Methotrexate for Juvenile Idiopathic Arthritis

Serious but rare side effects of methotrexate include:

• Low blood counts.
• Inflammation of the lungs (allergic pneumonitis).
• Liver inflammation (abnormal liver enzyme blood tests or Reference hepatitis Opens New Window) or mild to moderate scarring (fibrosis). Liver inflammation or fibrosis seems to be less common and less severe in children than in adults.
• Severe liver damage (severe scarring or Reference cirrhosis Opens New Window). Cirrhosis is not reversible, but it is rare and is most often seen in patients with liver disease, diabetes, or alcohol abuse.

Minor side effects include:

• Stomach and intestinal symptoms (nausea, vomiting, diarrhea, or stomach upset). If your child becomes severely Reference dehydrated Opens New Window from vomiting or diarrhea, methotrexate should be stopped until the symptoms go away.
• Mouth sores.
• Hair thinning.

None of these side effects are permanent. Reference Folic acid Opens New Window supplements may decrease the severity of side effects.

Effects on blood cells and liver inflammation can be detected early by regular blood tests (every 1 to 2 months) and almost always return to normal when methotrexate is discontinued. Regular blood tests may help detect liver inflammation. In very rare cases, inflammation can lead to more serious liver scarring (fibrosis or cirrhosis).

Anyone taking methotrexate must avoid alcohol use to prevent significant drug interactions.

Women taking methotrexate should avoid becoming pregnant, as the drug causes miscarriage and possibly birth defects.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

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