ANTIHISTAMINES REDUCE BLOOD-RETINAL BARRIER PERMEABILITY IN TYPE-I (INSULIN-DEPENDENT) DIABETIC-PATIENTS WITH NONPROLIFERATIVE RETINOPATHY - A PILOT-STUDY

Purpose: To determine if histamine receptor stimulation mediates incre ased blood-retinal barrier (BRB) permeability in patients with diabeti c retinopathy, as it does in experimental diabetes. Methods: Fourteen patients with type I (insulin-dependent) diabetes and mild nonprolifer ative diabetic retinopathy were treated with combined astemizole, 20 m g, and ranitidine, 600 mg, or an identical placebo for 6 months in a d ouble-masked fashion, Blood-retinal barrier permeability was measured by vitreous fluorometry at baseline and at 3 and 6 months. Results: Pe rmeability was significantly reduced in the group treated with antihis tamines (P < 0.05) compared with the placebo group, There were no conc omitant significant changes in systemic arterial blood pressure or HbA (1c) values. Conclusion: These pilot data suggest that histamine recep tors influence permeability of the BRB in human diabetes. Further stud ies of the effects of antihistamines on diabetic retinopathy are warra nted.