The authors report the case of a 21 year old woman with a congenital long Q7 syndrome who had several syncopal attacks at least one of which was caused by torsades de pointe. This sudden complication was attributed to the simultaneous prescription of Spiramycine and Mequitazine over a 48 hour period. These two drugs are not considered to be predisposing factors for torsades de pointe despite the fact that they belong to two families of drugs which can trigger this type of arrhythmia. The withdrawal of this treatment led to the complete regression of the syncopal episodes with a follow-up of two years and a significant shortening of the initial QTc interval which remained, nevertheless, longer than normal. This case underlines the potential risks of drug associations of these two families of drugs, especially in patients with the congenital long Qt syndrome.