ANTIHISTAMINES REDUCE BLOODRETINAL BARRIER PERMEABILITY IN TYPE I (INSULIN-DEPENDENT) DIABETIC PATIENTS WITH NONPROLIFERATIVE RETINOPATHY

PURPOSE To determine if histamine receptor stimulation mediates increased blood-retinal barrier (BRB) permeability in patients with diabetic retinopathy, as it does in experimental diabetes. METHODS Fourteen patients with type I (insulin-dependent) diabetes and mild nonproliferative diabetic retinopathy were treated with combined astemizole, 20 mg, and ranitidine, 600 mg, or an identical placebo for 6 months in a double-masked fashion. Blood-retinal barrier permeability was measured by vitreous fluorometry at baseline and at 3 and 6 months. RESULTS Permeability was significantly reduced in the group treated with antihistamines (P < 0.05) compared with the placebo group. There were no concomitant significant changes in systemic arterial blood pressure or HbA1c values. CONCLUSION These pilot data suggest that histamine receptors influence permeability of the BRB in human diabetes. Further studies of the effects of antihistamines on diabetic retinopathy are warranted.