Effects of sorbinil therapy in diabetic patients with painful peripheral neuropathy and autonomic neuropathy.

Clinical investigations with the aldose reductase inhibitor sorbinil in patients with peripheral neuropathy due to diabetes are described. After an improvement in motor and sensory nerve conduction velocities was demonstrated in asymptomatic diabetic patients taking sorbinil (compared with velocities during a placebo period), 11 patients with painful diabetic neuropathy were treated with sorbinil for three weeks without alterations in diabetic management or control. Therapy was placebo-controlled in a single-blind fashion in eight patients. Pain (assessed by or on a zero to 20 rating scale), which had been constant for many months before entry into the study and unresponsive to numerous medications, improved from a mean score of 16 to 8 and returned when the drug was discontinued. Objective improvement in sensation and strength were observed in some cases. Improvements in nerve conduction velocity and cardiac autonomic function were also documented. Cardiac autonomic neuropathy was studied in 36 patients in a double-blind, placebo-controlled, randomized, noncrossover trial. Patients received one 250-mg sorbinil tablet or one placebo tablet daily for six weeks, after a one-week baseline period. Glycemic control did not change during the study period, as indicated by unaltered glycohemoglobin levels. Response was assessed by expiration-inspiration ratios, obtained on electrocardiography during six cycles per minute respiration, and by resting minimal heart rate, both measures of vagal function. In the sorbinil-treated group, expiration-inspiration ratios improved from 1.074 +/- 0.012 to 1.096 +/- 0.020 (p less than 0.03). There was a slight decrease in the ratios in the placebo-treated group, from 1.112 +/- 0.023 to 1.105 +/- 0.023 (not significant). The difference between the Week 0 to Week 6 changes in each group was significant (p less than 0.01). Resting minimal heart rate decreased in the sorbinil-treated group from 76.4 +/- 2.3 to 66.8 +/- 2.8 +/- 2.4 beats per minute (p less than 0.001), with a mean change of 10 +/- 2. In the placebo-treated group, heart rate was unchanged (77.9 +/- 3.9 to 77.5 +/- 3.3 beats per minute). The two-sample t test of the within-group differences was also significant (p less than 0.001). The changes in both expiration-inspiration ratios and resting minimal heart rate are consistent with a sorbinil-related improvement in cardiac parasympathetic nerve function. Several isolated cases of apparent sorbinil-related improvements in autonomic symptoms have been observed.(ABSTRACT TRUNCATED AT 400 WORDS)