Renal responses to nifedipine and captopril in hypertensive insulin-dependent diabetic men: a randomized cross-over study.

The effects of nifedipine retard and captopril on renal haemodynamic parameters have been examined in a double blind randomised cross-over trial in 10 insulin-dependent diabetic males with hypertension (systolic pressure > 150 mmHg or diastolic pressure > 90 mmHg). The acute renal haemodynamic response to nifedipine retard 20 mg and captopril 25 mg was monitored at the start of therapy and again after 8 weeks treatment with nifedipine retard 20 mg b.d. and captopril 25 mg b.d. Blood pressure fell from 148/97 +/- 4/2 (SEM) during the run-in phase to 135/87 +/- 4/1.5 on nifedipine retard and to 131/83 +/- 5/1 on captopril. There was no difference between the initial renal response to the two agents; an increase in renal plasma flow and a non-significant decline in glomerular filtration rate resulted in similar decreases in filtration fraction. After 8 weeks therapy, neither drug had a significant effect on urinary albumin excretion. Baseline renal function did not differ and no acute changes in renal haemodynamics were seen after nifedipine. Following captopril there was no acute change in systemic blood pressure but RPF rose from 572 +/- 41 to 638 +/- 42 ml/min per 1.73 m2 (P < 0.05) and filtration fraction fell from 0.21 to 0.16 (P < 0.02). This sustained acute response of the renal circulation to angiotensin-converting enzyme (ACE) inhibition after chronic therapy may be relevant to the apparent renal protection afforded by ACE inhibitors in experimental nephropathies.