Abstract: The present invention relates to a new compounded composition with synergistic properties, to dosage units thereof, and to the use of the said compounded composition and dosage units.The composition contains as active ingredients the amidinopenicillanic acid mecillinam or a pharmaceutically acceptable, non-toxic salt or pro-drug thereof in combination with another antibiotic compound of the formula ##STR1## or a pharmaceutically acceptable, non-toxic salt or pro-drug thereof, optionally together with pharmaceutically acceptable, non-toxic carriers and/or auxiliary agents.The new composition is valuable in the human and veterinary practice for the treatment of patients suffering from infectious diseases.

Abstract: The present invention relates to a new pharmaceutical composition with synergistic properties, to dosage units thereof, and to the use of the said composition and dosage units in the human or veterinary practice for the treatment of patients suffering from infectious diseases. The composition contains as active ingredients an amidinopenicillanic acid derivative of the formula ##STR1## in which R is hydrogen or a lower alkanoyloxymethyl radical including the pivaloyloxymethyl radical or atoxic salts thereof in combination with 2,4-diamino-5(3,4,5-trimethoxybenzyl)-pyrimidine, also known under the name trimethoprim, used hereinafter, or atoxic salts thereof.