Metotrexato Semanal Orion Pharma (Methotrexate)

Methotrexate is employed across several disease families, primarily as an immunosuppressive and anti‑proliferative agent.

• Rheumatoid arthritis: reduces joint inflammation and slows structural damage.
• Psoriasis: decreases skin cell proliferation and improves plaque lesions.
• Leukemia: interferes with malignant cell DNA synthesis, aiding remission.
• Lymphoma: limits growth of malignant lymphocytes and supports combination chemotherapy regimens.

• Methotrexate inhibits dihydrofolate reductase, blocking tetrahydrofolate production and thereby reducing purine and pyrimidine synthesis. This leads to impaired DNA replication and cell division, particularly affecting rapidly proliferating immune cells and malignant cells, resulting in immunosuppression and anti‑cancer activity.

Methotrexate may cause a range of adverse reactions that vary in frequency and severity.

Common Side Effects

• Nausea or vomiting: mild to moderate gastrointestinal upset.
• Fatigue: persistent tiredness unrelated to activity level.
• Oral ulcers: painful sores in the mouth.
• Elevated liver enzymes: mild hepatic irritation.
• Decreased blood counts: mild anemia or leukopenia.
• Hair thinning: temporary reduction in scalp hair density.

Serious or Rare Side Effects

• Severe liver toxicity: risk of hepatitis or fibrosis.
• Pulmonary fibrosis: progressive lung scarring.
• Bone marrow aplasia: profound pancytopenia.
• Renal failure: impaired kidney function.
• Severe skin reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Opportunistic infections: due to marked immunosuppression.

Before initiating therapy, clinicians should evaluate baseline health status and monitor key parameters throughout treatment.

• Liver monitoring: perform baseline and periodic liver function tests.
• Hematologic monitoring: check complete blood counts regularly.
• Pregnancy avoidance: methotrexate is contraindicated; ensure effective contraception.
• Renal function: assess creatinine clearance and adjust dose if needed.
• Drug interactions: review concomitant medications for additive toxicity.
• Store at ambient temperature: keep in the original container, protect from moisture and direct sunlight.

Methotrexate interacts with several medicines that can alter its safety or efficacy.

Major Interactions (Avoid)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs): increase risk of renal toxicity and gastrointestinal ulceration.
• Trimethoprim‑sulfamethoxazole: potentiates bone‑marrow suppression.
• Live vaccines: may cause uncontrolled infection due to immunosuppression.

Moderate Interactions (Monitor Closely)

• Proton‑pump inhibitors: may affect methotrexate clearance, requiring dose review.
• Alcohol: can exacerbate hepatic toxicity.
• Penicillins and sulfonamides: may increase hematologic adverse effects.