Injexate (Methotrexate)

Methotrexate is used in several autoimmune and oncologic disease pathways.

• Rheumatoid arthritis: reduces joint inflammation and slows structural damage.
• Psoriasis: improves skin lesions and decreases disease severity.
• Acute lymphoblastic leukemia: contributes to remission by inhibiting malignant cell proliferation.
• Non‑Hodgkin lymphoma: used as part of combination regimens to achieve tumor control.

• Methotrexate inhibits dihydrofolate reductase, blocking the conversion of dihydrofolate to tetrahydrofolate, a cofactor required for purine and pyrimidine synthesis. This disruption reduces DNA, RNA and protein production, limiting the proliferation of rapidly dividing cells such as activated lymphocytes and cancer cells. The drug also promotes the release of adenosine, which exerts anti‑inflammatory effects on immune pathways. Consequently, methotrexate modulates immune response and impairs tumor growth.

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

Common Side Effects

• Nausea or vomiting: gastrointestinal upset occurring early in therapy.
• Fatigue: general tiredness or reduced energy.
• Mouth sores: ulceration of oral mucosa.
• Elevated liver enzymes: mild hepatic irritation.
• Low blood cell counts: mild leukopenia or anemia.

Serious or Rare Side Effects

• Severe liver toxicity: potential for hepatitis or fibrosis.
• Pulmonary fibrosis: interstitial lung disease with breathing difficulty.
• Bone marrow suppression: profound pancytopenia.
• Renal impairment: acute kidney injury from drug accumulation.

Before initiating methotrexate therapy, several safety considerations should be reviewed.

• Pregnancy: contraindicated (Category X); avoid use in pregnant or planning patients.
• Renal function: assess creatinine clearance and adjust if impaired.
• Liver function: perform baseline transaminases and monitor regularly.
• Hematologic status: obtain complete blood count prior to start and during treatment.
• Concomitant vaccines: avoid live vaccines while on therapy.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze.

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

Major Interactions (Avoid)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs): may increase methotrexate serum levels and risk renal toxicity.
• Proton pump inhibitors (e.g., omeprazole): can reduce renal clearance and raise drug exposure.
• Trimethoprim‑sulfamethoxazole: potentiates bone marrow suppression.

Moderate Interactions (Monitor Closely)

• Azathioprine or mycophenolate: additive immunosuppression may increase infection risk.
• Live vaccines: may cause severe infection due to immunosuppression.
• Alcohol: can exacerbate hepatic toxicity.