In vivo activity of the 6 -amidinopenicillanic acid derivative, mecillinam, chemically linked or combined in varying ratios with 6-aminopenicillanic acid derivatives

The combination of mecillinam with amoxicillin, ampicillin or penicillin G in a 1 : 1 proportion whether as a mixture or chemically linked ester provides a broader in vivo spectrum of coverage against Gram-positive and Gram-negative bacteria than either component alone. In addition to an increased antibacterial spectrum, the activity seen was at least equivalent to that of the more active component and in a number of instances synergistic in nature. Most often, synergy was noted when the ratio of a penicillin, or cefazolin to mecillinam was from 1 : 1 to 10 : 1.