Researchers warn of IV acetaminophen dosing errors

Researchers are warning pediatricians, pediatric hospitalists, and intensivists of the potential for intravenous acetaminophen dosing errors, especially in young patients under 2 years old.

Authors Richard C. Dart, MD, PhD, and Barry H. Rumack, MD, both from the Rocky Mountain Poison and Drug Center, Denver, Colo., discuss their concerns for potential overdosing due to clinician dose miscalculation in the February issue of Pediatrics.

“Experience from Europe indicates that serious dosing errors are likely to occur,” the authors wrote. Dart and Rumack note that Europe saw 23 cases of single or repeated dosing errors in children under 1 year old, including 1 that was fatal.

“Most events have involved a 10-fold dosing error in small children caused by calculating the dosage in milligrams, but then administering the solution in milliliters. The solution is 10 mg/mL; therefore, a 10-fold overdose occurs,” the authors wrote.

In November 2010, FDA approved Ofirmev (Cadence Pharmaceuticals), the first intravenous formulation of acetaminophen for the management of mild-to-moderate pain, the management of moderate-to-severe pain with adjunctive opioid analgesics, and the reduction of fever. The US product is formulated in a 10 mg/mL solution.

Although the product is not approved for use in children under 2 years old, the researchers say that off-label use can be expected, given that oral preparations are often difficult to administer to young children, and physicians can anticipate dosing errors.

The authors provide best practices for evaluating and managing intravenous acetaminophen dosing errors, including advising that a serum acetaminophen concentration be drawn 4 hours after the infusion was started, or as soon as possible thereafter if the dose exceeded 150 mg/kg, or if there is doubt about the exact dose.

If the serum acetaminophen concentration plots above the treatment line on the Rumack-Matthew nomogram, treatment with acetylcysteine should be initiated, the authors advise.

“If the dose of acetaminophen infused is known to be 150 mg/kg after a single dosing error, no further evaluation is needed,” Drs Dart and Rumack write.

In addition, they advise physicians to proactively work with their hospital’s pharmacy and nursing staff when intravenous acetaminophen is added to the formulary to raise awareness of the potential for error. When dosing errors occur, physicians should report them to their regional poison center.