Abstract: A new HPLC method for the determination of a metabolite of analgin, MAA (4 methylaminoantipyrine), in plasm and its application to determine the bioavailabilities of analgin nasal drops in human volunteers is reported in this paper. A Waters Model 481 instrument was used throughout the experiment. IAA (isopropylaminoantipyrine) was shown to be the most suitable internal standard at absorption wavelength of 254 nm. A mixture of phosphate buffer (pH 5.5) and methanol (68∶32) was used as the mobile phase with a flow rate of 2 ml·min^-1, and YWG-C₁₈ H₃₇ as stationary phase. Calibration curve was linear (γ=0.9998) in the concentration range of 0.1～5 μg·ml^-1. The within day and day to day precision (RSD) of this method were 2.35% and 2.61%, respectively, with average recoveries of 99.3%～103.9%. No interference was found in the body fluid. The plasma samples of healthy volunteers were treated with acid and extracted with ether. The system of mobile phase and the process of blood sample treatment were simpler than those reported in literature. So, the method is suitable for the study of pharmacokinetics and clinical determination of blood level of analgin. The studies on bioavailabilities of analgin nasal drops were carried out in 8 men relative to intramuscular injection and 6 men relative to oral tablets, respectively, at the dose of 250 mg analgin in different preparations administered by cross over method. The main pharmacokinetic parameters were shown in Table 3. The results indicate that analgin nasal drops exhibited a higher bioavailability (relative to injection) and faster absorption (relative to tablet). So, analgin is suitable to be developed as a nasal preparation.