"Capsule" - what is it, definition of the term
A capsule is a solid oral dosage form comprising a soluble shell that encloses a powdered, granulated, or liquid active substance; the shell—usually gelatin or a plant‑based polymer—dissolves in the gastrointestinal tract to release its contents, ensuring precise dosing, protection of sensitive ingredients, and taste masking, and it is commonly employed to deliver compounds to laboratory rats and mice.
Detailed information
The sealed delivery form used in laboratory rodent studies consists of a rigid outer shell and a liquid or powdered core. The shell is typically fabricated from gelatin, hydroxypropyl methylcellulose, or a polymer blend that resists degradation until the point of administration. Internal contents may include pharmacological agents, nutrients, or diagnostic tracers, each stabilized by excipients such as sorbents, buffers, or preservatives.
Manufacturing involves precise filling under aseptic conditions. The process starts with the preparation of the core material, followed by encapsulation in a pre‑formed shell using a rotary die or compression technique. Quality control checks include uniformity of weight, wall thickness, and dissolution rate, ensuring reproducible exposure for each animal.
In rodent experiments, the sealed form offers several advantages. Oral delivery is achieved by direct gavage or incorporation into feed, providing accurate dosing without the need for repeated handling. Intraperitoneal or subcutaneous injection is possible when the shell dissolves rapidly, releasing the active compound into the circulation. The device protects sensitive substances from gastric acidity and enzymatic breakdown, preserving bioavailability.
Safety considerations focus on material biocompatibility and the potential for allergic reactions. Gelatin‑based shells may elicit immune responses in certain strains; synthetic polymers reduce this risk but require validation of non‑toxicity. Disposal protocols mandate autoclaving or chemical decontamination to prevent environmental contamination.
Key parameters for selecting a suitable delivery unit for rats and mice include:
- Size: Diameter ranging from 2 mm to 5 mm, matching the animal’s swallowing capacity.
- Wall composition: Gelatin for rapid dissolution, cellulose derivatives for delayed release.
- Core stability: Lyophilized powders for temperature‑sensitive agents, aqueous solutions for immediate effect.
- Release profile: Immediate, sustained, or targeted release based on polymer coating thickness.
Proper documentation of batch numbers, storage conditions, and administration dates is essential for reproducibility and regulatory compliance in preclinical studies.