Essential hypertension is a common condition associated with cardiovascular risks.
- Platelet activity exhibits circadian variations, potentially influencing cardiovascular events.
- Calcium antagonists are widely used for hypertension management, but their effects on platelet function require further investigation.
Purpose of the Study:
- To investigate the effects of calcium antagonists (nitrendipine, isradipine) on platelet activity in hypertensive patients.
- To determine the impact of aspirin on the antihypertensive efficacy of calcium antagonists.
- To analyze the influence of aspirin on the 24-hour platelet activity profile in patients treated with calcium antagonists.
Main Methods:
- A double-blind study involving patients with essential hypertension.
- Treatment with nitrendipine or isradipine for 8 weeks, followed by the addition of aspirin for another 8 weeks.
- Measurement of plasma beta-thromboglobulin (beta-TG) and platelet aggregation (PA) six times over 24 hours.
Main Results:
- Both isradipine and nitrendipine significantly reduced systolic and diastolic blood pressure; aspirin did not alter blood pressure.
- Platelet activity showed circadian variations, with lowest levels in the early morning.
- Isradipine demonstrated a more pronounced decrease in beta-TG levels compared to nitrendipine; aspirin's effect on beta-TG varied depending on the calcium antagonist used.
Conclusions:
- Hypertensive patients exhibit circadian increases in platelet activity, which can be mitigated by isradipine alone or nitrendipine combined with aspirin.
- Chronic aspirin intake (100 mg daily) does not diminish the antihypertensive effectiveness of calcium antagonists.
Abstract:
The effects of calcium antagonists on platelets, and the effects of aspirin on the antihypertensive efficacy of calcium antagonists and on the 24-h platelet-activity profile were investigated in a double-blind study. Patients with essential hypertension were treated for 8 weeks with either nitrendipine (10 mg once daily) or isradipine (2.5 mg once daily). Aspirin (100 mg once daily) was added to both treatments for a further 8 weeks. Measurements were taken after placebo, after 8 weeks of active treatment, and after 8 weeks of treatment plus aspirin. Plasma levels of beta-thromboglobulin (beta-TG) and platelet aggregation (PA) were measured six times over 24 h. Isradipine and nitrendipine significantly lowered systolic and diastolic blood pressure. The addition of aspirin had no effect on blood pressure. Platelet activity before treatment exhibited circadian variations with the lowest values of beta-TG and PA at 0530 h and the steepest increases between 0530 and 0900 h. Although both calcium antagonists decreased beta-TG levels (P < .05), the effect with isradipine was more pronounced than that with nitrendipine (P < .05). Aspirin added to nitrendipine produced a significant decrease in beta-TG levels whereas isradipine plus aspirin was accompanied by a partial increase in beta-TG. It is concluded that hypertensive patients exhibit circadian increases in platelet activity that can be prevented by either isradipine alone or by treatment with nitrendipine plus aspirin. Chronic aspirin intake at a daily dose of 100 mg does not affect calcium antagonist antihypertensive efficacy.