The amount of drug or solution that can be safely injected into a rat will depend on the route used to administer.
In some cases both subcutaneous and intramuscular injections can be given in larger volume if divided over several different sites on the rat. It is important to note that only about 0.2 ml of intramuscular injection, for an adult rat weighing 200 grams, may be retained at any one site.
While subcutaneous injections can be done quickly, care should be taken not to inject IV or intramuscular injections rapidly as this could cause the rat to go into cardiovascular failure and lead to death.
It has been recommended to give the smallest volume of drug or solution that will meet the need, particularly if it is likely to be an irritant to tissue.
| Route | Maximum Volume | Comments |
|---|---|---|
| I.D.(intradermal) | 50 to 100 uL (microliters) | Note: microliter is a much smaller amount than milliliter. |
| Sq or s.c. | up to 5 mL | The larger the volume the more slowly absorbed. |
| IM | 0.2 mL | Use more than one site if large volume is required. Too large a volume at one site can cause pain and will not be retained. |
| IV | 2 mL | Inject over 1 to 2 minutes. If greater than 2 mL must be given, then infuse over 5 minutes or longer based on volume to be given. |
Modified from: Experimental and Surgical Technique in The Rat, Second Edition,
H.B. Waynforth & P.A. Flecknell
