Abstract: Studies on the pharmacokineties and bioavailability of tetramethylpyrazine phosphate (TMPP) after intravenous, intramuscular and oral administrations were carried out in comparision with tetramethylpyrazine hydrochloride (TMPH) in dogs. The drug concentration-time curves of both drugs were shown to fit a one compartment open model. The pharmacokinetic parameters were shown in tables 1～3. Better absorption, slower elimination, longer T 1/2 and greater absolute bioavailability of TMPP than those of TMPH were observed after IM administration of the drugs. The absorption of TMPP was more regular than that of TMPH when the drugs were given orally in small doses.TMPP was absorbed relatively completely and distributed in various tissues, especially in the liver. The excretion of unchanged drug in urine and feces was about 1.40% within 36 h after oral administration in rats.