Photodegradation of furosemide solutions.

Photodegradation of furosemide was studied under the influence of fluorescent and UV lights. Photodecomposition of furosemide solutions appeared to follow first-order kinetics. The compound was found to be most stable at an optimum pH of 7. Long-wave UV light caused the fastest rate of degradation of furosemide. Glutathione, thiourea, EDTA, sodium thiosulfate, sodium metabisulfite, glycine, sodium benzoate and uric acid were found to be ineffective as photoprotective agents. Increase in ionic strength did not cause any change in the degradation rate constant. Amber glass vials and transparent glass vials covered with aluminum foil offered complete protection against fluorescent light. A vehicle consisting of a mixture of 50% (v/v) propylene glycol in phosphate buffer offered slight photoprotection.