Medical Pharmacology: Immunopharmacology (Immunosuppressant/Immunomodulator) Practice Questions

Azathioprine (Imuran, Azasan):
1. Is a precursor to 6-mercaptopurine (6-MP)
2. Activated by hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
3. Both
4. Neither
Azathioprine is classified as a purine antimetabolite
1. True
2. False
Azathioprine:
1. Prodrug of mercaptopurine
2. Mercaptopurine and additional metabolites are considered prototypes for the antimetabolite class of immunosuppressive agents exhibiting cytotoxicity.
3. Both
4. Neither
Azathioprine:
1. Upon absorption, azathioprine is converted nonenzymatically to 6-mercaptopurine and S-methyl-4-nitro-5-thioimidazole.
2. About 90% of an azathioprine dose is converted to 6-mercaptopurine
3. Both
4. Neither
6-mercaptopurine derived from azathioprine:
1. Converted to other metabolites which inhibit purine synthesis.
2. For example 6-thio-IMP is converted to 6-thio-GMP and then to 6-thio-GTP the latter of which is incorporated into DNA.
3. Both
4. Neither
Azathioprine pharmacokinetics:
1. Well absorbed orally
2. Maximum blood levels noted between 1-2 hours following drug administration.
3. Both
4. Neither
Half-life for azathioprine is about 10 minutes compared to the 60 minute half-life of 6-mercaptopurine.
1. True
2. False
Azathioprine inactivation
1. Xanthine oxidase dependent
2. Patients receiving allopurinol (hyperuricemia control) may require azathioprine dose reduction to prevent excessive toxicity.
3. Both
4. Neither
Azathioprine/mercaptopurine clinical use(s):
1. Maintenance of kidney allograft
2. Useful in treating multiple sclerosis, Crohn's disease, renal aspects associated with systemic lupus erythematosus.
3. Both
4. Neither