Treatment of deep venous thrombosis in pregnant women.

The recommended dosage of tinzaparin in the treatment of thromboembolism during pregnancy is 175 IU/kg/day, as for non-pregnant subjects. In clinical practice, we have experienced a need for a higher dosage, especially in the initial phase of the treatment of deep vein thrombosis, based on four-hour post-dose measurements of anti-Xa activity. Twenty-two pregnant patients with a confirmed deep venous thrombosis were treated with tinzaparin either in a once- or twice-daily regimen. Four-hour post-dosage plasma anti-Xa activity was measured in 357 sequential blood samples during treatment. An higher dosage than recommended, was required to maintain anti-Xa activity in the target range. We suggest that the starting dosage should be 250 IU/kg/day in a twice-daily regimen, and that the dose in the initial phase be adjusted by daily monitoring of anti-Xa.