Contamination of antibiotics resulting in severe pediatric methadone poisoning

To report an accidental contamination of antibiotic suspension by methadone that occurred in a retail Canadian pharmacy, leading to severe poisoning in a young child.

A 4 1/2-year-old healthy Asian boy was prescribed amoxicillin suspension for cough and fever. Shortly after receiving the second dose of 5 mL he became drowsy and less responsive. On admission, he was arousable by deep pain, and pinpoint pupils were noted. A urine sample sent for a toxicology screen revealed the presence of methadone and its metabolite. Blood methadone concentrations were 0.23 and 0.14 mg/L, five and nine hours after the second dose of amoxicillin was given, respectively. The amoxicillin suspension was tested for methadone and was found to have a concentration of 2.4 g/L. The child gradually improved and was discharged on day 4 in good condition. The pharmacy in which the antibiotic was dispensed has been a dispensing center for a local methadone maintenance program, and methadone was accidentally mixed with the antibiotics.

In this case, a near fatal outcome occurred when methadone was inadvertently mixed with antibiotics in a community pharmacy. A literature search revealed two previous reports of opiate toxicity in children following ingestion of oral antibiotic preparations.

Prompt action is needed in Canadian pharmacies that dispense methadone in order to minimize such errors in the future. General practitioners, pediatricians, and emergency department physicians should recognize and suspect this rare cause of opiate toxicity in a child. In a patient presenting with a decreased level of consciousness and miosis, with or without respiratory depression, naloxone administration should be considered, whether or not a history of opioid ingestion is obtained.