Methotrexate

Methotrexate: Comprehensive Patient Information (Australia)

Basic Product Information

Mechanism of Action

Methotrexate is a medicine used to treat certain cancers, autoimmune diseases (such as rheumatoid arthritis and psoriasis), and other inflammatory conditions. It works by slowing or stopping the growth of cells in your body—especially those that cause inflammation or divide rapidly, like cancer cells.

Methotrexate is a folate antimetabolite. It inhibits the enzyme dihydrofolate reductase (DHFR), impeding DNA synthesis, repair, and cellular replication. This suppression is particularly pronounced in actively proliferating cells, such as malignant cells, immune cells in autoimmune disease, and rapidly dividing epithelial tissues. At lower doses, it has anti-inflammatory and immunosuppressive effects, influencing purine metabolism, increasing adenosine release, and suppressing T-cell activation.

Pharmacokinetics

• Absorption: After oral administration, methotrexate is variably absorbed, with bioavailability ranging from 60-70% at low doses (<30 mg/m²); higher doses decrease absorption efficiency due to a saturable uptake mechanism.
• Distribution: Widely distributed in body tissues and fluids; limited penetration into the CNS unless given in high doses or intrathecally.
• Metabolism: Partially metabolised in the liver; the active metabolite polyglutamated methotrexate accumulates in cells.
• Elimination: Excreted primarily via the kidneys (renal route); t_1/2 = 3–10 hours (longer in high doses, renal impairment, or accumulation).
• Duration of Action: Weekly doses for autoimmune diseases persist for 5–7 days; cancer protocol dosing may be daily or more frequent.

Use in Everyday Life and Best Practices

Methotrexate is commonly prescribed by specialist doctors and dispensed by your pharmacist. The most frequent uses in Australia include:

• Rheumatoid Arthritis – reducing joint inflammation and pain
• Psoriasis – controlling flares and thickening of the skin
• Certain Cancers (e.g., lymphoma, leukaemia, breast cancer)
• Crohn’s Disease and other off-label uses

• Never take methotrexate every day unless explicitly instructed by your specialist. Weekly dosing is standard for inflammatory diseases.
• Folic acid supplementation (usually 5 mg once weekly, on a different day to methotrexate) is frequently prescribed alongside methotrexate to reduce side effects.
• Regular blood monitoring (full blood count, liver, and kidney function) is essential to ensure safety. Your GP or rheumatologist will set up these tests for you.

Dosing in the Morning vs Evening

• Dosing at the same time each week is more important than the choice of morning or evening.
• Some patients report less nausea when taking methotrexate in the evening after food, while others prefer mornings.
• Choose a time that helps you remember your dose consistently—your pharmacist can provide medication planners for this purpose.
• Avoid taking methotrexate just before bedtime if you are prone to stomach upset.

Taking Methotrexate with Food or on an Empty Stomach

You may take methotrexate tablets with or without food. In Australia, typical dietary habits (three meals a day with varied intake) do not significantly interfere with methotrexate absorption at normal doses. For some, taking it with food may help reduce gastric upset or nausea. However, high-fat meals might slightly lower absorption—if you experience gastrointestinal discomfort, discuss possible dose timing with your doctor or pharmacist.

Interaction Warnings

Indications for Methotrexate

Dosing According to Clinical Indication

Safety Profile and Possible Side Effects

• Pregnancy and breastfeeding: Methotrexate is contraindicated—discuss reliable contraception with your doctor.
• Older adults: May be more susceptible to side effects—lower doses and extra monitoring recommended.

Guidelines for Proper Use (Australia Context)

• Always follow your specialist’s instructions exactly; do not change your dose or frequency without medical advice.
• Use pharmacy-supplied reminder cards or apps to track weekly dosing and avoid accidental overdoses.
• Maintain regular blood test appointments as scheduled by your GP or hospital clinic.
• Report any unusual symptoms (mouth ulcers, unexplained bruising, yellowing of the skin, cough, breathlessness) promptly to your healthcare provider.
• Keep the medicine out of reach of children; store at room temperature, protected from light and moisture.
• If you miss a dose, take it as soon as you remember within 48 hours; otherwise, skip and resume your regular schedule. Do not double up the next dose.
• Do not share your methotrexate with anyone, even if they have similar symptoms.

Alternative Treatment Options

• Leflunomide – another DMARD, similar efficacy in RA, may be used if methotrexate is not tolerated; can cause diarrhoea and liver abnormalities.
• Biologics (e.g. adalimumab, etanercept, infliximab) – effective, especially when methotrexate fails or is not tolerated; higher cost, increased infection risk, usually reserved for hospital initiation.
• Sulfasalazine – can be used alone or with methotrexate for inflammatory arthritis.
• Hydroxychloroquine – mild DMARD, fewer side effects but less potent.

Pros of Methotrexate: Long track record, cost-effective, covered by the PBS for most indications.
Cons: Weekly dosing complexity, need for blood monitoring, risk of rare but serious side effects.

Legal, Registration, and Reimbursement Status in Australia

• Methotrexate is fully registered with the Therapeutic Goods Administration (TGA).
• It is listed on the Pharmaceutical Benefits Scheme (PBS) for approved indications, ensuring subsidised access for eligible patients.
• Prescription is required; only a registered medical practitioner may initiate therapy.
• Dispensing is controlled under Schedule 4 (Prescription Only Medicine).
• Strict monitoring and documentation requirements apply due to its special risk profile.

Latest Research and Clinical Guidance (2022–2025)

• 2023: Updates to Australian Rheumatology Association (ARA) guidelines reaffirm methotrexate as first-line therapy in rheumatoid arthritis and recommend ongoing cardiovascular monitoring due to small increased risk (Source: ARA Guidelines 2023).
• 2024: International consensus reports support low-dose methotrexate for psoriasis with individualized monitoring for liver and lung complications (Lancet Rheumatology, 2024).
• Trials are ongoing for methotrexate in combination with biologic or JAK inhibitors for refractory inflammatory arthritis.
• Recent studies highlight the importance of strict adherence to weekly dosing to reduce risk of toxicity (BMJ, 2022).

Availability, Packs and Delivery in Australia

Frequently Asked Questions (FAQ)

1. How long does methotrexate take to work for arthritis or psoriasis?
   Most people notice improvement after 3–6 weeks, with maximum benefit at 3–6 months. Blood tests and regular reviews help your doctor assess response and side effects.
2. Can I drink alcohol while taking methotrexate?
   It is best to avoid alcohol or keep it to a minimum, as both methotrexate and alcohol can cause liver damage. Discuss safe limits with your GP.
3. What should I do if I accidentally take my methotrexate dose more than once a week?
   Contact your doctor or Poisons Information Centre (13 11 26) immediately—even if you feel fine, as overdose can cause serious harm.
4. Is it safe during pregnancy and breastfeeding?
   No—methotrexate can cause serious birth defects and must not be used during pregnancy or breastfeeding. Reliable contraception is essential for both women and men using methotrexate.
5. Do I need special precautions if I become unwell or require surgery?
   Inform all healthcare professionals (including your surgeon or dentist) you are taking methotrexate; you may need to pause treatment if you have an infection or undergo major procedures.

Please discuss any concerns or specific situations with your healthcare provider or consult your pharmacist before making changes to your medication routine.