Purpose: A case of toxicity encountered with low-dose methotrexate therapy is discussed.
Summary: A 59-year-old African American woman receiving long-term therapy for psoriasis came to the hospital with painful ulcers, difficulty swallowing, cutaneous lesions, and acute renal failure. Her medical history included type 2 diabetes mellitus, hypertension, coronary artery disease, morbid obesity, and psoriasis. On admission, the patient looked ill and had a low-grade fever; maculopapular skin lesions; and bullae and vesicles in her mouth and on her hands, legs, groin, and buttocks. With the exception of carvedilol, all home medications, including methotrexate, were discontinued. A complete medication history revealed that the patient had been taking methotrexate 2.5 mg daily, instead of 2.5 mg three times weekly as prescribed. This error translated into an estimated cumulative dose of 360 mg, nearly twice the prescribed amount. There were no clinically significant drug-drug interactions noted among her prescribed medications; however, the patient did report increased ibuprofen use secondary to the painful ulcerations in the previous few months. Leucovorin 15 mg i.v. every six hours was initiated along with additional supportive care. Skin and mucosal lesions, as well as her pain, had dramatically improved on day 5 of hospitalization. The patient was discharged after a six-day hospitalization and was provided with leucovorin 15 mg orally ever day for seven additional days until rheumatology follow-up. The patient was instructed to avoid any future methotrexate therapy.
Conclusion: A patient who erroneously took oral methotrexate daily rather than thrice weekly for psoriasis developed multiple manifestations of methotrexate toxicity.