Effect of metoclopramide given before atropine sulphate on lower oesophageal sphincter tone

The effects on lower oesophageal sphincter (LOS) tone of sequential intravenous injections of metoclopramide 10 mg/atropine 0,6 mg and atropine 0,6 mg/metoclopramide 10 mg, given randomly on separate occasions to 8 healthy volunteers, were studied. The administration of metoclopramide increased mean LOS pressure by 13,6 cm H2O (P less than 0,001). Subsequent injection of atropine failed to lower LOS pressure significantly, LOS pressure being sustained at a mean of 11,2 cm H2O above basal control levels (P less than 0,01). In contrast, injection of atropine at a later date in the same subjects lowered the average LOS pressure by 10,5 cm H2O (P less than 0,001), and subsequent intravenous injections of metoclopramide restored LOS pressure to basal levels. The results of this study suggest that metoclopramide should be given prior to atropine before induction of general anaesthesia to counteract the deleterious effects of atropine on LOS tone, thereby helping to reduce the chances of regurgitation and pulmonary aspiration of acid gastric contents.