MYTREX F
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MYTREX F (MYTREX F).
Methylprednisolone is a corticosteroid that inhibits phospholipase A2, reducing prostaglandin and leukotriene synthesis, and suppresses immune cell activity.
| Metabolism | Hepatic metabolism via CYP3A4, primarily to inactive metabolites. |
| Excretion | Renal: 90% unchanged; biliary/fecal: 10% as metabolites. |
| Half-life | 3.5 hours (terminal); prolonged to 8-12 hours in renal impairment. |
| Protein binding | 99% (primarily to albumin). |
| Volume of Distribution | 0.2 L/kg; indicates low tissue distribution, primarily in plasma. |
| Bioavailability | Oral: 80-90% (immediate-release); 70-80% (extended-release). |
| Onset of Action | Oral: 1-2 hours; IV: immediate (5-15 minutes). |
| Duration of Action | 4-6 hours; extended-release formulations up to 12 hours. |
| Molecular Weight | 454.44 Da |
Oral methotrexate 7.5-25 mg once weekly; subcutaneous methotrexate 7.5-25 mg once weekly; intravenous methotrexate 50-200 mg/m² every 2-3 weeks for oncology indications.
| Dosage form | CREAM |
| Renal impairment | GFR 60-90 mL/min: no adjustment; GFR 30-59 mL/min: reduce dose by 50%; GFR <30 mL/min: contraindicated (do not use). |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: contraindicated (do not use). |
| Pediatric use | For juvenile idiopathic arthritis: 10-15 mg/m² orally or subcutaneously once weekly; for leukemia: 15-30 mg/m² orally or intramuscularly once weekly. |
| Geriatric use | Initiate at lowest recommended adult dose due to reduced renal and hepatic function; monitor closely for toxicity; adjust based on renal function (see renal adjustment). |
| 1st trimester | Contraindicated: methotrexate is an abortifacient and teratogen; risk of skeletal and neural tube defects. |
| 2nd trimester | Contraindicated: continues to cause fetal abnormalities and growth restriction. |
| 3rd trimester | Contraindicated: risk of fetal toxicity, premature closure of ductus arteriosus, and neonatal effects. |
Clinical note
Comprehensive clinical and safety monograph for MYTREX F (MYTREX F).
| Placental transfer | Methotrexate crosses the placenta and accumulates in fetal tissues. |
| Breastfeeding | Methotrexate is excreted into breast milk in low concentrations, but due to potential for accumulation and toxicity in the nursing infant, the manufacturer recommends discontinuing nursing during therapy. |
| Lactation Rating |
■ FDA Black Box Warning
Corticosteroids may increase the risk of serious and potentially fatal infections. Live or live attenuated vaccines are contraindicated in patients receiving immunosuppressive doses of corticosteroids.
| Serious Effects |
PregnancyBreastfeedingSevere renal impairmentSevere hepatic impairmentPre-existing blood dyscrasiasActive infectionAlcoholismImmunodeficiency syndromes
| Precautions | Immunosuppression and increased risk of infections, Adrenal insufficiency with rapid withdrawal after prolonged therapy, Masking of signs of infection and new infections during use, Gastrointestinal perforation (especially in patients with IBD or diverticulitis), Osteoporosis with long-term use, Cushing's syndrome with prolonged therapy, Psychiatric disturbances (including depression, euphoria, psychosis), Kaposi's sarcoma has been reported in patients receiving corticosteroids, Exacerbation of systemic fungal infections; avoid in active untreated infections |
| Food/Dietary | No significant food interactions are reported; however, alcohol should be strictly avoided due to increased hepatotoxicity risk. Maintain adequate folate intake from diet or supplements. |
Loading safety data…
| L5 - Contraindicated |
| Teratogenic Risk | MYTREX F contains methotrexate, a known teratogen. First trimester: high risk of neural tube defects, craniofacial anomalies, and limb malformations (FDA Category X). Second and third trimesters: risk of fetal growth restriction, skeletal abnormalities, and neurodevelopmental delays. Contraindicated in pregnancy. |
| Fetal Monitoring | For inadvertent pregnancy exposure: serial fetal ultrasound for structural anomalies, detailed anatomy scan, and fetal echocardiography. Monitor maternal liver function, renal function, and complete blood count (CBC) weekly. Measure methotrexate levels if toxicity suspected. |
| Fertility Effects | Methotrexate can cause reversible oligospermia and menstrual dysfunction. Preclinical studies show impaired spermatogenesis and folliculogenesis. Contraceptive counseling is recommended for both males and females of reproductive potential. Effect on fertility may persist for several months after discontinuation. |
| Clinical Pearls | MYTREX F (methotrexate) is a folate analog antimetabolite used in rheumatoid arthritis, psoriasis, and certain malignancies. Monitor for hepatotoxicity, myelosuppression, and pulmonary toxicity. Administer folic acid to reduce side effects. Avoid NSAIDs as they can increase methotrexate levels. Use with caution in renal impairment. |
| Patient Advice | Take exactly as prescribed, usually once weekly for autoimmune conditions. · Avoid alcohol completely to reduce risk of liver damage. · Report any signs of infection, unusual bleeding, bruising, or shortness of breath. · Use effective contraception; methotrexate can cause fetal harm. · Do not take NSAIDs (ibuprofen, naproxen) without doctor approval. · Take folic acid as directed to minimize side effects. · Stay hydrated to help kidneys clear the drug. |