Methotrexate Therapy Guidelines

Introduction to Methotrexate Therapy

Patients must be clearly informed that methotrexate is taken once weekly, not daily, to prevent potentially life-threatening toxicity, and should be provided with written information and a patient-held record book, as recommended by the British Journal of Dermatology 1
It is recommended to use only 25-mg tablets to avoid accidental overdose 1

Methotrexate is a teratogen that causes specific embryopathy, and women should not conceive while taking methotrexate or for at least 3 months after the last dose, and should use two methods of contraception throughout the treatment period 1
Men should delay planning a family for at least 3 months after the last dose 1
Pulmonary fibrosis is an absolute contraindication to methotrexate, and trimethoprim is also an absolute contraindication due to increased toxicity 1

Regular blood tests, including complete blood count, liver function tests, and renal function tests, are necessary throughout treatment, and patients must be able to comply with the monitoring schedule, as recommended by the British Journal of Dermatology 1
Monitoring of liver function is essential, and liver function tests (LFTs) should include ALT/AST, alkaline phosphatase, albumin, and bilirubin 1
The following laboratory tests are recommended for patients with rheumatoid arthritis:

Test	Frequency	Recommendation
CBC	Every 3-4 months	American Academy of Dermatology and American College of Rheumatology [2, 3, 4]
LFTs	Every 3-4 months	American Academy of Dermatology and American College of Rheumatology [2, 3, 4]
Renal function tests	Every 3-4 months	American Academy of Dermatology and American College of Rheumatology [2, 3, 4]

Blood tests should be performed at least 4-6 days after dosing to avoid detecting transient elevations in liver enzymes 5

Patients should limit alcohol intake well below national guidelines, and a pragmatic approach allowing occasional modest consumption may be reasonable for patients without additional hepatic risk factors, as recommended by the British Journal of Dermatology 1
Comorbidities such as metabolic syndrome components (dyslipidemia, hypertension, diabetes) should be managed in psoriasis patients with liver disease, as recommended by the American College of Rheumatology and the American Academy of Dermatology 2, 3, 4

NSAIDs can increase methotrexate toxicity, and antibiotics can also increase toxicity, as reported by the Journal of the American Academy of Dermatology 5
Concomitant use of certain medications, such as salicylates, probenecid, sulfonamides, phenytoin, tetracyclines, and chloramphenicol, should be avoided or monitored closely, as recommended by the Journal of the American Academy of Dermatology 6
Valproate increases the risk of hyperammonemia with topiramate, and monitoring of ammonia levels is recommended 6

Therapeutic effect typically takes 4-8 weeks to manifest, and maximum dose is typically 25 mg weekly, as recommended by the British Journal of Dermatology 1
Response is assessed after 3 months at maximum dose, and if ineffective, treatment may be discontinued or switched to subcutaneous formulation 1
Folic acid supplementation is strongly recommended for patients with rheumatoid arthritis, as recommended by the American Academy of Dermatology 2

Comprehensive laboratory testing, including complete blood count, liver function tests, renal function tests, hepatitis B and C screening, and tuberculosis screening, must be performed before starting methotrexate therapy, as recommended by the British Journal of Dermatology and the Journal of the American Academy of Dermatology 1, 4
Pregnancy testing before starting teratogenic medications and counseling on contraception methods are also recommended, as recommended by the American Academy of Dermatology 2
Obesity assessment should be performed, as BMI >30 increases hepatotoxicity risk, and diabetes status should be evaluated, as it increases hepatotoxicity risk, as recommended by the Journal of the American Academy of Dermatology 6

Failure to prescribe folic acid supplementation with methotrexate, which reduces adverse effects, as recommended by the British Journal of Dermatology 1
Confusing daily vs. weekly dosing, as methotrexate is typically given weekly, not daily, according to the British Journal of Dermatology 1
Overlooking renal function, as 85% of methotrexate is renally excreted, as stated by the British Journal of Dermatology 1
Ignoring drug interactions that may increase methotrexate toxicity, as recommended by the Journal of the American Academy of Dermatology 6
Missing early signs of toxicity, such as fever, mouth ulcers, unexplained bruising, and breathlessness, as recommended by the British Journal of Dermatology 1