Age, higher dose, longer treatment predict symptoms in MTX poisoning

Clear communication with patients is necessary to prevent therapeutic errors when prescribing methotrexate (MTX) for the first time, according to a study. Older age, higher total dose, and longer treatment duration are predictive of the presence of clinical manifestations.

The authors carried out this retrospective observational study to determine the predictive factors for the development of clinical manifestations in poisoning due to the erroneous taking of low-dose MTX. Forty-one cases of erroneous administration in nononcologic outpatients were included (July 2008 to March 2020).

All patients were taking MTX for the first time, of which 36 did so on a daily basis instead of weekly. In the remaining five patients, MTX was sold instead of methylergometrine.

Twelve patients (29.3 percent) did not develop any clinical manifestation. Twenty-nine symptomatic patients (70.7 percent) recognized the medication error when they developed clinical manifestations, such as dermatological, haematological, and gastrointestinal symptoms.

In statistical analysis, symptomatic patients were more likely to be older, have received a higher amount of total dose, and be treated for a longer duration. In addition, the probability of being symptomatic increases as a function of age and of total dose.

Asymptomatic patients received folinic acid (30 mg/m²/day) for 5 days, while those with symptoms took folinic acid together with treatments for the specific clinical manifestations. None of the patients were treated with glucarpidase. All of them fully recovered.

“In our experience, age, total dose taken, and number of days of assumption are predictive for the presence/absence of clinical manifestations,” the authors said. “These parameters must be evaluated together to identify patients needing maximum starting treatment with folinic acid and closer monitoring.”