Common Administration Routes for Methotrexate
Methotrexate is typically given orally as tablets for low-dose weekly regimens in rheumatoid arthritis or psoriasis, with doses starting at 7.5-15 mg once a week.[1] For higher doses or faster absorption—such as in acute lymphoblastic leukemia or when oral tolerance is poor—it's administered via subcutaneous injection using prefilled syringes or auto-injectors, often self-administered at home.[1][2]
Intramuscular or intravenous injections are standard for oncology uses, where doses exceed 100 mg/m² and require hospital monitoring to manage toxicity.[1]
Oral vs. Injectable: When Doctors Choose Each
Oral methotrexate has nearly 100% bioavailability at low doses but drops to 60-80% at higher ones due to first-pass metabolism, prompting switches to injections.[2] Subcutaneous routes match oral efficacy for autoimmune conditions while reducing nausea, making them preferred for long-term use.[1][2] Intrathecal injection directly into the spinal canal treats central nervous system involvement in leukemia.[1]
Dosing Schedules and Frequency
Weekly dosing is standard for non-cancer uses to minimize side effects like liver toxicity; daily high-dose IV is reserved for cancer protocols with leucovorin rescue.[1] Patients often start low and titrate up based on blood tests monitoring folate levels and organ function.[2]
Self-Administration Options for Patients
Prefilled syringes (e.g., Otrexup, Rasuvo) allow weekly home injections with doses from 7.5-25 mg, including features like auto-retracting needles for safety.[1] Oral tablets remain first-line for ease, but injections suit those with gastrointestinal issues.[2]
What Happens with Missed Doses or Overdose Risks
Skip a missed low-dose without doubling up; consult a doctor immediately for high-dose regimens due to rapid toxicity buildup affecting bone marrow and mucosa.[1] Folic acid supplements are routinely prescribed to counter side effects across all routes.[2]
[1]: MedlinePlus - Methotrexate
[2]: Drugs.com - Methotrexate