Pharmaceutical Science: Capsules Overview

Study Notes

Drugs with unpleasant odors or tastes can be administered in tasteless capsules.
Smooth texture, becoming slippery when moist, allows easy swallowing.
Gelatin's ready solubility at gastric pH ensures rapid drug release in the stomach.
Capsules are visually appealing.
Capsules provide an accurate dosage.
Capsules are generally tasteless and odorless when swallowed, unlike liquid medications.
Shapes and colors, along with manufacturer's markings, help with capsule identification.

Hygroscopic drugs cannot be encapsulated.
Concentrated preparations requiring prior dilution are unsuitable for capsules, as they may irritate the stomach.

Gelatin is a heterogeneous product created by hydrolyzing animal collagen (obtained from animal bones and frozen pork skin).
There are two types of gelatin: Type A (derived from pork skin via acid treatment) and Type B (derived from bones and skin via alkaline processing).
Differences in isoelectric points cause solubility variations at different pH values.
Gelatin is stable when dry but can decompose when moist due to microbial activity.
Gelatin is insoluble in cold water but dissolves in hot water and warm gastric fluids.
Gelatin, being a protein, is digested by proteolytic enzymes and absorbed.
Gelatin is non-toxic.

Used for administering solid medications.
Consist of two parts: a body and a cap.
Can be clear, colorless, and tasteless.
Commonly colored with FD&C and D&C dyes.
May contain combinations of colorants to improve identification.
Normally contain 13% to 16% moisture.
Capsules can become misshapen if exposed to high humidity.
Capsules can become brittle in extremely dry conditions.
Often packaged with a desiccant (e.g., silica gel) to prevent moisture absorption.
Gelatin capsules are not suitable for aqueous liquids.

Gelatin: Creates the shell, protects contents, masks taste/odor.
Plasticizers: Improve softness and elasticity (e.g., phthalates, glycerin).
Preservatives: Prevent microbial growth (e.g., methyl paraben, sorbic acid).
Solvents: Improve drug solubility (e.g., propylene glycol, PEG 400, ethanol).
Darkening agents: Reduce transparency (e.g., titanium dioxide).
Coloring agents: Enhance capsule appearance (e.g., FD&C and D&C dyes.)
Flavors: Enhance taste and odor.
Sugars: Add sweetness (e.g., sucrose).
Acids: Reduce gelatin aldehyde tanning.
Thickening agents: Adjust gelatin viscosity.
Water: (a component in the manufacturing process.)

The process involves dipping, spinning, drying, stripping, trimming and joining.
Diagrams show the stages of manufacturing.

Capsules may need to be polished to remove adhering powders.
Cleaning techniques range from small-scale manual methods using gauze to industrial processes using vacuum cleaners.
Additional techniques, like imprinting, can add branding to empty capsules.
Special purpose capsules undergo unique treatments to alter solubility delays.
Quality control tests include:
- Weight variation
- Content uniformity
- Disintegration
- Dissolution