Resources
Thioguanine
- 80 mg/day if normal thiopurine methyltransferase (TPMT) level (given orally but absorption incomplete/unpredictable)
- Belong to thiopurine family, & has a mechanism of action + metabolism similar to azathioprine
- Pregnancy Category D
- Thioguanine not metabolized by xanthine oxidase, so thiopurine methyltransferase (TPMT) significantly involved in clearing
- Prodrug, converted in liver to 6-thioguanilyic acid (similar active metabolite of azathioprine), yields nucleoside analogues that produce cytotoxic effects via incorporation into DNA (deoxyribonucleic acid) during S phase of cell cycle
- Affects primarily activated T lymphocytes
Food & drug administration (FDA)
- Acute non-lymphocytic leukemia
Off label
- Psoriasis
- Dermatitis
- Severe atopic dermatitis
- Connective tissue disease
- Cutaneous-limited Lupus (very rarely used)
Absolute
- Hypersensitivity
- Pregnancy
- Lactation
Relative
- History of hepatovenular occlusive disease
- Hematologic disorders
- Active infection
Hematologic
- Myelosuppression (~50%, early sign: thrombocytopenia)
Gastrointestinal
- Nausea, excessive flatulence, taste changes, esophageal reflux, diarrhea
- Hepatitis (rare) & hepatovenular occlusive disease (rare)
Metabolic
- Hyperuricemia
Infectious
- Opportunistic with myelosuppression
- Aminosalicylates (inhibit thiopurine methyltransferase (TPMT) activity) will result in more active compound
Baseline
- History & physical exam
- Complete blood count, chemistry profile, liver function tests, Urinalysis, tuberculin skin test (if indicated), Thiopurine methyltransferase (TPMT) level
Follow-up
- Complete blood count, liver function tests weekly then every 2weeks as dose stabilizes. Once dose stable monthly x3 months then every 3months