Summary Background Diabetes is a common cause of polyneuropathy. The development and progression of nephropathy, retinopathy, and neuropathy are closely related. Angiotensin-converting enzyme (ACE) inhibitors delay progression of both nephropathy and retinopathy. We investigated the effect of ACE inhibition on diabetic neuropathy. Methods We recruited 41 normotensive patients with type I or type II diabetes and mild neuropathy into a randomised double-blind placebo-controlled trial. Changes in the neuropathy symptom and deficit scores, vibration-perception threshold, peripheral-nerve electrophysiology, and cardiovascular autonomic function, were assessed at 6 and 12 months. The primary endpoint was the change in peroneal nerve motor conduction velocity. Findings We found no significant difference at baseline for age, HbA 10 , blood pressure, or severity of neuropathy between two groups. There was no change in HbA 10 over the treatment period. Peroneal motor nerve conduction velocity (p=0·03) and M-wave amplitude (p=0·03) increased, and the F-wave latency (p=0·03) decreased and sural nerve action potential amplitude increased (p=0·04) significantly after 12 months of treatment with trandolapril compared with placebo. Vibration-perception threshold, autonomic function, and the neuropathy symptom and deficit score showed no improvement in either group. Interpretation The ACE inhibitor trandolapril may improve peripheral neuropathy in normotensive patients with diabetes. Larger clinical trials are needed to confirm these data before changes to clinical practice can be advocated.
