Thiocolchicoside and Methotrexate Interaction

Mechanism of Concern

Colchicine is specifically listed as a drug that increases methotrexate toxicity through decreased renal tubular excretion, leading to reduced renal elimination and increased serum methotrexate levels, according to the American Academy of Dermatology 1, 2
The interaction occurs because colchicine decreases methotrexate binding to serum albumin and impairs renal tubular secretion, resulting in methotrexate accumulation, as reported by the American Academy of Dermatology 2

Both drugs are hepatotoxic, and concurrent use would require more frequent liver function monitoring, as recommended by the American Academy of Dermatology 1, 2
Methotrexate hepatotoxicity is well-established, particularly in psoriasis patients, according to the American Academy of Dermatology 3

Renal insufficiency significantly increases the danger of combining these medications, as methotrexate is 85% renally excreted, and impaired clearance dramatically increases toxicity risk, as reported by the American Academy of Dermatology 1
Hypoalbuminemia reduces methotrexate protein binding, increasing free drug levels, according to the American Academy of Dermatology 3

Increase monitoring frequency to every 2-4 weeks initially, checking CBC with differential, liver function tests, and renal function, as recommended by the American Academy of Dermatology 4, 5
Ensure folic acid supplementation at 1-5 mg daily except on methotrexate dosing day, as recommended by the American Academy of Dermatology 6
Consider reducing methotrexate dose to minimize cumulative toxicity risk, as suggested by the American Academy of Dermatology 1

Patients must be educated to report immediately symptoms such as fever or flu-like illness, mouth ulceration, unusual bruising or bleeding of gums, severe nausea, vomiting, or abdominal pain, dark urine, or breathlessness or cough, as recommended by the British Journal of Dermatology and the American Academy of Dermatology 6, 7, 3