In children receiving multiple antibiotics and total parenteral nutrition (TPN), the amount of nutrition received can be less than optimal if the central venous line is used for administration of blood products, antibiotics and other medications. The purpose of this study was to evaluate the compatibility of commonly used antibiotics in our standard hyperalimentation solution to determine whether these drugs could be administered in a "piggyback" fashion with parenteral nutrition. If there were no incompatibility this could allow significantly more TPN to be delivered without need for extra fluid in patients receiving antibiotics several times daily. We found 13 antibiotics (amikacin, azlocillin, cefamandole, cephalothin, gentamicin, mezlocillin, moxalactam, nafcillin, oxacillin, penicillin, piperacillin, ticarcillin and tobramycin) to be stable for 6 hours and compatible with the TPN solution. They could be safely given in the presence of the hyperalimentation preparation (1.5% amino acid, 15% dextrose, vitamins, calcium (300 mg/liter) and standard electrolyte concentrations).