Antihypertensive and renal effects of enalapril in post-transplant hypertension

The acute and chronic antihypertensive and renal effects of the angiotensin converting enzyme inhibitor, enalapril, were studied prospectively in ten hypertensive renal transplant recipients. Acute administration of enalapril produced a significant decrement in both systolic and diastolic blood pressure but had no significant effect on glomerular filtration rate or effective renal plasma flow. The antihypertensive effect of enalapril was enhanced by gradually increasing the dose of the drug or by addition of a diuretic during six to eight weeks of chronic therapy. During chronic enalapril therapy, four patients developed renal insufficiency that reversed after discontinuation of the drug. In three of these four cases, overt renal insufficiency was associated temporally with the addition of a diuretic. Digital angiography revealed unequivocal transplant renal-artery stenosis in three of the four patients with renal insufficiency; the fourth patient had diffuse narrowing of the transplant renal artery without a discrete stenosis. It is concluded that enalapril alone or in combination with a diuretic is effective in lowering blood pressure in patients with post-transplant hypertension. The development of renal insufficiency during enalapril therapy may be exacerbated by concomitant diuretic therapy and should raise the suspicion of underlying transplant renal-artery stenosis. The acute blood pressure or renal response to a small dose of enalapril does not reliably predict the development of renal insufficiency during treatment with larger doses of the drug.