Background and Importance Methotrexate (MTX) is a cytostatic drug used as an immunomodulator in non-oncological diseases, dosed at 7–25 mg per week orally/subcutaneously in adults. It is catalogued by the ISMP (Institute for Safe Medication Practices) as ‘high-risk drugs’, which incorrectly used have a higher likelihood of causing serious-fatal harm to patients. Folic acid (FA) is administered to prevent MTX toxicity.

Aim and Objectives To analyse pharmaceutical interventions (PIs) on oral/subcutaneous MTX and FA prescriptions and to assess the acceptance degree by the physicians.

Material and Methods Prospective observational study.

Oral/subcutaneous MTX prescriptions in adults between March to May 2023 of patients in a third-level hospital area were obtained. Filters applied to detect errors were: dosage of one tablet (2.5 mg) and administration frequency different from 7 days. Once patients were identified, MTX and FA prescriptions were reviewed and the responsible physician was contacted. The acceptance degree of the PIs was measured.

The following variables were collected: number of patients on whom PIs were performed, sex, age, diagnosis, number and type of PIs identified.

Results Thirty-six patients with erroneous prescriptions were detected. 67% were female. The median age was 54 years (18–86).

The associated pathologies were included in the rheumatologic (n=23, 63.9%), dermatologic (n=8, 22.2%), and internal medicine (n=5, 13.9%) areas: rheumatologic arthritis (n=8, 22.2%), juvenile idiopathic arthritis (n=3,8.3%), psoriatic spondyloarthritis (n=4, 11.1%), polyarthritis (n=1, 2.8%), psoriasis (n=6, 16.7%) and others (n=14, 38.9%).

Of all the PIs performed (n=53), the pharmacist recommended adjustment of: MTX dosage (n=11), MTX administration frequency (n=30), FA administration frequency (n= 9) and lack of FA prescription (n=3).

The acceptance degree of the PIs were as follows: MTX dosage (45.5%), MTX administration frequency (80.0%), FA administration frequency (55.6%) and lack of FA prescription (66.7%).

Conclusion and Relevance Most of the PIs were about errors in prescribing the MTX administration frequency, daily instead of weekly, implying a high risk of intoxication. The acceptance degree of the PIs was very high, reinforcing the role of the pharmacist.

Conflict of Interest No conflict of interest.