Microdialysis sampling for investigations of tetramethylpyrazine following transdermal and intraperitoneal...

The pharmacokinetic behaviors of tetramethylpyrazine (TMP) were investigated in rat plasma and microdialysates of various sites such as brain, blood and skin after tetramethylpyrazine hydrochloride (TMPH) transdermal or intraperitoneal (i.p.) administration. Samples were collected at timed intervals for the measurement of TMP by a quick and sensitive HPLC-UV method. The pharmacokinetic parameters were calculated by non-compartmental analysis using DAS 2.0. The results of pharmacokinetics indicated that the Cmax in brain and plasma after transdermal administration (20 mg/cm(2), 1.2 cm(2)) was similar to that after i.p. administration (40 mg/kg). The value of Cmax after i.p. administration in brain, blood microdialysates and plasma were 8.17 ± 2.06, 11.58 ± 2.66 and 15.54 ± 3.87 mg/l, respectively. After gel transdermal administration, the value of Cmax in brain, blood, skin microdialysates and plasma were 7.29 ± 2.65, 8.53 ± 1.98, 43.39 ± 29.57 and 15.50 ± 2.99 mg/l, respectively. Compared with traditional administration, gel transdermal administration is a promising alternative to transport TMP to the brain.