Abstract: An injectable composition is described having a higher residual effect with reduced detrimental effects such as pain at injection site, swelling, tissue irritancy or necrosis. The composition contains as active principle a tetracycline compound, either as the free base or a salt thereof with a physiologically acceptable acid, complexed with a substantially equimolar amount of a magnesium compound, and is solubilized in a water miscible solvent system comprising glycerol formal in a an amount of about 40 (v/v); with from about 1% to about 20% (v/v) polyethylene glycol and optionally containing a pH modifier in an amount sufficient to maintain a physiologically acceptable pH. In addition, the composition may further comprise a thickener, such as polyvinyl in an amount of about 10% (w/v). The balance of the composition comprises water.

Abstract: An injectable composition of higher residual effect with reduced detrimental effects such as pain at injection site, swelling, tissue irritancy or necrosis and containing as active principle a tetracycline compound, either as the free base or a salt thereof with a physiologically acceptable acid, complexed with a substantially equimolar amount of a magnesium compound, is solubilized in a water miscible solvent system comprising, either (i) a) glycerol formal in an amount of from about 10 to 50% v/v; with b) polyethylene glycol in an amount of from about 1 to 15% v/v; or (ii) from about 25 to about 75% v/v of N-methylpyrrolidone, the composition optionally containing a pH modifier in an amount sufficient to maintain a physiochemically acceptable pH, the balance being made up with water q.s.