Stability of chlortetracycline hydrochloride and chloramphenicol in some ophthalmic ointment bases

The stability of chlortetracycline hydrochloride at 25 and 35 degrees C in absorption base with and without antioxidant decreased during storage for 12 months, while, in water-in-oil emulsion base the medicament was more stable than in oil-in-water emulsion ointment bases. Chloramphenicol was more stable in the absorption base that contained lanolin than in the base which contained cetyl alcohol. Chloramphenicol was more stable in oil-in-water than in water-in-oil emulsion bases. The decomposition rate constant of chlortetracycline hydrochloride and chloramphenicol followed first order kinetics, when the stability study was carried out at 25 and 35 degrees C.