Methotrexate Weekly Dosage
For rheumatoid arthritis, oral methotrexate should be started at 10-15 mg/week with escalation of 5 mg every 2-4 weeks up to 20-30 mg/week, depending on clinical response and tolerability. 1
Starting Dose by Indication
Rheumatoid Arthritis
- Initial dose: 10-15 mg/week orally 1
- The 2021 ACR guidelines conditionally recommend titration to at least 15 mg/week within 4-6 weeks to optimize efficacy 1
- Starting at 15 mg weekly is reasonable in patients with normal renal function, reserving lower starting doses (2.5-5 mg test dose) for those with increased risk factors (renal impairment, elderly, drug interactions) 1
Psoriasis
- Typical dosing range: 7.5-25 mg weekly 1
- Can be given as a single dose or divided into 3 doses over 24 hours 1
- NICE recommends starting at 5-10 mg once weekly with gradual increases up to a maximum of 25 mg weekly 1
- More aggressive regimens may start at 15 mg weekly in appropriate patients 1
Dose Escalation Strategy
Increase by 5 mg every 2-4 weeks based on clinical response and tolerability, targeting 20-30 mg/week for rheumatoid arthritis 1. Evidence shows:
- Rapid escalation (5 mg/month to 25-30 mg/week) achieves higher efficacy but with more adverse events compared to slow escalation (5 mg every 3 months) 1
- Starting at 25 mg/week is more effective than 15 mg/week but trends toward more gastrointestinal toxicity 1
- For psoriasis, dose adjustments may take at least 4 weeks for clinical response 1
Maximum Dose Considerations
- Standard maximum: 25 mg/week for both rheumatoid arthritis and psoriasis 1
- Some guidelines allow up to 30 mg/week for rheumatoid arthritis in selected cases 1
- Doses >20 mg/week significantly increase risk of serious toxicity, particularly bone marrow suppression 2
- For pediatric JRA, limited data exists for doses 20-30 mg/m²/week, though better absorption and fewer GI side effects occur with parenteral administration at these higher doses 2
Route of Administration
Oral administration is preferred initially, but parenteral (subcutaneous or intramuscular) should be considered for: 1
- Inadequate clinical response to oral therapy
- Gastrointestinal intolerance
- Poor compliance
- Doses >20 mg/week (due to bioavailability concerns)
The 2021 ACR guidelines conditionally recommend switching to subcutaneous methotrexate over adding/switching to alternative DMARDs when oral methotrexate fails to achieve target 1. Parenteral administration offers higher bioavailability and may reduce GI toxicity 1.
Essential Folic Acid Supplementation
At least 5 mg folic acid per week is strongly recommended with methotrexate therapy 1. Specific regimens include:
- Daily dosing except on methotrexate day to avoid interfering with efficacy 1
- Reduces hepatic abnormalities and GI adverse effects 1
- No proven difference between folic acid and folinic acid, but folic acid is less expensive 1
- Large doses may reduce methotrexate efficacy 1
Critical Monitoring Requirements
Before initiating therapy, obtain: 1
- CBC, AST/ALT, albumin, creatinine
- Chest X-ray (within previous year)
- Consider hepatitis B/C serology, HIV, fasting glucose, lipid profile, pregnancy test
During therapy: 1
- CBC, liver function tests, creatinine every 1-1.5 months until stable dose achieved
- Then every 1-3 months thereafter
- For psoriasis, monitoring every 3-6 months is acceptable once stable 1
Common Pitfalls to Avoid
- Never use preserved formulations for intrathecal or high-dose therapy (contains benzyl alcohol) 2
- Methotrexate is dosed WEEKLY, not daily - dosing errors are a major cause of toxicity 1
- Stop if ALT/AST >3× upper limit of normal (confirmed) 1
- Contraindicated in pregnancy - discontinue at least 3 months before planned conception for both men and women 1
- Watch for drug interactions, particularly NSAIDs, proton pump inhibitors, and DPP-4 inhibitors which can delay elimination 3