What happens if you miss a dose of methotrexate?

Managing a Missed Dose of Methotrexate

If you miss a dose of methotrexate, do not double the next dose to make up for it. Instead, contact your healthcare provider for guidance on when to take your next dose.

Understanding Methotrexate Dosing

Methotrexate is typically administered as a once-weekly medication for conditions like rheumatoid arthritis and psoriasis, rather than daily like many other medications. This unique dosing schedule is critical to its safety profile:

• Methotrexate is usually given orally at doses ranging from 7.5 mg to 25 mg weekly as a single dose or divided into 3 doses over 24 hours 1
• The weekly dosing schedule is specifically designed to minimize toxicity while maintaining efficacy 1
• Dosage errors, particularly taking the medication more frequently than prescribed (e.g., daily instead of weekly), can lead to serious toxicity 2

Risks of Incorrect Dosing

Missing or incorrectly timing methotrexate doses can lead to several issues:

• Decreased efficacy if doses are consistently missed 1
• Potential serious toxicity if doses are taken too close together or if a "make-up" dose is taken 2
• Possible hematologic toxicity (bone marrow suppression) which can occur even after a single incorrectly timed dose 1

What To Do If You Miss a Dose

If you miss your scheduled methotrexate dose:

• Contact your healthcare provider as soon as possible for specific instructions 1
• Do not take a double dose to compensate for the missed dose 2
• Do not take the missed dose without consulting your provider, especially if it's close to your next scheduled dose 2

Monitoring After Missed or Delayed Doses

After a missed dose or dosing irregularity:

• Your healthcare provider may recommend additional monitoring of complete blood count (CBC), liver function tests (ALT/AST), and kidney function (creatinine) 1
• Watch for signs of toxicity including unusual fatigue, easy bruising, mouth sores, or fever 1
• Continue taking your prescribed folic acid supplement (at least 5 mg weekly) as this helps reduce potential side effects 1

Prevention of Dosing Errors

To avoid missing doses or taking incorrect doses:

• Use a medication calendar or set a weekly reminder 1
• Consider using a pill organizer specifically for your weekly methotrexate 1
• Ensure you understand the once-weekly dosing schedule and have this clearly marked on your prescription 1, 2
• Keep regular follow-up appointments for monitoring 1

Special Considerations

• If you're planning pregnancy, methotrexate should be stopped at least 3 months before conception for both men and women 1
• If you have decreased kidney function, even a single missed or incorrectly timed dose could lead to increased toxicity 1
• If you experience symptoms of toxicity after a missed or irregular dose, seek immediate medical attention 2

Remember that methotrexate is a powerful medication with significant benefits when taken correctly, but also potential serious side effects if dosing errors occur. Always consult your healthcare provider about any missed doses or concerns about your medication schedule.