Psoriasis thioguanine

Thioguanine is a purine analog that has been used as an alternative treatment for psoriasis when conventional therapies have failed. The typical dose is 80 mg twice weekly, increased by 20 mg every 2 to 4 weeks the maximum dose is 160 mg three times a week. Adverse effects include bone marrow suppression, GI complications (e.g., nausea, diarrhea), and elevation of liver fimction tests. 6-Thioguanine may be less hepatotoxic and therefore more useful than methotrexate in hepatically compromised patients with severe psoriasis. 

Thioguanine is a purine analogue structurally related to 6-mercaptopurine and azathioprine. Thioguanine interferes with several enzymes required for de novo purine synthesis, and its metabolites are incorporated into DNA and RNA, further impeding nucleic acid synthesis. The mechanism of action of thioguanine in psoriasis is not clearly understood it has been hypothesized to affect the proliferation and trafficking of lymphocytes as well as the proliferation of keratinocytes. 

Although 6-thioguanine is chiefly used in chemotherapy for acute myelocytic leukemia and other marrow-based malignancies, lower doses are very effective for moderate to severe psoriasis, particularly in... 

Kao NL, Rosenblate HJ. 6-Thioguanine therapy for psoriasis causing toxic hepatic venoocclnsive disease. I Am Acad Dermatol 1993 28(6) 1017-18. 

Murphy FP, Cover TR, Burack LH, et al. Chnical clearing of psoriasis by 6-thioguanine correlates with cutaneous T-cell depletion via apoptosis evidence for selective effects on activated T lymphocytes. Arch Dermatol 1999 135 1495-1502. 

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