Effect of intravenous atropine and methylatropine on heart rate and secretion of saliva in man.

Intravenous atropine sulphate (0.25, 0.40, 0.75 and 1.50 mg), atropine methylnitrate (0.08, 0.13 and 0.25 mg) and saline were given to 72 healthy medical students. The effects on heart rate and rhythm, systolic and diastolic blood pressure and salivary secretion were studied. Salivation was inhibited by all the doses of the two drugs. There was a clear dose-response relationship and methylatropine was about 3 times as potent as atropine. Heart rate was accelerated by 0.75 and 1.50 mg atropine, and 0.25 mg methylatropine, whereas 0.25 mg atropine and 0.08 and 0.13 mg methylatropine induced bradycardia, which was considered to be due to a peripheral action. It is suggested that the drugs act as partial agonists at muscarinic receptors. No clear effect on blood pressure was seen, except for the highest dose of atropine, after which the diastolic pressure was increased. 20 out of 59 subjects who received anticholinergics developed supra-ventricular arrhythmias; with both drugs periods of nodal rhythm were most common. They appeared shortly after the injection and usually lasted for a few minutes.