(1997; 24 pages)
Methotrexate (low-dose) - blood dyscrasias and other adverse reactions: United Kingdom
United Kingdom. The Committee on Safety of Medicines has alerted prescribers to reports of blood dyscrasias and other adverse reactions associated with the use of low-dose methotrexate. Methotrexate is an antimetabolite which is used at high doses to treat neoplastic diseases and, at lower doses, to treat psoriasis and rheumatoid arthritis.
At high doses, methotrexate is well known to be associated with serious and sometimes fatal blood dyscrasias, and less often with hepatitis, cirrhosis and pulmonary fibrosis. The Committee has received 83 reports of blood dyscrasias, 36 with fatal outcome, in patients receiving low-dose methotrexate. In many of these cases there were factors which were likely to have increased the toxicity of methotrexate including advanced age, impaired renal function and interactions with drugs with anti-folate properties (e.g. trimethoprim/sulfamethoxazole). A further 4 reports have been received of liver cirrhosis associated with low-dose methotrexate treatment for psoriasis or rheumatoid arthritis.
The Committee stresses that patients receiving low-dose methotrexate should:
. have a full blood count as well as renal and liver function tests before starting treatment. These should be repeated weekly until therapy is stabilized, thereafter patients should be monitored every 2-3 months throughout treatment.
. report all symptoms and signs suggestive of infection, especially sore throat.
If acute methotrexate toxicity occurs, patients may require treatment with folinic acid.
[See also Pharmaceuticals Newsletter No. 10, October 1995]
Reference: Current Problems in Pharmacovigilance Vol. 23, September 1997.