The effect of simultaneous intravenous administration of nitroglycerin and heparin on partial thromboplastin time.

The purpose of this study was to determine whether intravenous nitroglycerin, when infused simultaneously through the same tubing with heparin, alters the anticoagulant effect of heparin as evidenced by partial thromboplastin time (PTT) values. A time series, cross-over design was used. The study included patients admitted to the Coronary Care Unit with a diagnosis of unstable angina. Patients were randomly assigned to one of two treatment groups: (1) heparin/nitroglycerin infused in the same site or (2) heparin/nitroglycerin infused in separate sites. After 18 hours, treatments were reversed. PTT results were measured seven times per subject. Ninety-eight subjects, 70 males and 28 females, participated. Mean age was 62.4 +/- 9 years. Using repeated measures analysis of variance, there was no change in the patients' PTTs (p = 0.47). Prior to this study, research was divided on whether nitroglycerin interferes with heparin's activity. This study indicates no significant difference in PTT in subjects receiving these infusions via separate or the same intravenous sites.