Azathioprine

Absorption	Well absorbed following oral administration.
Volume of distribution	Not Available
Protein binding	Azathioprine and the metabolite mercaptopurine are moderately bound to serum proteins (30%).
Metabolism	Primarily converted to the active metabolites 6-mercaptopurine and 6-thioinosinic acid via a non-enzymatica process. 6-mercaptopurine is subsequently metabolized primarily by xanthine oxidase. Enzyme Metabolite Reaction Km Vmax Thiopurine S-methyltransferase S-methylazathioprine S-methylation
Route of elimination	Not Available
Half life	Approximately 5 hours for the unchanged drug and its metabolites.
Clearance	Not Available
Toxicity	The oral LD50 for single doses of azathioprine in mice and rats are 2500 mg/kg and 400 mg/kg, respectively. Very large doses of this antimetabolite may lead to marrow hypoplasia, bleeding, infection, and death.
Affected organisms	Humans and other mammals