Gastric emptying of liquids is delayed by co-ingesting solids: a study using salivary paracetamol concentrations

Background: Paracetamol concentrations in plasma, a frequently used index of gastric emptying (GE) of liquids, are closely correlated with those in saliva. GE of liquids is delayed by co-ingesting solids. No researchers have used salivary paracetamol concentrations to show this phenomenon. The aim of this study was to elucidate whether salivary paracetamol concentrations can detect the food-induced delay in liquid GE. Methods: Paracetamol absorption was measured twice in five healthy male volunteers. Following an overnight fast, they received 10 mg/kg paracetamol in 200 ml water alone on one occasion, and received this solution after consuming a 400 kcal-containing cookie on another occasion. After thorough rinsing of the month, 1 ml saliva was obtained, simultaneously with 2 ml blood, at 0, 0.25, 0.5, 0.75, 1.0, 2.0, 3.0, 4.0, and 6.0 h after paracetamol intake. The peak concentration (C_max), the time to C_max (t_max), the area under the curve (AUC), and C_max/AUC in plasma were calculated. Salivary C_max and t_max were also determined. Results: Plasma C_max and AUC were not significantly different between the two occasions. In contrast, significant differences in plasma t_max and C_max/AUC (P < 0.05) established the food-induced delay in GE. Salivary t_max could detect the delayed GE, whereas salivary C_max could not. Conclusions: Salivary t_max can document the solid meal-induced delay in liquid GE. Received: December 10, 2001 / Accepted: March 8, 2002 Reprint requests to: Y. Kuyama Editorial on page 877