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Dihydropyridines Differ In Anti-Hypertensive Effect

Not all long-acting antihypertensives work the same, even when they are from the same drug class.

Investigators from the University of Ottawa, Canada, have found that once-daily formulations of dihydropyridines such as nifedipine and felodipine and angiontensin-converting enzyme inhibitors such as enalapril do not have equivalent effects on daily blood pressure control and left ventricular mass.

Nifedipine-gastrointestinal therapeutic system also provides better sympathetic activation and regression of left ventricular mass than extended release felodipine, report the researchers.

They pointed out that recent meta-analyses had suggest that once-daily dihydropyridines and angiotensin-converting enzyme inhibitors caused similar reductions in left ventricular mass for comparable reductions in blood pressure. But, some dihydropyridines, such as extended release felodipine, still increased sympathetic activity. They might therefore be less effective in reducing left ventricular mass.

The specialists evaluated the effects of long-term (30 weeks) anti-hypertensive treatment with nifedipine-gastrointestinal therapeutic system and extended release felodipine compared with enalapril on left ventricular mass relative to the extent of blood pressure control and sympathetic activity.

Blood pressure control was assessed by 24-hour ambulatory monitoring and sympathetic activity by plasma catecholamine concentrations.

The enalapril was started at 10 mg., the felodipine at 5.0 mg. and the nifedipine at 30 mg., all once daily.

These doses were doubled if office blood pressure remained at 160/90 mmHg or above at the end of the 24-hour dosing interval. Evaluable echocardiograms were obtained for 116 patients when the study ended after 30 weeks of treatment.

On 24-hour ambulatory blood pressure monitoring, nifedipine-gastrointestinal therapeutic system caused a consistent fall in blood pressure throughout the dosing interval.

Extended release felodipine caused a larger fall in blood pressure during the day. Enalapril's effects declined during the night and disappeared by the morning.

Only felodipine significantly increased supine and standing plasma noradrenaline - by more than 50% after 6, 18 and 30 weeks of treatment.

In patients whose systolic blood pressure fell by 10 mmHg or more, enalapril and nifedipine- gastrointestinal therapeutic system caused clear reductions (12-16 gramsm2) in left ventricular mass. Extended release felodipine reduced it by only 6.0 grams/m2.
Canadian Journal of Cardiology 2002;18:12:1285-1293. "Differential effects of once-daily antihypertensive drugs on blood pressure, left ventricle mass and sympathetic activity: Nifedipine-GITS versus felodipine-ER versus enalapril"

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