Reactions 1745, p3 - 23 Mar 2019 Clearer methotrexate dosing instructions needed Clearer dosing instructions are required in product information documents for methotrexate products, says Marian Attalla from the Uppsala Monitoring Centre. Methotrexate is approved for use in the treatment of rheumatoid arthritis and psoriasis (given as a weekly dose - which can be divided into three doses for the tablet formulation to be taken within 24 hours, at 12-hour intervals), as well as the treatment of cancer (given as single doses for ≤5 consecutive days, followed by a 2-week rest period before starting the next cycle). Between 2009 and January 2018, there were 24 case reports of an incorrect methotrexate administration rate, with 13 of these being from France. In terms of formulation, 19 cases involved administration of oral methotrexate and the remaining 5 cases involved IV methotrexate. The oral methotrexate recipients received daily doses instead of weekly doses, and it appears that in most cases, the patient did not understand that the drug was to be taken weekly and not daily. A prescription error was only reported in one case. The top five adverse reactions reported following methotrexate included mouth ulceration, thrombocytopenia and gastritis (4 cases each), followed by pancytopenia and pharyngitis (2 cases each). Recovery from these events occurred in the majority of cases (n =15), but two deaths were also reported. Marian Attalla highlighted that "the dosing instructions can be particularly confusing in the cases where the weekly dose is divided into three doses to be...