Methotrexate is given weekly as an intramuscular injection of 15 to 25 mg. Side effects are rare and include leukopenia and hypersensitivity interstitial pneumonitis. Hepatic fibrosis is the most severe potential sequela of long-term therapy. Patients with concomitant alcohol abuse and/or morbid obesity are more likely to develop hepatic fibrosis and therefore should not be treated with methotrexate. It is prudent to obtain a baseline chest radiograph and to monitor complete blood count, liver function and renal function every two weeks until the patient is receiving oral therapy, and every one to three months thereafter. Before methotrexate therapy is initiated, the risks of treatment and the possible need for a liver biopsy should be discussed with the patient.