Investigation of stability of tetracycline hydrochloride in methylcellulose gel.

The investigations proved that granulation of tetracycline hydrochloride with ethanol, methanol or acetone does not reduce the antibiotic activity of the preparation. At room temperature the activity of the granular preparation decreases by 10% within the time range from 994 to 1074 d. Gel containing 0.7% of methylcellulose, 5% of 1,2-propylene glycol and 5% of dimethyl acetamide proved to be very stable in respect to viscosity and pH over 3 years. Application of 20% excess of tetracycline hydrochloride and storage of the gel at 4 degrees C enables maintaining it active over 21 d.