Pharmacokinetics of UH and LMWH are similar with respect to antithrombin activity

LMWHs, as a class of drugs, are no more predictable in antithrombin effect after subcutaneous injection than unfractionated heparin. There were considerable differences among LMWHs in the observed variability of antithrombin effects, with tinzaparin being somewhat more predictable than the other drugs tested.