Astemizole reduces blood-retinal barrier leakage in experimental diabetes.

We examined the potential of astemizole, a histamine H1-receptor antagonist that does not cross the blood-brain barrier, to reverse blood-retinal barrier leakage to albumin in streptozotocin diabetic rats. Four groups of nondiabetic and four groups of diabetic rats received vehicle or astemizole at dosages of 5, 10, or 20 mg/kg body weight for days 22-28 of a 28-day holding period. There were no significant differences in nondiabetic plasma-vitreous albumin ratios between animals receiving vehicle or any of the three astemizole dosages. Only diabetic rats receiving vehicle showed a significant (p < 0.05) 100% increase in the plasma-vitreous albumin ratio over their nondiabetic counterparts. Diabetic rats receiving either 5, 10, or 20 mg/kg astemizole exhibited total normalization of vitreous albumin accumulation, despite persistence of diabetes. These data indicate that astemizole, an H1-receptor antagonist that does not cross the blood-retinal barrier, is effective in reversing blood-retinal barrier leakage of albumin in experimental diabetes.