A comparison of spirapril and isradipine in patients with diabetic nephropathy and hypertension.

The effects of spirapril and isradipine on blood pressure, urinary albumin excretion and sodium-volume homeostasis in hypertensive insulin-dependent diabetic patients with nephropathy were assessed. Fifteen Type 1 diabetic patients aged 28-53 years with a diabetes duration of 19-37 years were studied. All had hypertension and diabetic nephropathy with a urinary albumin excretion of more than 300 mg/24 h. After a single blind placebo treatment period of 4 weeks the patients were randomly assigned to treatment with the calcium antagonist isradipine SRO 5 mg once daily or the ACE inhibitor spirapril 6 mg once daily for 6 months in a double-blind design. Isradipine lowered ambulatory systolic blood pressure from 152 +/- 12 to 141 +/- 11 mmHg (p < 0.05) and ambulatory diastolic pressure from 91 +/- 9 to 86 +/- 8 mmHg (p < 0.05). The blood pressure lowering effect of spirapril was similar: 156 +/- 13 vs 143 +/- 11 mmHg (p < 0.01) and 90 +/- 4 vs 84 +/- 4 mmHg (p < 0.05). The fractional albumin clearance was unchanged on isradipine but decreased after 6 months treatment with spirapril with on average 20% (p < 0.05). Total body exchangeable sodium decreased on spirapril treatment: 2994 +/- 296 vs 2636 +/- 194 meq/1.73 m2 (p < 0.05) and extracellular volume tended to do so (p = 0.12). On isradipine treatment these parameters remained unchanged. In conclusion both isradipine and spirapril lowered blood pressure in patients with diabetic nephropathy. Only the ACE inhibitor had demonstrable beneficial effects on urinary albumin excretion rate and the sodium-volume expansion seen in these patients.