MYTREX F

Clinical safety rating: caution

Comprehensive clinical and safety monograph for MYTREX F (MYTREX F).

How it works

Methylprednisolone is a corticosteroid that inhibits phospholipase A2, reducing prostaglandin and leukotriene synthesis, and suppresses immune cell activity.

What the body does with it

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.

Classification & Brands

Dosing & administration

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).

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for MYTREX F (MYTREX F).

Breastfeeding	Methotrexate is excreted into breast milk in low concentrations; M/P ratio approximately 0.08. Due to potential for accumulation and adverse effects (bone marrow suppression, gastrointestinal toxicity) in the neonate, breastfeeding is contraindicated during MYTREX F therapy.
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.

Warnings & precautions

■ 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.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Systemic fungal infections (except when used for specific indications)","Hypersensitivity to methylprednisolone or any component","Live or live attenuated vaccines (in immunosuppressive doses)","Idiopathic thrombocytopenic purpura (intramuscular use only)"]

Clinical Precautions

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"]

Clinical Tips & Counseling

Drug interactions

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MYTREX F

Clinical safety rating: caution

Comprehensive clinical and safety monograph for MYTREX F (MYTREX F).

How it works

Methylprednisolone is a corticosteroid that inhibits phospholipase A2, reducing prostaglandin and leukotriene synthesis, and suppresses immune cell activity.

What the body does with it

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.

Classification & Brands

Dosing & administration

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).

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for MYTREX F (MYTREX F).

Breastfeeding	Methotrexate is excreted into breast milk in low concentrations; M/P ratio approximately 0.08. Due to potential for accumulation and adverse effects (bone marrow suppression, gastrointestinal toxicity) in the neonate, breastfeeding is contraindicated during MYTREX F therapy.
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.