Nifedipine as low-dose monotherapy for essential hypertension: A primary care study
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Cardiovascular Drugs and Therapy 3: 341, 1989 Kluwer Academic Publishers. Printed in the U.S.A.
NIFEDIPINE AS LOW-DOSE MONOTHERAPY FOR ESSENTIAL HYPERTENSION: A PRIMARY CARE STUDY
KEY WORDS. nifedipine, hypertension, antihypertensive
Dear Sir Nifedipine has been shown to be an effective and well- tolerated antihypertensive agent, whether used alone [1, 2] or in combination with other therapy [2-4]. Until recently, nifedipine has been available as rapidly ab- sorbed capsules of 5 mg and 10 mg, which are primarily used for angina control, and a slow-release 20-mg tablet (Adalat Retard 20 mg) for hypertension. Vasodilator side-effects (particularly headache and flushing) are occasionally severe enough to warrant withdrawal in the early stages of therapy. As a result of this, a half-strength tablet (Adalat Retard 10 mg) was developed that is galenically similar to the 20-mg formulation.
We assessed the antihypertensive efficacy and tolerability of low-dose nifedipine (N slow release, 10 mg, twice daily) as monotherapy in essential hyperten- sion in a four-center, single-blind study in U.K. primary care.
One hundred seventy-nine patients (age range 27- 84 years) with seated diastolic pressure (SDBP) be- tween 105 and 130 mmHg were recruited. After a 4- week placebo run in period, 157 patients (mean sitting BP 166.4/102.4 mmHg _+ 19.2/7.1 mmHg) were com- menced on N as monotherapy. At the end of 4 weeks, uncontrolled patients (SDBP > 95 mmHg) had their dose increased to 20 mg twice daily.
Reductions in mean SDBP after 4 and 8 weeks of treatment with N were 9.7 and 12.1 mmHg, respective- ly (p < 0.0001). Similar significant falls were registered for seated systolic blood pressure (13.2 and 17.4 mmHg) and for erect systolic and diastolic pressures. Target SDBP of less than 95 mmHg was achieved in 100 (64.9%) patients on low-dose N after 4 weeks of treatment. After a further 4 weeks, 107 (70.3%) had achieved the target pressure. Overall, there was a slight increase in heart rate on active therapy.
Patient tolerability was assessed throughout the study. After 4 weeks of active therapy, overall subjec- tive well-being was little changed. The most frequent side effects reported were headache 9.7% [5.8%]; flush- ing 5.8% [1.9%]; ankle edema 1.9%  [placebo in brackets]. Four patients (2.6%) on low-dose N mono- therapy were withdrawn due to treatment-related side effects.
L.D. Ritchie 1, L.T. Harrington 2, A.R. MacGregor 3, M.J. Vandenburg 4 1Health Centre, Forrest Road, Peterhead, U.K. 2Saint Chad Health Centre, Lichfield, U.K. 3Health Centre, 15 Almswall Road, Kilwinning, U.K. 4MCRC, Romford, Essex, U.K.
We conclude that low-dose, slow-release nifedipine appears to be an effective and acceptable antihyper- tensive and may be the preferred starting formulation in some patients.
1. Bayley S, Dobbs RJ, Robinson BF. Nifedipine in the treat- ment of hypertension: Report of a double-blind controlled trial. Br J Clin Pharmacol 1982;14:509-512.
2. Heagerty AM, Swales J, Baksi A, et al. Nifedipine and atenolol singly and combined for treatment of essential hyper- tension: comparative multicentre study in general practice in the United Kingdom. Br Med J 1988;296:468-472.
3. Murphy MB, Scriven AJI, Dollery CT. Role of nifedipine in treatment of hypertension. Br Med J 1983;287:257-259.
4. Opie LH, Jee L, White D. Antihypertensive effects of nifedipine combined with cardioselective beta-adrenergic receptor antagonism by atenolol. Am Heart J 1982;104:606- 612.
Address for correspondence and reprint requests: Dr. L.D. Ritchie, General Practitioner and Community Medicine Specialist, Health Centre, Forrest Road, Peterhead, U.K. 4B46XP.