The pharmacokinetics of huperzine A in dogs after single intravenous and oral administrations was investigated. Concentrations of huperzine A were determined by a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Pharmacokinetic parameters were calculated by non-compartmental methods. After single intravenous administration, the Cmax, T1/2, AUC0-t, AUC0-infinity, CL, Vd and Vss were 5.55 +/- 1.61 microg/L, 5.02 +/- 0.31 h, 16.04 +/- 5.24, 16.49 +/- 5.29 microgh/L, 0.66 +/- 0.19 L/h/kg, 4.76 +/- 1.46, and 3.93 +/- 1.54 L/kg, respectively. After single oral administration, the Cmax, Tmax, T1/2, AUC0-t, AUC0-infinity and oral bioavailability were 2.60 +/- 0.60 microg/L, 1.25 +/- 0.50 h, 5.71 +/- 2.25 h, 12.90 +/- 3.19, 13.78 +/- 3.24 microgh/L, and 94.4 +/- 36.5%, respectively. In conclusion, huperzine A had a rapid and nearly complete oral absorption and was extensively distributed into tissues after drug administration in dogs.