Administration of substances to laboratory animals: routes of administration and factors to consider

Abstract

Administration of substances to laboratory animals requires careful consideration and planning to optimize delivery of the agent to the animal while minimizing potential adverse experiences from the procedure. For all species, many different routes are available for administration of substances. The research team and IACUC members should be aware of reasons for selecting specific routes and of training and competency necessary for personnel to use these routes effectively. Once a route is selected, issues such as volume of administration, site of delivery, pH of the substance, and other factors must be considered to refine the technique. Inadequate training or inattention to detail during this aspect of a study may result in unintentional adverse effects on experimental animals and confounded results.

Figure 1.

(A) Rat voluntarily consuming nutritional supplement from a syringe. Photo courtesy of Colette Wheler. (B) Macaque voluntarily drinking medication from a syringe. Photo courtesy of Andrew Winterborn. (C) Pig voluntarily accepting medication when administered in a marshmallow. (D) Oral gavage of fish. Photo courtesy of Gerald Johnson.

Figure 2.

Chronic nasogastric catheter placement in a rabbit for enteral nutrition. Photo courtesy of Colette Wheler.

Figure 3.

Different routes of skin administration of substances. Depicted are intramuscular (IM), intravenous (IV), subcutaneous (SC), and intradermal (ID) routes. Illustration courtesy of Gianni Chiappetta.

Figure 4.

Epidural (ED) compared with intrathecal (IT) injections in the distal lumbar spine. Illustration courtesy of Gianni Chiappetta.

Figure 5.

(A) Deep anesthesia of a fish with tricaine methane sulfonate (MS222), achieved by immersion in aqueous solution with the drug. Drug is taken up across the gills during respiration and, to a lesser extent, across the skin. Photo courtesy of Gerry Johnson. (B) Amphibians may be similarly dosed in aqueous chambers as in the Xenopus laevis depicted; however, substance uptake is solely through trancutaneous absortion.

Figure 6.

Inadvertent esophageal rupture (arrows) with food contamination and local cellulitis after oral gavage in a mouse. Photo courtesy of David Hobson.

Figure 7.

Photomicrograph of atrial thrombosis with secondary bacterial infection and myocarditis in a rat with a chronic indwelling jugular vein catheter. A large septic thrombus (T; bacterial colonies indicated by arrows) is firmly adherent to the endocardium and there is significant infiltration of the myocardium (C) with neutrophils. The thrombus has not entirely occluded the atrium, as a small lumen (L) is present. Hematoxylin and eosin stain; magnification, ×40.

Figure 8.

Photomicrograph demonstrating multifocal suppurative encephalitis with perivascular neutrophilic cuffing (arrows) after inadvertent contamination of an indwelling jugular vein catheter in a rat. Hematoxylin and eosin stain; magnification, ×40. Photo courtesy of Leah Schutt.

Figure 9.

Photomicrographs demonstrating incidental findings. (A) Raft of epithelial cells (arrows) forming microthrombus within a pulmonary vessel of a chronically infused rat. Hematoxylin and eosin stain; magnification, ×200. Photo courtesy of Igor Mikaelian. (B) Hair shaft embedded centrally within pulmonary microthrombus of rat receiving a bolus IV injection. Hematoxylin and eosin stain; magnification, ×400. Photo courtesy of Heather Workman.