Flecainide/milk interaction
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Toxicity in a child following reduced milk intake: case report A boy aged 8 years 3 months developed flecainide toxicity following reduced milk intake. The boy, whose history included innocent murmurs, a postulated benign form of acrocyanosis or Raynaud’s phenomenon and supraventricular tachycardias (SVTs), was started flecainide therapy around 5 years of age. Flecainide was started at 45mg (2 mg/kg/dose) twice daily [route not stated] as a maintenance antiarrhythmic. At that time, he weighed 21.5kg. He received routine therapeutic drug monitoring, and his flecainide concentrations were persistently subtherapeutic. At 7 years of age, he experienced three episodes of SVT and was treated with adenosine. His family confirmed good medication adherence but reported a heavy milk intake (>750 mL/day) by the patient. His flecainide dose was increased to 50mg twice daily, but he continued to have symptomatic SVT. His flecainide dose was increased stepwise to 75mg twice daily and 100mg twice daily (7.6 mg/kg/day). He was asymptomatic at this dose, but he still had subtherapeutic flecainide levels. He was advised to refrain from drinking milk until at least 30 minutes after taking a dose of flecainide. At 8 years 3 months of age, he became acutely unwell, limp and apnoeic. He required mouth-to-mouth resuscitation, and an ambulance was called. He resumed breathing but remained floppy. When his consciousness returned, he was confused and agitated. He also had increased tone and extensor posturing. The patient received lorazepam to control his agitation. His ECG showed significant broadening of his QRS duration and QT prolongation, consistent with flecainide toxicity. His flecainide concentration, 18 hours after his last dose, was 576 mcg/L. Specific treatment was not given, but subsequent flecainide doses were withheld. He made good improvement. Of note, his milk drinking had considerably decreased before his episode. After the resolution of the patient’s symptoms, he was discharged with a decreased flecainide dose of 75mg twice daily (5.54 mg/kg/day). Subsequently, he was switched from liquid solution to tablets. He remained well controlled aside from two self-correcting episodes. Later on, he received a transcatheter radiofrequency ablation of a concealed left-sided accessory pathway. At last follow-up, he was symptom-free and did not need medications. Author comment: "[W]e remain concerned that it was the decrease in milk drinking that significantly affected the flecainide levels in this child, causing a life-threatening arrhythmia." Thompson B, et al. Decreased milk drinking causing flecainide toxicity in an older child. BMJ Case Reports 2012: [3 pages], 22 Jun 2012. Available from: URL: 803077234 http://dx.doi.org/10.1136/bcr.02.2012.5810 - United Kingdom
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Reactions 22 Sep 2012 No. 1420
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