Aim: Study of Different Routes of Drug Administration in Mice and Rats
References:
- CPCSEA Guidelines for Laboratory Animal Facility
- Institutional Animal Ethics Committee (IAEC) Standard Operating Procedures (SOPs)
- AVMA Guidelines for the Euthanasia of Animals
Objective:
The objective of this experiment is to acquire practical knowledge and hands-on experience in administering drugs through different routes—oral, intravenous, intraperitoneal, subcutaneous, intramuscular, and intranasal—in mice and rats. This includes understanding the anatomical sites, proper handling, dosage calculation, and post-procedural care, while ensuring the welfare of the animals in compliance with ethical standards.
Materials Required:
Sterile syringes and needles (ranging from 23G to 30G), oral gavage needles, drug solutions of known concentration, intravenous catheters (if required), personal protective equipment (PPE) such as gloves and lab coats, anesthetics (if needed), animal restraining devices, disinfectants, cotton swabs, and record-keeping sheets for documentation.
1. Oral (PO) Administration:
In oral drug administration, the compound is delivered directly into the stomach using a gavage needle. The drug solution is prepared and drawn into a syringe fitted with a suitable oral gavage needle. The animal is gently restrained to prevent injury, and the needle is inserted carefully through the oral cavity into the esophagus, avoiding the airway (trachea). The drug is then administered slowly to prevent choking or aspiration. Following administration, the animal is observed for any immediate signs of distress before being returned to its housing.
2. Intravenous (IV) Administration:
Intravenous administration involves injecting the drug directly into a vein, commonly the lateral tail vein in rodents. The animal is placed in a restraining device, and the tail is warmed using warm water or a heat lamp to dilate the veins. A fine needle (typically 25–27G for mice, 23–25G for rats) is inserted into the vein at a shallow angle. The drug is slowly administered, ensuring that it enters the bloodstream properly. Gentle pressure is applied post-injection to prevent hematoma formation, and the animal is monitored closely for any adverse reactions.
3. Intraperitoneal (IP) Administration:
In IP administration, the drug is injected into the peritoneal cavity. The animal is restrained with its head slightly downward to shift the internal organs upward, reducing the risk of puncture. A sterile needle is inserted into the lower right quadrant of the abdomen at a 30–40° angle. Aspiration is performed briefly to ensure the needle has not entered a blood vessel or the bladder. Once confirmed, the drug is injected slowly. The animal is then monitored for any signs of discomfort or complications.
4. Subcutaneous (SC) Administration:
This method involves injecting the drug into the space just beneath the skin. The animal is restrained carefully, and the skin at the back of the neck or between the shoulders is lifted to form a tent. A needle is inserted into this tented area, and the drug is administered slowly. This route is relatively safe and causes minimal discomfort to the animal. After the injection, the site is checked for swelling or leakage, and the animal is observed briefly before being returned.
5. Intramuscular (IM) Administration:
IM administration requires the drug to be injected directly into the muscle tissue, commonly the quadriceps or gluteal muscles. The animal is restrained securely, and a small needle (27–30G) is inserted at a 90° angle into the muscle. The drug is injected slowly to avoid tissue damage. After the injection, gentle pressure is applied to the site to reduce the chance of bleeding or swelling, and the animal is observed for pain or lameness.
6. Intranasal (IN) Administration:
This route is used for localized or systemic drug delivery through the nasal mucosa. The animal is held in a supine position with the head slightly elevated. A micropipette or fine syringe is used to place a small drop of the drug solution at the opening of the nostril. The animal is allowed to inhale it naturally. Care must be taken to avoid excessive volume which may lead to aspiration. After administration, the animal is observed for any signs of respiratory discomfort.
Safety Precautions:
Use of proper PPE is mandatory throughout all procedures. Drugs must be sterile and dosed accurately based on body weight. Animals should be handled gently to minimize stress. All injections must be performed under aseptic conditions using the correct gauge and route-specific technique.
Ethical Considerations:
Prior approval from the Institutional Animal Ethics Committee (IAEC) is essential. All procedures must follow the 3Rs principle—Replacement, Reduction, and Refinement. Any discomfort or pain should be minimized, and animals must be handled with care and compassion.