Summary
In vivo heparin concentrations and half-life were estimated in 20 human subjects,
after a single intravenous injection.
The method, used for heparin determination, is based on the activated partial thromboplastin
time. The test plasmas are diluted in plasma of the same subject obtained before heparin
administration. In this way the heparin concentrations are reduced to measurable levels
between 0.1 I. U./ml and 0.8 I. U./ml. Indeed a linear relationship between log activated
partial thromboplastin time and heparin concentrations from 0.1 to 0.8 I. U./ml can
be computed. Different half-lives were found in 13 of the 20 subjects examined when
different dilution factors were used. This seems an important limitation for the examination
of the pharmacokinetics of heparin.
