Increased risk of methotrexate intoxication in the elderly
INTRODUCTION
Over two decades, low dose methotrexate (MTX) has been used as a therapy for rheumatoid arthritis and psoriasis [1,2]. The biggest risk of MTX therapy is the development of toxicity with associated side effects and ultimately mortality. Low dose methotrexate use in elderly patients more often leads to MTX intoxication with serious consequences. For atypical complaints in frail older people using methotrexate, the MTX intoxication should be in the differential diagnosis. In this article we describe a patient presenting with atypical complaints as a result of an MTX intoxication.
DESCRIPTION
A 76-year-old female presents with severe dyspnea, during rehabilitation therapy of a recently experienced stroke. She has heart failure NYHA class II and rheumatoid arthritis. She is treated with a low dose schedule of methotrexate, 10 mg per week combined with folic acid 5 mg three times per week and hydroxychloroquine (Plaquenil) 200 mg once daily.
Additional laboratory tests show abnormal values including increased liver values, impaired renal function and bone marrow suppression. Because of known MTX use in combination with the laboratory abnormalities found with unclear underlying cause, an MTX blood level is determined. This appears to be largely increased. Calcium folinate is started intravenously, despite improving blood results the patient does not improve and a palliative policy is followed.
DISCUSSION
For atypical complaints in frail older people using methotrexate, the MTX intoxication should be in the differential diagnosis. Measuring methotrexate levels is unusual in Dutch rheumatology, partly due to the short half-life of MTX. Literature study shows several cases in which inadequate intake of MTX – as well as adequate intake – leads to an MTX intoxication. Decreased kidney function leads to an increased risk of MTX intoxication. Therefore it is, especially in elderly patients with MTX therapy, advisable to frequently check renal function. Dose adjustment should be made in case of impaired renal function and measurement of MTX levels should be considered. Elderly presenting atypical complaints is a common sight. Doctors should ensure that MTX therapy is adequately followed and MTX intoxication must be in the differential diagnosis in elderly with atypical complaint presentation.
CONCLUSION
The risk of developing MTX intoxication in frail elderly is increased despite prescription MTX use. In this category of patients, this often leads to an atypical complaint presentation. For atypical complaints in frail older people using methotrexate, the MTX intoxication should be in the differential diagnosis. Especially with a reduced kidney function, the risk of an MTX-intoxication is higher. In addition, with MTX use the dose regime and actual intake must be extensively requested to prevent fatal consequences.