A year ago we did a column on dangerous incidents involving methotrexate (see our July 2010 What’s New in the Patient Safety World column “Methotrexate Overdose Due to Prescribing Error”). In that column we described a lawsuit alleging that an elderly patient with rheumatoid arthritis was erroneously prescribed a methotrexate dose on a daily basis instead of the weekly basis for which it was intended. The erroneous dosage was apparently also then continued when the patient was transferred to a longer term care facility. We had seen that exact scenario in the past. And, in fact, ISMP did a Medication Safety Alert on this issue back in 2002 and another alert in 2009.
Now the Pennsylvania Patient Safety Authority has reviewed 6 years worth of incidents in Pennsylvania involving methotrexate errors. The PPSA advisory found over 200 reports of incidents involving methotrexate in Pennsylvania. Wrong dosage accounted for about a third of these incidents and of those with overdosage almost 60% involved confusion between daily dosing vs. dosing intended to be given only once or twice a week.
Methotrexate is used for treating a variety of conditions. In some, for example oncology conditions, it might be used daily. But for others, such as rheumatoid arthritis where it is used as an immunomodulating agent, it is usually given weekly. The errors often occur during the medication reconciliation process. Typically, methotrexate is initially prescribed by a specialist. But the patient is then admitted to either an acute care hospital or a long-term care facility and the dose is mistakenly written as a daily rather than weekly dose.
ISMP had some good recommendations in their 2002 alert. They recommend use of alerts in electronic prescribing systems and pharmacy computer systems to flag orders written for daily methotrexate to be reviewed for correctness. (This, by the way, is a great example where systems mandating entry of the indication for a drug could be very useful.). They also caution that computer systems should avoid default daily regimens for methotrexate. They recommend the pharmacist should do a prospective review before the medication is dispensed, including checking the indication for the drug, the dosage, the dosing schedule, the appropriate monitoring, and the appropriate education of the patient and caregivers. They also recommend that there be outpatient counseling of patients and that outpatient pharmacies should flag the medication so that this counseling takes place when the patient comes in to pick it up. They also recommend that the instructions on the label specify which day of the week the patient should take the methotrexate and the patient should be educated about what to do in the event of a missed dose. Be especially careful that any printed materials provided for patients have the correct weekly wording. Be particularly careful in cognitively impaired patients. Using dose packs may also reinforce the weekly dosing regimen. For those patients discharged from the hospital on methotrexate, ISMP recommends a followup phone call a day or two after discharge to ensure the patient is taking the methotrexate (and other medications) correctly.
We also think that the patient in a long-term care facility is especially vulnerable. In such cases, the original order for methotrexate is usually written by a specialist. The patient is then followed in the LTC facility typically by a primary care physician who may be less knowledgeable about the particular use of methotrexate for that condition. Also, the LTC patient may not be seen by a physician for periods as long as a month. So if a medication reconciliation error has occurred and a patient intended for once or twice weekly dosing is now on daily dosing, the opportunity for toxicity is greatly increased.
Roche WF. Lawsuit claims dosage error at UPMC Passavant led to death. Pittsburgh Tribune-Review. June 10, 2010
ISMP. Beware of erroneous daily oral methotrexate dosing. ISMP Medication Safety Alert. Acute Care Edition. April 3, 2002 issue
ISMP. Methotrexate Overdose. ISMP Medication Safety Alert. Acute Care Edition. April 23, 2009 issue
PPSA. Data Snapshot: Errors Involving Methotrexate. Pa Patient Saf Advis 2011; 8(2): 77-9