Human blood preservation: effect on in vitro protein binding.

In vitro plasma protein binding for phenytoin, meperidine, and bretylium tosylate was affected by the type of preserved human blood used for its estimation. Fresh heparinized plasma and serum gave equivalent fractions bound at the concentrations studied for all three drugs. However, the in vitro plasma binding of phenytoin and meperidine decreased 9-50% when estimated in fresh citrated plasma or commercially available lyophylized human serum at the concentration levels investigated. The fraction of bretylium tosylate bound to plasma protein decreased 30-40% when estimated in fresh citrated plasma but was unchanged when estimated in the lyophylized human serum.