Stability of oxytetracycline hydrochloride in eye-drops, prepared in pharmacies.

In the ophthalmological practice the so-called "Oxytetracycline-eye-drop" is frequently used, prepared in pharmacies ex tempore with a short self-life (3 days). In this paper a TLC-densitometric method is described for the determination of the degradation products of oxytetracycline HCl (OTC) formed in the "Oxytetracycline-eye-drop". A chloroform-methanol-water (65 + 25 + 5 v/v) solvent system is applied on silica gel TLC plate, predeveloped with saturated disodium ethylenediamine-tetraacetate aqueous solution. UV densitometry at 254 nm is used for quantitative determination. The chemical stability of OTC in different eye-drops as well as the effects of the pH and the mode of the preparation and storage conditions on the decomposition process are discussed.