Disadvantages include its nonphysiological and invasive nature, the confounding effects of the delivery vehicle and anesthesia, and the fact that it bypasses the upper respiratory tract.
[1] Their results provide a quick screen of potential toxicity and can be used to test its mechanism, but may not be directly applicable to occupational exposure that occurs over an extended period.
[3] Some of these difficulties are overcome by another method, pharyngeal aspiration, which is less technically difficult and causes less trauma to the animal,[4] and has a pulmonary deposition pattern more similar to inhalation.
Generally, short-acting inhaled anesthetic drugs such as halothane, metaphane, or enflurane are used during the instillation procedure.
Saline solution is usually used as a delivery vehicle in a typical volume of 1–2 mL/kg body weight.