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Beware of erroneous daily oral methotrexate dosing



From the April 3, 2002 issue


PROBLEM: The perils of low-dose oral methotrexate are clearly evident in the dozens of fatalities reported in patients who have been prescribed this cytotoxic agent for alternative conditions. While methotrexate has a well-established role in oncology, increasingly it's being used in low doses for immunomodulation in rheumatoid arthritis, asthma, psoriasis, inflammatory bowel disease, myasthenia gravis, and inflammatory myositis. Used for these purposes, it's administered as a weekly dose. But mistakes have been all too frequent because relatively few medications are dosed in this manner and clinicians and patients are much more familiar with daily dosing of medications. For example, one patient died after he misunderstand the directions for use and took methotrexate 2.5 mg every 12 hours for six consecutive days, instead of 2.5 mg every 12 hours for three doses each week. Another patient died after he misread the directions on a prescription bottle and took 10 mg every "morning" instead of every "Monday." Errors also have been reported with hospitalized patients. In one case, the physician had properly recorded that the patient had been taking methotrexate 7.5 mg weekly as an outpatient. But when he prescribed three 2.5 mg tablets weekly, it was transcribed incorrectly as three times daily. Upon transfer to another unit, the dose was transcribed incorrectly as three times a week. In each case the errors did not reach the patient because they were detected during pharmacy review of the order. Similar errors have been reported overseas. For example, in Australia, one patient took extra doses of methotrexate as needed to relieve arthritic symptoms. Three elderly patients took the medication daily despite clearly written instructions to take it weekly. Two cases involved incorrect transcription of the dosing schedule with hospitalized patients. Three of the six patients died as a result of the errors.

SAFE PRACTICE RECOMMENDATION: Because of the number of fatalities from errors with oral methotrexate, clinicians should consider it a high alert medication. As such, there are several measures that can help reduce the risk of an error when oral methotrexate is prescribed:
  • Build alerts in electronic prescribing systems and pharmacy computers to warn clinicians whenever doses of oral methotrexate have been entered (and to remind staff to check the indication with the patient in a retail setting). Configure the systems to avoid defaulting to a daily dosing schedule.
  • Have a pharmacist conduct a prospective drug utilization review before dispensing oral methotrexate to determine its indication for use, verify proper dosing, confirm the correct dosing schedule on medication administration records and prescription labels, ensure staff and patient education, and promote appropriate monitoring of the patient.
  • Establish a system that ensures that outpatients receive counseling when picking up new prescriptions and refills (e.g., mark the bag with a red flag to alert clerical staff that counseling is required, not optional).
  • Provide patients with clear written instructions that name a specific day of the week for taking the tablet(s). When possible avoid choosing Monday since it could be misread as "morning." Prepare instructions in big print to assist elderly patients with poor eyesight.
  • Advise patients to contact their physician if they miss taking a dose. Tell them that a flare-up of the disease is unlikely with one missed dose.
  • Ensure that written drug information leaflets are given to patients and that they contain clear advice about the weekly dosage schedule, not a daily dosing schedule.
  • Explain to patients that taking extra doses is dangerous. Encourage feedback to ensure that the patient understands the weekly dosing schedule and that the medication should not be used "as needed" for symptom control.
  • Solicit help from a responsible caregiver if the patient appears to have cognitive or severe sensory difficulties.
  • Prescribe the drug as a dose pack (e.g., RHEUMATREX by Lederle), which helps to reinforce the weekly dosing schedule.
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