Question 1

What is the main difference between enteral and parenteral routes of compound administration?

Accepted Answer

Enteral administration delivers compounds via the digestive tract, where the substance undergoes hepatic metabolism before entering the bloodstream. Parenteral routes, such as intravenous or intramuscular injection, bypass the liver, resulting in higher bioavailability. This first-pass metabolism difference significantly affects how quickly and completely the compound reaches systemic circulation.

Question 2

Why is sterility important when preparing injection solutions for animal studies?

Accepted Answer

Sterile preparation prevents introducing pathogens into the animal during injection. Both the injection material and the needles and syringes must be sterile to avoid infection. Contamination can compromise animal health and invalidate experimental results, making sterility a fundamental consideration before any compound administration procedure.

Question 3

How does needle gauge selection relate to injection solution viscosity?

Accepted Answer

Solution viscosity determines needle selection because thicker solutions require larger gauge needles to pass through. For mice and rats, 20 to 30 gauge needles are typically used in parenteral administration. The solution should flow through at least one needle, and the smallest gauge feasible is chosen if the solution passes through multiple needle sizes.

Question 4

What are the advantages of subcutaneous injection compared to other parenteral routes?

Accepted Answer

Subcutaneous injection allows safe administration of larger volumes by placing material between skin layers and muscle in a virtual space created by lifting the skin. Although absorption is slower than other routes, this provides a more sustained effect. The technique is relatively simple and carries lower risk of complications compared to intramuscular or intravenous injection.

Question 5

Why must intravenous injections target the lateral caudal tail veins rather than the ventral midline?

Accepted Answer

The lateral caudal tail veins on the sides of the tail are suitable for injection because they deliver compounds directly into the circulatory system. The artery running along the ventral midline is not suitable for injection purposes. Proper vein selection ensures effective delivery and prevents tissue damage from injecting into arterial or subcutaneous spaces.

Question 6

What precautions should be taken during intramuscular injection to prevent tissue damage?

Accepted Answer

Inject material slowly and steadily, as rapid injection causes tissue trauma. Avoid repositioning the syringe during injection to prevent muscle damage. For the gluteal muscle, insert the needle to a maximum depth of 5 mm; for the gastrocnemius, use 3 mm maximum. Improper or repeated injections can cause nerve damage resulting in paralysis or muscle necrosis.

Question 7

How does intraperitoneal injection absorption compare to other parenteral routes?

Accepted Answer

Although intraperitoneal injection is classified as parenteral administration, its absorption mechanism is actually more similar to oral dosing. The compound is injected directly into the peritoneal cavity, allowing safe delivery of large volumes. This route provides intermediate absorption rates compared to subcutaneous and intravenous routes, making it useful for specific experimental applications.

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