Antibiotic compatibility and stability in a parenteral nutrition solution.

Eight antibiotics, alone and in selected combinations, were evaluated for stability and compatibility in a protein hydrolysate parenteral nutrition solution. Samples were stored under varying conditions and evaluated at 12-hour intervals over a period of 24--48 h. Compatibility and stability were assessed by quantitative bacteriologic assay, pH determinations and visual inspection. In most cases, antibiotics were compatible and stable over the entire study period. Carbenicillin, methicillin in combination with gentamicin, and tobramycin in combination with cephalothin or methicillin, exhibited a gradual loss of antibacterial activity after 24 h. These results indicate that the antibiotics studied may be administered in protein hydrolysate parenteral nutrition solutions. This mode of therapy offers a means of combating infection, while maintaining a nutritional source for host defences, tissue repair, and growth.