Background: Diphemanil can be useful in some neonates presenting with bradycardia due to vagal hyperreflectivity. Paradoxically, this drug may induce atrio-ventricular (AV) block in premature babies.
Case reports: Case no 1. A premature neonate suffering from acute respiratory distress from birth required respiratory support, antibiotics and caffeine. Despite this treatment, he underwent many episodes of apnea, and bradycardia that appeared on day 4 and did not respond to IV doxapram (1 mg/kg/h). He was given diphemanil on day 9 (10 mg/kg/d) and permanent bradycardia with complete AV block and a normal QT interval appeared 2 days later. Cessation of diphemanil and administration of IV isoprenaline led to a normal sinusal rhythm, but there were bladder, intestinal and ocular signs of atropinic intoxication. A complete definitive recovery occurred 5 days after cessation of diphemanil. Case no 2. A premature neonate developed episodes of apnea 2 days after birth. These episodes persisted and were complicated by bradycardia on day 4 despite administration of caffeine. Vagal stimulation on day 7 was positive and the infant was then given diphemanil (10 mg/kg/d). Permanent bradycardia occurred 2 days later, with partial AV block and a normal QT interval. The child recovered a normal sinusal rhythm 2 days after cessation of diphemanil.
Conclusions: Anticholinergic therapy may cause permanent bradycardia due to AV block in premature infants. This therapy should not be given to premature infants without a prior ECG. Doses lower than those used in infants are recommended.