The effect of intramuscular pirenzepine on esophageal contractile activity and lower esophageal sphincter pressure under fasting conditions and after a standard meal. A double blind study.

In two studies, each on 16 healthy volunteers, the effects of pirenzepine on esophageal and lower esophageal sphincter (LES) contractile activity were studied under double blind conditions. One study was carried out on subjects who had fasted, the other on subjects who had ingested a standard meal. Each subject underwent two experiments, one with i.m. injection of 0.2 mg/kg body weight pirenzepine, the other with an injection of solvent. Heart rate, respiratory rate, electroencephalogram, and reaction time to acoustical stimuli were recorded to control for cardiovascular, respiratory and central nervous effects respectively. Pirenzepine under both fasting and nonfasting conditions caused significant decreases in number, amplitude, and duration of swallow-contractions. LES pressures under both conditions were significantly lower after pirenzepine than after the solvent. Pirenzepine furthermore caused a significant heart rate deceleration and respiratory acceleration, as well as an increased power in the faster Beta- and decreased power in the Alpha-range of the EEG. In conclusion, pirenzepine inhibits esophageal and LES contractile activity and also affects the central nervous system by a direct or indirect mechanism. An application of pirenzepine in hypertensive states of the LES and the esophagus seems possible and deserves further investigation.