Aim: Pharmacodynamic effects of the low molecular weight heparin tinzaparin on plasma levels of tissue factor pathway inhibitor (TFPI) and nitric oxide (NO) were compared in obese subjects, as well as in normal healthy controls.
Methods: Obese (n = 13) patients received a single 75 IU/kg SC injection (the deep vein thrombosis prophylaxis dose) of tinzaparin. Blood samples were obtained pre- and postadministration of drug and at different intervals over 24 h and assayed for total TFPI and NO stable metabolites (nitrates and nitrites) plasma levels, using a specific immunoassay and calorimetric methods.
Results: Mean maximum plasma TFPI levels approached 150-230 ng/ml at the 0.8 h and up to 5 h posttinzaparin dose compared to basal TFPI levels of 35-90 ng/mL. Plasma TFPI levels were still about 2-fold above basal levels at 12 h and fell to basal levels at 16 h after tinzaparin dose. Basal plasma levels of NO, but not TFPI, were significantly lower (P < 0.01) in obese patients compared to controls. Similar TFPI (3-fold above basal at peak) and NO pharmacodynamic profiles for tinzaparin at 75 anti-Xa IU/kg were demonstrated in obese and in normal healthy subjects. Plasma NO (nitrate + nitrite) showed a lag time of about 5-6 h posttinzaparin followed by a steady increase with a peak at 12-15 h and slow decline with a significant residual level at 24 h in obese and healthy subjects.
Conclusions: Data suggest a normal responsiveness of vascular endothelial cells and other cellular compartments to tinzaparin with regard to the pharmacodynamic profiles of plasma TFPI and NO in obese subjects.