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Administration by Oral Gavage

Description of the Procedure

Liquid compounds may be administered directly into the stomach of mice and rats via a technique called oral gavage. In this procedure a stainless steel bulb tipped gavage needle or a flexible cannula or tube is attached to a syringe and used to deliver the compound into the stomach. Gavage needles come in mouse and rat sizes and lengths. The correct needle or cannula length is equal to the distance from the mouth to just beyond the last rib.

The animal should be gently restrained (grasp the animal by the loose skin of the neck and back) to immobilize the head but not such that the animal vocalizes or shows other signs of distress. Maintain the animal in an upright (vertical) position and pass the gavage needle along the side of the mouth. Following the roof of the mouth, advance the needle into the esophagus and toward the stomach. If resistance is encountered you may be attempting to enter the trachea and you should alter your needle position. After the needle is passed to the correct length, the compound may be injected. If the animal coughs, chokes or begins to struggle after compound administration begins you may be injecting material into the lungs. If this occurs stop and withdraw the needle immediately. If it appears that material has been injected into the lungs the animal should be euthanized. Struggling during administration or excessive force in advancing the needle may lead to rupture of the esophagus or stomach. If you suspect this has occurred the animal should be euthanized. Sedation or anesthesia prior to oral gavage is not recommended as this will increase the risk of aspiration pneumonia.

A video demonstration of oral gavage in the mouse may be viewed on the Procedures With Care website.

Oral gavage training videos for mice and rats (produced by Instechlabs) are also available on YouTube.

Potential Complications

  • Passive reflux if excessive material administered.
  • Aspiration pneumonia if material injected into the trachea.
  • Pharyngeal, esophageal and gastric irritation or injury due to incorrect technique or caustic substances. This may lead to scarring and narrowing of the esophagus and/or gastric openings and esophageal or gastric rupture.
  • Physical and/or psychological stress to the animals. Training and habituation to handling may decrease this.
  • Microaspiration of material into the lungs (Craig MA, Elliott JF. 1999. Contemp Top Lab Anim Sci 38: 18-23.).

The risk of complications may be decreased by using soft (flexible) gavage tubing rather than stainless steel dosing needles.

Reference:

Turner PV, Brabb T, Pekow C, Vasbinder MA. Administration of Substances to Laboratory Animals: Routes of Administration and Factors to Consider. 2011. JAALAS 50 (5): 600-613.