Allopurinol was first used to shift the metabolism of thiopurine compounds from 6-MMP to 6-TGN in poor responders to AZA or 6-MP
Afterward, the patient remained on 6-MP
therapy at the decreased dose of 50 mg/day, and aminotransferase levels normalized 1 month after the biopsy.
The incidence of prematurity was about 70% higher among the women treated with azathioprine or 6-MP
, compared with another control group of healthy women who were not treated with the drug.
The selection of AZA or 6-MP
and the dosage of the drug were at the discretion of the clinician.
Measurement of TPMT activity before treatment with AZA or 6-MP
is therefore advisable and cost-effective (38).
Probably safe drugs: 6-MP
, azathioprine, ciprofloxacin, metronidazole, and cyclosporine.
It is not completely clear in the latter study whether all patients were on aza or whether some took 6-MP
In one patient series, IBD patients with impaired TPMT activity accounted for half of all cases of leukopenia and 27% of all cases of severe myelosuppression during 87 months of 6-MP
or azathioprine therapy
Thiopurine methyltransferase (TPMT) inactivates 6-MP
is the analog of hypoxanthine, and azathioprine is a 6-MP
The methyl 6-MP
(Me6-MP) formed was measured using a modification of the HPLC procedure described previously (14).
67), which catalyzes the conversion of a methyl moiety from S-adenosyl methionine to 6-MP
, yielding 6-methyl-MP.