Studies on photohemolysis with special reference to demethylchlortetracycline.

Hemolysis induced by ultraviolet radiation as well as demethylchloretetracycline (DMCT) phototoxicity have been investigated in a model using human red blood cells. Total hemolysis for UV-B and UV-C was obtained with 8.3 and 1.9 J/cm2 respectively. DMCT was shown to have pronounced hemolytic properties causing 88% hemolysis at 50 micrograms/ml and 72 J/cm2 of UV-A. No increased hemolysis rate was seen in combination with UV-B. Several factors influencing the results were studied such as incubation time, UV-A dose, drug concentration and different methods for hemoglobin detection. Photohemolysis is an accurate tool for demonstrating DMCT phototoxicity.