What Are Pharmaceutical Capsules?
Pharmaceutical capsules are solid dosage forms used to enclose precise quantities of medication, supplements, or herbs. Their outer shell can be made of gelatin (animal-based) or HPMC (plant-based), offering advantages such as ease of swallowing, taste masking, and better content protection.
Types of Capsules:
- Hard Gelatin Capsules (HGC): Two-piece shell, ideal for powders and granules.
- Soft Gelatin Capsules (SGC): Single-piece shell, suitable for oils and semi-solids.
- Vegetarian Capsules: Made from HPMC or pullulan, suitable for sensitive or dietary applications.
Classification of Capsules by Material
Hard Gelatin Capsules (HGC)
- Derived from collagen of animal origin.
- Fast disintegration (5–15 min in stomach).
- Widely used in pharmaceuticals.
Soft Gelatin Capsules (SGC)
- Flexible, elastic shell using plasticizers.
- Suitable for fat-soluble vitamins and oils.
HPMC or Plant-Based Capsules
- Non-animal origin, stable under humid conditions.
- Preferred in supplements and health products.
Capsule Size Guide: From 000 to 5
Capsule sizes are standardized internationally. The most common sizes range from 000 (largest) to 5 (smallest). Choosing the right size depends on the fill weight and bulk density of the formulation.
Capsule Size Volume (ml) Max Fill Weight (mg) (with 0.8 g/ml bulk density) Overall Length (locked) External Diameter (cap) Use Case
000 1.37 ~1100 26.1 mm 9.91 mm Herbal, high-dose
00 0.95 ~750 23.3 mm 8.56 mm Supplements
0 0.68 ~500 21.7 mm 7.64 mm Pharmaceuticals
1 0.50 ~400 19.4 mm 6.91 mm Low-dose meds
2 0.37 ~300 18.0 mm 6.35 mm Pediatric
3 0.30 ~200 15.9 mm 5.85 mm Small dose
4 0.21 ~120 14.3 mm 5.33 mm Microdosing
5 0.13 ~60 11.1 mm 4.91 mm Veterinary/pediatrics
What Is the Most Common Capsule Size?
The most commonly used capsule sizes are:
- Size 0: Standard for 500 mg formulas in both pharmaceutical and nutraceutical products.
- Size 00: Popular in dietary supplements; larger volume (~950 mg).
- Size 1–3: Used for lower-dose medications and pediatric uses.
Capsule size preference depends on ease of swallowing, target population, and the density of the filling material.
How to Choose the Right Capsule Size?
When choosing a capsule size, consider the following:
- Weight of Active Ingredients
- Bulk Density of the Powder
- Intended Use (oral, inhaled, etc.)
- Age of the Patient (children vs. adults)
- Machine Compatibility (for mass production)
Pharmacists often use nomograms to calculate the best capsule size based on these variables.
What Are Capsules Made Of?
Capsules generally contain:
- Shell material: Gelatin, HPMC, or pullulan
- Plasticizers: Glycerin or sorbitol for softgels
- Colorants: Titanium dioxide, iron oxides
- Optional coatings: Enteric coating for delayed release
This composition ensures the capsule's structural integrity, ease of digestion, and targeted drug delivery.
Applications of Capsules in Medicine
Capsules are used to deliver:
- Prescription medications (e.g., antibiotics)
- Over-the-counter (OTC) drugs (e.g., ibuprofen)
- Supplements and herbal remedies
- Oils, extracts, and probiotics
Capsules are preferred for:
- Fast release
- Accurate dosing
- Taste masking
- Custom compounding in pharmacies
Example: Amoxicillin 500 mg commonly uses size 0 capsule.
FAQs About Capsule Sizes and Usage
- How much powder fits in a Size 0 capsule?
Approximately 400–500 mg, depending on bulk density.
- Which capsule size is best for 500 mg?
Size 0 or 00.
- Are softgel and hard capsules interchangeable?
No. Softgels are used for oils/liquids, while hard capsules are for dry powders.
- How fast do gelatin capsules dissolve?
Usually within 5–30 minutes in the stomach.
- Are there vegan capsules?
Yes, made from HPMC or pullulan, free from animal derivatives.
Capsule Filling Machines:
If you're producing capsules in-house or at scale, capsule filling machines become essential. These machines automate the process of aligning, filling, and closing capsules with high speed and accuracy. They're available in:
- Semi-automatic Capsule Filling Machine for mid-size batches
- Fully automatic Capsule Filling Machine for industrial use
Interested in capsule machines? Learn more about LTPM CHINA’s pharmaceutical-grade capsule filling equipment.
Conclusion
Understanding capsule sizes helps optimize formulation, ensure dosage accuracy, and enhance patient compliance. Whether you're filling 60 mg or 1000 mg, choosing the right capsule size and shell material is critical. Use standard size charts and pharmaceutical guidelines for best results.
Always consider the active ingredient’s bulk density, target user group, and processing needs. When scaling up, a suitable capsule filling solution is just as important as the capsule itself.