Interactions between aminoglycoside antibiotics and carbenicillin or ticarillin

Carbenicillin or ticarcillin were incubated individually with each of the following antibiotics: gentamicin, tobramycin, sisomicin, amikacin. The residual activity of each aminoglycoside in this mixture was assayed enzymatically. Amikacin was inactivated the least of the aminoglycosides. Both penicillins inactivated each aminoglycoside to a similar extent by a degree which varied according to the medium of incubaiton, the least inactivation being seen in pooled human serum and the most in phosphate buffer at pH 7.4.