Pharmacokinetics of S-adenosyl-L-methionine in healthy volunteers.

S-Adenosyl-L-methionine (AdoMet) kinetics was studied in 6 male subjects given 100 and 500 mg i.v. Drug concentrations in plasma and urine were assayed using a radioenzymatic method. Pharmacokinetic parameters were estimated according to an open two-compartment model. The apparent volumes of distribution after the 100 and 500 mg doses were 407 +/- 27 and 443 +/- 36 ml/kg (mean +/- SEM), terminal half-lives 81 +/- 8 and 101 +/- 7 min and body clearances 3.7 +/- 0.5 and 3.1 +/- 0.2 ml/min per kg. Urinary excretion was 34 +/- 3 and 40 +/- 2% of the administered dose. The results demonstrate that drug disposition occurs more via metabolism than via renal excretion, and it is not dependent on the administered dose. Binding of AdoMet to serum proteins is negligible.