Metex (Methotrexate)

• Methotrexate is a folate antagonist used across several disease families.
• Rheumatoid arthritis: reduces joint inflammation and slows structural damage.
• Psoriasis: limits skin cell proliferation and improves plaque lesions.
• Acute lymphoblastic leukemia and non‑Hodgkin lymphoma: interferes with malignant cell replication.
• Ectopic pregnancy: medically terminates non‑viable implantation when surgery is not indicated.

• Methotrexate inhibits dihydrofolate reductase, preventing the conversion of dihydrofolate to tetrahydrofolate. This blockade reduces purine and pyrimidine synthesis, impairing DNA, RNA and protein production, which limits the proliferation of rapidly dividing cells such as immune cells and cancer cells.

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

Common Side Effects

• Nausea or vomiting
• Fatigue or malaise
• Oral mucosal ulceration
• Mild elevation of liver enzymes
• Transient low white‑blood‑cell count
• Temporary hair thinning

Serious or Rare Side Effects

• Severe hepatotoxicity or fibrosis
• Pulmonary fibrosis or interstitial pneumonitis
• Life‑threatening bone‑marrow suppression
• Acute renal failure
• Stevens‑Johnson syndrome or toxic epidermal necrolysis
• Opportunistic infections due to immunosuppression

• When using methotrexate, several safety considerations should be observed.
• Pregnancy: contraindicated (Category X) – avoid use in women of childbearing potential without effective contraception.
• Renal function: assess baseline creatinine and adjust dose in impairment.
• Liver function: monitor transaminases regularly; avoid in pre‑existing severe hepatic disease.
• Hematologic monitoring: perform complete blood counts before each dose to detect cytopenias.
• Alcohol consumption: limit or avoid to reduce additional liver injury.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Methotrexate interacts with several medicines that may increase toxicity or reduce efficacy.

Major Interactions (Avoid)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs) – increase methotrexate serum levels.
• Proton‑pump inhibitors (e.g., omeprazole) – may raise toxicity.
• Trimethoprim‑sulfamethoxazole – additive bone‑marrow suppression.
• Live vaccines – risk of infection due to immunosuppression.
• Gold salts – synergistic toxicity.

Moderate Interactions (Monitor Closely)

• Azathioprine or cyclosporine – combined immunosuppression.
• Penicillins (high‑dose) – possible reduced clearance.
• Sulfonamide antibiotics – overlapping hematologic effects.
• Folic acid supplements – may lessen efficacy if not properly timed.
• Vitamin B12 – monitor for additive hematologic changes.