Capsules are solid dosage forms in which one or more drug substances are enclosed in a small, easy-to-swallow shell. The shell is usually made of gelatin or a non-gelatin alternative. Capsules improve patient acceptance by masking unpleasant tastes and odors and are widely used for powders, granules, and even some liquids.
Advantages of Capsules
- Easy to swallow and handle
- Mask bitter taste and foul odor of drugs
- Allow accurate dosing
- Offer flexibility in formulation (powders, granules, mini-tablets)
- Fewer excipients compared to tablets
- Suitable for drugs with poor compression properties
Disadvantages of Capsules
- Gelatin shells may soften in high humidity
- Unsuitable for highly soluble salts (risk of gastric irritation)
- Temperature-sensitive and moisture-sensitive
- Risk of sticking together if not stored properly
Types of Capsules
1. Hard Gelatin Capsules (HGC)
Two-piece capsules consisting of a body and a cap. Used for powders, granules, pebbles, and mini-tablets.
2. Soft Gelatin Capsules (SGC)
One-piece, hermetically sealed capsules used for oils, vitamins, and liquid drugs. The shell contains gelatin, plasticizer, and preservative.
Composition of Capsule Shells
- Gelatin: Derived from collagen of animal bones or skin
- Plasticizers: Glycerin, sorbitol (mainly in soft gels)
- Colorants: Improve identification and appearance
- Opacifiers: Titanium dioxide for light protection
- Preservatives: Prevent microbial growth
Manufacturing of Hard Gelatin Capsules
1. Shell Production
- Dipping stainless-steel pins into gelatin solution
- Drying the coated pins
- Removing shells from pins
- Cutting to required length
- Joining body and cap
2. Filling of Capsules
Capsules can be filled with:
- Powders
- Granules
- Pellets
- Mini-tablets
Filling Methods
- Hand filling: For small batches or trials
- Automatic capsule filling machines: For large-scale production
Manufacturing of Soft Gelatin Capsules
Soft gels are produced by the rotary die process where the shell is formed, filled, and sealed in a single step.
Suitable Materials for Soft Gels
- Oils (fish oil, vitamin E)
- Non-aqueous solutions
- Suspensions
Quality Control Tests for Capsules
- Weight variation: Ensures correct fill quantity
- Disintegration time: Determines breakup in body fluids
- Dissolution testing: Measures drug release rate
- Content uniformity: Ensures accurate dosage
- Moisture content: Important for gelatin shells
- Shell integrity: No cracks or deformities
Storage and Packaging
- Store in tightly closed containers
- Avoid high humidity (gelatin can absorb moisture)
- Protect from heat and light
- Use blister packs, HDPE bottles, or strip packs
Patient Counseling Points
- Swallow capsules whole unless instructed otherwise
- Do not open the capsule unless approved by a pharmacist
- Store in a cool, dry place
- Take with sufficient water to avoid throat irritation
Detailed Notes:
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