Impact of oral gavage technique of drug-containing microcontainers on the gastrointestinal transit and absorption in rats

Oral gavage is the most common way to administer drug formulations orally to rats. Yet, the technique applied and its influence on gastrointestinal (GI) transit receive little attention. This study aims to investigate the impact of three oral gavage techniques on GI transit and drug absorption utilizing microcontainers (MCs). The MCs were filled with paracetamol and BaSO₄ (1:1 w/w ratio), coated with Eudragit S100, and filled into size-9 gelatin capsules. An in vitro study confirmed the intactness of the coating, and the capsules were administered to rats with air, water, or a piston. X-ray imaging determined the locations of the MCs, and the corresponding plasma concentration of paracetamol established a correlation with the location. The fastest GI transit occurred with air-dosing, while water-dosing caused delayed gastric emptying for 3h with non-quantifiable paracetamol absorption. Piston-dosed MCs were retained in the stomach for up to 1h, though for 3h in one rat. Air-dosing caused discomfort and stress in rats, thus limiting its ethical and physiological relevance. Water-dosing confined its use due to delayed gastric emptying. In conclusion, the oral gavage technique affected the GI transit of MCs and, consequently, drug absorption. Piston-dosing appeared to be the superior dosing technique.