Allopurinol
Severe
Textbook
Increased 6-mercaptopurine levels and toxicity.
The dose of 6-mercaptopurine should be reduced to 1/3rd.
Source: KDT 7e · p217
Drug reference
6-mercaptopurine
Thiopurine drug
Thiopurine drugATC null
CDSCO approved
EXCRETION
—
not curated
INTERACTIONS
1 major
SEVERE in our sources
PREGNANCY
X
FDA category + note
Top interactions
- AllopurinolSevereTextbookKDT 7e · p217
Mechanism
6-mercaptopurine (6-MP) serves as a prodrug metabolized by hypoxanthine guanine phosphoribosyl transferase (HGPRT) to 6-thioguanine nucleotides (6-TGNs), which are incorporated into DNA and RNA, resulting in arrest of DNA replication and cytotoxicity. TPMT is responsible for the detoxification of 6-MP.
Indications
Inflammatory bowel diseaseAutoimmune disorders (e.g., systemic lupus erythematosus, rheumatoid arthritis)Childhood acute lymphoblastic leukemiaCrohn’s diseasecancer
Pharmacokinetics
Metabolism
Undergoes S-methylation catalyzed by thiopurine methyltransferase (TPMT) for detoxification.
Contraindications
- Genetic deficiency in thiopurine methyltransferase (TPMT) (risk of severe toxicities)
Side effects
Serious
- severe bone marrow toxicity (with thiopurine methyl transferase (TPMT) deficiency)
Pregnancy & lactation
Pregnancy
X
Drug interactions
Related guidelines
Other Unclassified drugs
Ask House about 6-mercaptopurine
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Goodman & Gilman 14e·Verified: 2026-05-10 · House clinical team