Pharmacokinetic studies of tramadol′s analgesic action in mice

Objective To determine pharmacokinetic data of tramadol in mice.Methods Using a united pharmacodynamic pharmacokinetic model,the analgesic action of tramadol was quantified by detecting the number of twisting motion in mice after coelo injection of acetic acid.The pharmacokinetic parameters were determined by observing the time effect and dose effect relationship of tramadol.Results Notable dose effect and time effect relationship of tramadol′s analgesia was seen in mice,its effective dose half life (T 1/2ED ) was 4 68 min;elimination rate constant (K) was 0 148.Conclusion Tramadol itself and its several metabolites have similar analgesic action,the method with united pharmacodynamic pharmacokinetic model is more efficient than those conventional ones which only detect tramadol′s blood level,while this method could reveal the pharmacodynamic changes of tramadol in each target locus.