Metoject (Methotrexate)

Methotrexate is used to modulate immune activity and cell proliferation in several disease categories.

• Rheumatoid arthritis: reduces synovial inflammation, alleviates pain, and slows radiographic joint damage in adult patients.
• Severe plaque psoriasis: decreases keratinocyte proliferation, leading to reduction of plaque thickness and scaling.
• Acute lymphoblastic leukemia and osteosarcoma: impedes DNA synthesis in rapidly dividing malignant cells, contributing to remission.
• Juvenile idiopathic arthritis: moderates systemic and joint inflammation, improving functional outcomes in children.

• Methotrexate acts as a folate antagonist by competitively inhibiting dihydrofolate reductase, which blocks the conversion of dihydrofolate to tetrahydrofolate. This inhibition reduces the availability of reduced folate cofactors required for thymidylate and purine synthesis, thereby impairing DNA replication and cell division. The resulting antiproliferative effect is most pronounced in rapidly dividing immune cells and malignant cells. Additionally, methotrexate promotes accumulation of adenosine, which contributes to its anti‑inflammatory properties.

Methotrexate may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Fatigue: persistent tiredness.
• Oral ulcers: painful sores in the mouth.
• Elevated liver enzymes: mild hepatic irritation.
• Low blood counts: mild leukopenia or anemia.
• Diarrhea: loose stools.
• Headache: mild to moderate.

Serious or Rare Side Effects

• Severe hepatotoxicity: potential liver fibrosis or cirrhosis.
• Pulmonary toxicity: interstitial pneumonitis or fibrosis.
• Bone marrow suppression: profound pancytopenia.
• Renal impairment: acute kidney injury.
• Severe cutaneous reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Severe infection: opportunistic infections due to immunosuppression.

When using methotrexate, several precautions should be observed to minimize risks.

• Baseline testing: obtain liver function, renal function, and complete blood count before initiation.
• Monitoring: perform regular laboratory assessments to detect hepatotoxicity or marrow suppression.
• Pregnancy: avoid use in pregnancy due to teratogenic risk; effective contraception is required.
• Drug interactions: review concomitant medications for potential additive toxicity.
• Patient education: inform about signs of infection, liver dysfunction, and pulmonary symptoms.
• Store at ambient temperature: keep in original container, protect from moisture and light.

Methotrexate interacts with several medicines, influencing its efficacy and safety profile.

Major Interactions (Avoid)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs): increase risk of renal toxicity.
• Proton pump inhibitors (e.g., omeprazole): may elevate methotrexate levels and toxicity.
• Trimethoprim‑sulfamethoxazole: potentiates bone marrow suppression.

Moderate Interactions (Monitor Closely)

• Live vaccines: immunosuppression may reduce vaccine efficacy and increase infection risk.
• Azathioprine or other immunosuppressants: additive myelosuppression.
• Alcohol: can exacerbate hepatotoxicity.