SERUM RETINOIDS IN RETINITIS-PIGMENTOSA PATIENTS TREATED WITH VITAMIN-A

Background: Patients with retinitis pigmentosa have been suggested to benefit from treatment with moderate doses of retinyl palmitate. Retin yl palmitate is not an active retinoid in itself but is metabolised to active components in the body. To find out which metabolites of retin yl palmitate were formed and at which concentrations, we measured the concentrations of retinol, retinyl palmitate, retinoic acids and tocop herol in serum of patients treated with oral retinyl palmitate for ret initis pigmentosa. Methods: Nine male patients and one female diagnose d as having retinitis pigmentosa after a complete ophthalmological exa mination including a full-field electroretinogram were given vitamin A at their own request as one daily morning dose of 16 600 IU vitamin A . Blood samples were obtained before and after >2 weeks of treatment. The concentrations of retinoids and tocopherol were measured with esta blished methods. Results: The patients were not deficient in vitamin A or vitamin E as judged from the serum vitamin concentrations. Treatme nt with retinyl palmitate significantly increased the serum concentrat ion of retinyl palmitate and of 13-cis-retinoic acid but not of retino l, tocopherol or all-trans-retinoic acid. Conclusions: Neither retinyl palmitate nor 13-cis-retinoic acid, are known to be biologically acti ve. However, 13-cis-retinoic acid can isomerise to the active vitamin A derivative, all-trans-retinoic acid. It is suggested that patients m ay be treated with a small dose of 13-cis-retinoic acid instead, to av oid the relatively long metabolic detour from retinyl palmitate.