[Loss of intravenous nitroglycerin administered with polyvinyl chloride infusion systems]

To evaluate the consequences of the interaction between intravenous nitroglycerin (NTG) and infusion systems made of polyvinyl chloride (PVC), 20 dilutions of NTG were prepared in glass bottles with an initial concentration of 200 micrograms/ml, which were infused through 20 infusion systems at a rate of 20 ml/hour during 12 hours. NTG concentrations collected at the terminal part of the infusion systems were evaluated after 5 minutes, 6 hours and 12 hours. The results showed a substantial loss of NTG through PVC systems. The loss was 20% after 5 minutes and up to 32% after 12 hours. These results, obtained with a preparation similar to that used in clinical practice, may be helpful to estimate the real dose of the infused drug.