[Onset of effect of an i.v. ranitidine bolus]

Ranitidine 50 mg or 0.9% saline was given i.v. to 12(6) volunteers and pH and volume of the gastric aspirate was measured in short-time intervals over a period of 6 hours. There was an increase in pH above 4 in all subjects starting within 30 min after ranitidine injection. Concomitantly volume secretion was reduced to 35-50%. i.v. administration of ranitidine 30-45 min before induction of anaesthesia should, therefore, reduce the number of patients theoretically at risk of acid-induced pulmonary damage.