Home Drug Guide Methotrexate

Drug Guide

Generic Name

Methotrexate

Brand Names Otrexup, Otrexup Pfs, Rasuvo, Reditrex, Jylamvo

Classification

Therapeutic: Antineoplastic agent, Immunosuppressant

Pharmacological: Folate antagonist

FDA Approved Indications

  • Cancer (e.g., osteosarcoma, leukemias, lymphomas, breast cancer)
  • Rheumatoid arthritis
  • Psoriasis
  • Ectopic pregnancy (as part of medical management)

Mechanism of Action

Methotrexate inhibits dihydrofolate reductase, interfering with DNA synthesis, repair, and cellular replication, particularly affecting rapidly dividing cells.

Dosage and Administration

Adult: Dose varies based on condition; for rheumatoid arthritis, typically 7.5-20 mg once weekly; for cancer, doses are significantly higher and individualized.

Pediatric: Doses depend on the condition and weight; for leukemia, dose is based on body surface area.

Geriatric: Careful dose selection and monitoring due to increased risk of toxicity.

Renal Impairment: Reduce dose; consult specific guidelines.

Hepatic Impairment: Use with caution; liver function tests recommended before and during therapy.

Pharmacokinetics

Absorption: Variable; oral bioavailability approximately 50%.

Distribution: Widely distributed, crosses blood-brain barrier.

Metabolism: Minimal hepatic metabolism; small fraction undergoes hepatic conversion to active metabolites.

Excretion: Primarily renal excretion as unchanged drug.

Half Life: 3 to 10 hours; prolonged in renal impairment.

Contraindications

  • Pregnancy (category X), breastfeeding, liver disease, alcoholism, immunodeficiency, blood dyscrasias, renal impairment.

Precautions

  • Regular monitoring of CBC, liver and renal function; folic acid supplementation may be used to reduce toxicity; avoid in active infections.

Adverse Reactions - Common

  • Mucositis, nausea, vomiting (Frequent)
  • Myelosuppression (anemia, leukopenia, thrombocytopenia) (Frequent)
  • Liver toxicity (Frequent)

Adverse Reactions - Serious

  • Severe myelosuppression leading to bleeding or infection (Rare)
  • Liver fibrosis/cirrhosis (Rare)
  • Pneumonitis, pulmonary fibrosis (Rare)
  • Gastrointestinal perforation (Rare)

Drug-Drug Interactions

  • NSAIDs, penicillins, salicylates, antibiotics like trimethoprim, other hepatotoxic drugs

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Baseline CBC, liver and renal function tests; monitor for signs of infection, bleeding, hepatotoxicity.

Diagnoses:

  • Risk for infection
  • Imbalanced nutrition: less than body requirements
  • Impaired tissue integrity

Implementation: Administer as prescribed; ensure adequate hydration; educate patient about signs of toxicity.

Evaluation: Regular laboratory monitoring and clinical assessment for adverse effects.

Patient/Family Teaching

  • Take medication exactly as prescribed, once weekly, not daily.
  • Report signs of infection, bleeding, unusual fatigue.
  • Avoid alcohol and hepatotoxic drugs.
  • Use effective contraception during treatment and for at least 6 months after.

Special Considerations

Black Box Warnings:

  • Risk of severe and potentially fatal myelosuppression, hepatotoxicity, and tumor lysis syndrome.
  • Folic acid supplementation recommended to reduce some adverse effects.

Genetic Factors: Variants in drug metabolism pathways can affect toxicity.

Lab Test Interference: Can cause falsely elevated serum transaminases and bilirubin.

Overdose Management

Signs/Symptoms: Severe myelosuppression, mucositis, renal failure, hepatotoxicity, coma.

Treatment: Leucovorin (folinic acid) rescue therapy; gastric lavage; activated charcoal if early; supportive care in ICU.

Storage and Handling

Storage: Store at room temperature, away from light.

Stability: Stable for shelf-life specified by manufacturer.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.