The Formulation Of Stable Adrenaline Eye Drops For Use In The Management Of Glaucoma

Abstract

The different factors affecting the stability of adrenaline in solution have been examined with a view to producing a pharmaceutically active eye drop prep~ration of adrenaline. It was important that such a formulation should be simple enough to

enable preperation using the available facilities in this country_ A preformu1ation screening of antioxidants in the pH absence of adrenaline showed that at low/values (around pH 3.0) sodium sulphite was superior to either sodium metabisu1phite or ascorbic acid. Accelerated stability studies showed that the pH of maximum stability for aqueous solutions of adrenaline was approximately pH 3.7. Accelerated stability tests at this pH

confirmed the superiority of sodium sulphite over a combination of sodium metabisu1phite and ascorbic acid as antioxidants. Accelerated stability studies also confirmed the important role of boric acid in enhancing the stability of adrenaline in aqueous solutions. An investigation of four sterilization procedures showed that the immediate loss of adrenaline was negligible after either sterilization by filtration or by heating at 980c for 30 minutes. Higher sterilization temperatures caused substantial loss of adrenaline and discolouration of the solut ions , For reasons of comfort to the patient on instillation - 131 - into the eye and for clarity of the solution in presence of the preservative used (Benzalkonium Chloride), a final formulation of adrenaline eye drops was prepared in borate buffer at pH 5.8, with sodium sulphite as the antioxidant. Accelerated stability studies and long term storage studies at ambient temperatures showed that the final preparation was reasonably stable. Clinical testing of the preparation on hospitalized glaucoma patients showed that the preparation compared favourably with commercial and other preparations used in the management of raised intraocular pressures.