Pharmacokinetics of Oral Taurine in Healthy Volunteers

Taurine, a sulfur-containing amino acid, is a normal constituent of the human diet. Little is known of the pharmacokinetics of taurine in man after oral administration. We studied the pharmacokinetics of 4？g taurine in eight healthy male volunteers (median age 27.5, range 22–45) following orally administration in the fasting state in the morning. Blood samples were taken at regular intervals and plasma taurine concentration was measured by a modified HPLC method. Data were subjected to noncompartmental analysis. Maximum plasma taurine concentration ( ) was measured at ？hr after administration as ？mg/L ( ？mmol). Plasma elimination half-life ( ) and the ratio of clearance/bioavailability (Cl/F) were ？hr and ？L/hr, respectively. Since taurine is occasionally used in therapeutics as a medicine, the pharmacokinetics and effects of oral taurine in healthy volunteers would be useful in the future studies of taurine in pharmacology and nutrition. 1. Introduction Taurine, a sulfur-containing amino acid, is a relatively nontoxic substance and a normal constituent of the human diet [1]. The diet provides most taurine either directly or by synthesis in the liver and brain from methionine or cysteine via cysteic acid or hypotaurine [2] or via cysteamine in the heart and kidney. Taurine stabilises membranes, modulates calcium transport, and is able to dissipate the toxic effects of hypochlorous acid (HOCl) by the formation of the relatively stable taurochloramine molecule, generated by myeloperoxidases from oxygen radicals. The ability of taurine to conjugate with xenobiotics, retinoic acid, and bile salts and its role as a major free amino acid in regulating the osmolality of cells are also examples of protective functions [3]. Obinata et al. showed ALT concentrations recovering in children with fatty liver after 6-months treatment with oral taurine administered daily [4]. Protective effects of taurine against arteriosclerosis [5], lung injury by oxidant gases [6], deleterious effects of various drugs such as tauromustine, an antitumor agent, [7], hepatotoxicity of sulfolithocholate [8], and its promotion of the recovery of leukocytes in irradiated rats [9] have already been studied on animals. The therapeutic effects of taurine on epilepsy [10], ischemia [11], obesity [12], diabetes [13], hypertension [14], Congestive heart failure [15], noxious effect of smoking [16], toxicity of methotrexate [17] myocardial infarction [18], alcoholic craving [19], and neurodegeneration in elderly [20] have also been reported. Taurine may protect membranes by detoxification of