Thiopurine antimetabolite Pregnancy: Tioguanine, like other cytotoxic agents, is potentially teratogenic. Use should be avoided whenever possible during pregnancy, particularly during the first trimester; in each case the potential hazard to the foetus must be balanced against the expected benefit to the mother. Adequate contraceptive precautions should be advised when either partner is receiving tioguanine. Mothers receiving tioguanine should not breast-feed (§4.6).

Tioguanine (Specialist drug)

Tioguanine is an oral thiopurine antimetabolite used chiefly in the treatment of acute leukaemias. It is a specialist drug initiated under haematology supervision.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Usual dosage 100 to 200 mg/m2 body surface area, per day.

Route: Oral

Frequency: Per day, in short-term cycles. The exact dose and duration of administration depend on the nature and dosage of the other cytotoxic drugs given in conjunction with tioguanine. Not recommended for maintenance therapy or similar long-term continuous treatment because of the high risk of liver toxicity.

Absorption is variable and plasma levels may be reduced following emesis or intake of food. TPMT-deficient patients: those with inherited little or no thiopurine S-methyltransferase activity are at increased risk of severe toxicity from conventional doses and generally require substantial dose reduction — the optimal starting dose for homozygous deficient patients has not been established; most heterozygous patients tolerate recommended doses but some require reduction. NUDT15 variant patients (particularly homozygotes) are at increased risk of severe toxicity and generally require dose reduction; genotypic testing may be considered before initiation. In any case close monitoring of blood counts is necessary. PAEDIATRIC (per SPC §4.2): 'Similar dosages to those used in adults, with appropriate correction for body surface area, have been used' — no separate per-kg paediatric dose is stated. Note the SPC §4.4 warning that liver toxicity has been observed in a high proportion of children receiving tioguanine as part of maintenance therapy for acute lymphoblastic leukaemia. Elderly: no specific dosage recommendations; tioguanine has been used in combination chemotherapy schedules in elderly patients with acute leukaemia at equivalent doses to those used in younger patients. Monitoring: blood cell counts and weekly liver function tests; discontinue in patients with evidence of liver toxicity. For use only under the direction of physicians experienced in the administration of cytotoxic agents.

Dose adjustments

Renal

Consideration should be given to reducing the dosage in patients with impaired hepatic or renal function (§4.2).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to tioguanine or to any of the excipients (§4.3)
SPC §4.3 states: 'In view of the seriousness of the indications there are no absolute contra-indications.'

Side effects

Bone marrow failure (very common) — leucopenia and thrombocytopenia; anaemia less frequently
Veno-occlusive liver disease (very common) — hyperbilirubinaemia, tender hepatomegaly, weight gain due to fluid retention and ascites
Portal hypertension (very common) — splenomegaly, oesophageal varices, thrombocytopenia
Stomatitis and gastrointestinal disorder (common)
Hyperuricaemia (common); hyperuricosuria and urate nephropathy (common)
Necrotising colitis and hepatic necrosis (rare)

Interactions

Drugs that inhibit TPMT, such as olsalazine, mesalazine or sulphasalazine — coadministration could exacerbate myelosuppression in patients sensitive to the myelosuppressive effect of tioguanine (§4.4)
Live organism vaccines — immunisation has the potential to cause infection in immunocompromised hosts and is not recommended; patients in remission should not receive live organism vaccines until at least 3 months after chemotherapy has been completed (§4.4)

Clinical monograph

How it works

It is incorporated into nucleic acids as a fraudulent purine, disrupting DNA and RNA synthesis and producing cytotoxicity in dividing cells.

Prescribing in practice

It causes dose-related myelosuppression, so blood counts must be monitored regularly and the dose adjusted to avoid severe cytopenias.
Hepatotoxicity, including veno-occlusive disease and nodular regenerative hyperplasia, can occur, particularly with prolonged use, which limits its long-term role.
TPMT and NUDT15 status influences toxicity risk, and it is teratogenic, so effective contraception is advised.

Monitoring

Monitor full blood count frequently and liver function regularly, watching for signs of hepatic toxicity.

Counselling the patient

Attend for regular blood tests so your dose can be adjusted safely.
Report fever, sore throat, bruising, bleeding, yellowing of the skin or abdominal swelling promptly.
Use reliable contraception during treatment.

Evidence & guidelines

Use is guided by the manufacturer's SPC and specialist haematology protocols, with thiopurine metabolism testing recommended.

Reference: SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways