Purinetone Drug Interactions

Vaccinations with live organism vaccines are not recommended in immunocompromised individuals.
The administration of 6-mercaptopurine with food may decrease systemic exposure slightly. 6-mercaptopurine may be taken with food or on an empty stomach, but patients should standardise the method of administration to avoid large variability in exposure. The dose should not be taken with milk or dairy products since they contain xanthine oxidase, an enzyme which metabolises 6-mercaptopurine and might therefore lead to reduced plasma concentrations of mercaptopurine.
Effect of concomitant medicinal products on 6-mercaptopurine: Ribavirin: Ribavirin inhibits the enzyme, inosine monophosphate dehydrogenase (IMPDH), leading to a lower production of the active 6-thioguanine nucleotides. Severe myelosuppression has been reported following concomitant administration of a pro-drug of 6-mercaptopurine and ribavirin; therefore concomitant administration of ribavirin and 6-mercaptopurine is not advised.
Myelosuppressive agents: When 6-mercaptopurine is combined with other myelosuppressive agents caution should be used; dose reductions may be needed based on haematological monitoring.
Allopurinol/oxipurinol/thiopurinol and other xanthine oxidase inhibitors: Xanthine oxidase activity is inhibited by allopurinol, oxipurinol and thiopurinol, which results in reduced conversion of biologically active 6-thioinosinic acid to biologically inactive 6-thiouric acid. When allopurinol, oxipurinol and/or thiopurinol and 6-mercaptopurine are administered concomitantly it is essential that only 25% of the usual dose of 6-mercaptopurine is given.
Other xanthine oxidase inhibitors, such as febuxostat, may decrease the metabolism of 6-mercaptopurine. Concomitant administration is not recommended as data are insufficient to determine an adequate dose reduction.
Aminosalicylates: There is in vitro and in vivo evidence that aminosalicylate derivatives (e.g. olsalazine, mesalazine or sulfazalazine) inhibit the TPMT enzyme. Therefore, lower doses of 6-mercaptopurine may need to be considered when administered concomitantly with aminosalicylate derivatives.
Methotrexate: Methotrexate (20 mg/m² orally) increased 6-mercaptopurine AUC by approximately 31% and methotrexate (2 or 5 g/m² intravenously) increased 6-mercaptopurine AUC by 69 and 93%, respectively. Therefore, when 6-mercaptopurine is administered concomitantly with high dose methotrexate, the dose should be adjusted to maintain a suitable white blood cell count.
Infliximab: Interactions have been observed between azathioprine, a pro-drug of 6-mercaptopurine, and infliximab. Patients receiving ongoing azathioprine experienced transient increases in 6-TGN (6-thioguanine nucleotide, an active metabolite of azathioprine) levels and decreases in the mean leukocyte count in the initial weeks following infliximab infusion, which returned to previous levels after 3 months.
Effect of 6-mercaptopurine on other medicinal products: Anticoagulants: Inhibition of the anticoagulant effect of warfarin and acenocoumarol has been reported when co-administered with 6-mercaptopurine; therefore higher doses of the anticoagulant may be needed. It is recommended that coagulation tests are closely monitored when anticoagulants are concurrently administered with 6-mercaptopurine.