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. pr imary care.

One hundred seventy-nine patients (age range 27- 84 years) with seated diastolic pressure (SDBP) be- tween 105 and 130 m m H g were recruited. After a 4- week placebo run in period, 157 patients (mean sitting BP 166.4/102.4 m m H g _+ 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 t rea tment 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 m m H g was achieved in 100 (64.9%) patients on low-dose N after 4 weeks of t reatment . 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.

Pat ient 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% [0] [placebo in brackets]. Four patients (2.6%) on low-dose N mono- therapy were withdrawn due to t reatment-related side effects.

L.D. Ritchie 1, L.T. Harrington 2, A.R. MacGregor 3, M.J. V a n d e n b u r g 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.

References

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.

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