Introduction to Capsules
Capsules are solid dosage forms in which the drug is enclosed in a small shell made of gelatin or other suitable materials. They are easy to swallow, mask unpleasant tastes, and allow accurate dosing. Capsules offer a convenient way to deliver powders, granules, semi-solid, or liquid medicines.
Types of Capsules
Capsules are mainly of two types based on the nature of their shell:
- Hard Gelatin Capsules (HGC)
- Soft Gelatin Capsules (SGC)
Hard Gelatin Capsules (HGC)
Hard gelatin capsules are the most commonly used capsules. They consist of two parts—the body and the cap. These two parts fit together to hold the drug. They are ideal for dry powders, capsules-within-capsules, pellets, granules, and low-viscosity liquids that do not dissolve gelatin.
Composition of Hard Gelatin Capsules
- Gelatin – obtained from collagen of animals
- Plasticizers – like sorbitol for flexibility
- Colourants – for product identification
- Preservatives – like parabens
- Opacifiers – e.g., titanium dioxide for light protection
Advantages of Hard Gelatin Capsules
- Easy to swallow due to smooth surface
- Masks taste and smell of the drug
- Flexible dosage – can hold powder, pellets, or mini-tablets
- Visually appealing and customizable
- Simple to manufacture on a large scale
Disadvantages of Hard Gelatin Capsules
- Not suitable for highly soluble liquids
- Moisture-sensitive – gelatin becomes soft or brittle
- Higher cost than tablets
Sizes of Hard Gelatin Capsules
Hard gelatin capsules come in different sizes for humans, ranging from size 000 (largest) to size 5 (smallest). Larger sizes are used for veterinary purposes.
Soft Gelatin Capsules (Softgels)
Soft gelatin capsules are one-piece, elastic, hermetically sealed capsules that contain liquids, oils, or semi-solids. They dissolve quickly in the stomach and increase the bioavailability of poorly soluble drugs.
Composition of Soft Gelatin Capsules
- Gelatin
- Plasticizers – glycerin, sorbitol
- Water – higher content than HGC
- Preservatives
- Colourants and Opacifiers
Advantages of Soft Gelatin Capsules
- Ideal for oils and liquid drugs
- Improves absorption and bioavailability
- Elegant and easy to swallow
- Hermetically sealed – better stability
- Accurate and uniform dosing
Disadvantages of Soft Gelatin Capsules
- More expensive than hard capsules
- May absorb moisture and become sticky
- Special machines needed for production
Differences Between Hard and Soft Gelatin Capsules
| Hard Gelatin Capsules | Soft Gelatin Capsules |
|---|---|
| Two-piece capsule (body + cap) | One-piece sealed capsule |
| Used for powders and pellets | Used for oils, liquids, and semi-solids |
| Less flexible shell | Soft and elastic shell |
| Lower cost, easier manufacturing | Higher cost, specialized equipment |
Storage Requirements
Capsules must be protected from humidity, heat, and light. Ideal storage conditions are:
- Hard gelatin capsules: 15–25°C with 35–55% humidity
- Soft gelatin capsules: 15–30°C with humidity below 50%
Applications of Capsules
Capsules are widely used in:
- Prescription medicines
- Over-the-counter supplements
- Herbal preparations
- Nutritional oils like fish oil and vitamin E
- Drugs with poor taste or odor
