Intravenous infusions of heparin and penicillins

The chemical stability and anticoagulant activity of heparin (20 U/ml) were studied in five intravenous fluids at room temperature. Heparin remained stable and active for 24 hours in normal saline, but there was a rapid inactivation of 40 to 55% in solutions containing dextrose or lactate, as measured by chemical and biological methods.High concentrations of benzylpenicillin, ampicillin, or methicillin had no effect on heparin activity in normal saline or dextrose 5%: nor was the stability of the penicillins in these fluids affected to any marked extent by the presence of heparin. Ampicillin was, however, found to be unstable in dextrose 5%, and it would be preferable for it not to be added to dextrose infusions. It is concluded that heparin may be given intravenously in normal saline with benzylpenicillin, ampicillin, or methicillin but several other antibiotics were found to be unsuitable for concurrent infusion with heparin.