Abstract

A previous report indicated abnormally rapid heart rates in patients with Down's syndrome given atropine, and the possibility of a potentially dangerous idiosyncrasy to atropine in these patients has been raised. The heart rate response to atropine in doses of 30 to 60 μg/kg was studied in 14 children and 11 adults with Down's syndrome, using for control subjects 7 children and 9 adults with mental retardation not due to Down's syndrome. The heart rate response to atropine was similar in the patients with and without Down's syndrome. Peak heart rates occurred at 25 μg/kg of atropine after an initial slowing with 5 to 7 μg/kg. The heart rates of the subjects with Down's syndrome tended to be lower than those of the controls after propranolol was given in addition to the atropine, but the significance of this was not known. Ophthalmic atropine produced a more rapid mydriasis in the Down's syndrome patients, but the degree and duration of the pupillary dilatation was the same as in the control subjects.