Assessment of the drug interaction between intravenous nitroglycerin and heparin

To assess whether a clinically significant interaction occurs between heparin and nitroglycerin (NTG). Activated partial thromboplastin time (APTT) was measured in patients with unstable angina who were stabilized on intravenous NTG and heparin just prior to weaning the NTG infusion, and one and four hours after stopping the NTG. In 22 heparin-treated patients (20 men, 2 women; aged 56.7 ± 10 years; weight 79.5 ± 15 kg), the APTT ratio was inversely related to the dose of NTG (slope = −0.003; p<0.05). However, there were no significant differences between the APTT values measured before and after discontinuation of NTG (p=0.8511). Our study demonstrates a clinically insignificant interaction between NTG and heparin at NTG doses commonly used in patients.