Capsules
8 minute read
What you will learn
- Define a capsule and name the main types
- Compare hard and soft gelatin capsules
- State how capsule sizes are numbered and how the right size is chosen
- List the advantages and disadvantages of capsules
- Describe how a hard capsule is filled in small quantities
- Explain how capsules are packaged, stored and swallowed
Key points
- A capsule is a solid dosage form where the drug is enclosed in a soluble shell, usually made of gelatin.
- Hard capsules have two pieces (cap and body) and hold powders or granules. Soft capsules are one sealed piece and hold oils and liquids.
- Hard capsule sizes run from 000 (largest) to 5 (smallest).
- Size is chosen by the volume the dose takes up, not its weight.
- Gelatin is sensitive to heat and moisture, so capsules must be stored cool and dry.
- Capsules mask taste and are easy to swallow, but they cannot hold water-based liquids in a hard shell.
What is a capsule?
A capsule is a solid dosage form in which the drug is enclosed in a small shell that dissolves in the stomach. The shell is usually made of gelatin. Once the shell dissolves, the contents are released.
Types of capsule
| Type | Description | What it holds |
|---|---|---|
| Hard gelatin capsule | Two pieces: a body and a cap that slides over it | Dry powders, granules, pellets |
| Soft gelatin capsule | One sealed piece with a flexible, thicker shell | Oils, liquids, suspensions (for example, some vitamin and cod liver oil capsules) |
| Enteric-coated capsule | Capsule or contents coated to resist stomach acid | Drugs that must be released in the intestine |
| Vegetarian capsule | Shell made from plant material (such as cellulose) instead of gelatin | Powders and granules, for patients who avoid animal products |
Gelatin comes from animal sources. Some patients avoid it for religious or personal reasons, so plant-based capsules are useful alternatives to know about.
Capsule sizes
Hard capsules come in numbered sizes. The numbering can seem backwards:
- 000 is the largest
- then 00, 0, 1, 2, 3, 4
- 5 is the smallest
The largest holds about 1.4 mL and the smallest about 0.13 mL.
Choosing a size: the right size depends on the volume the dose takes up, not on its weight. A light, fluffy powder takes up more room than a dense powder of the same weight, so it needs a bigger capsule.
Advantages and disadvantages
Advantages
- They hide the taste and smell of the drug.
- The shell is smooth and slippery, so capsules are easy to swallow.
- The shell dissolves quickly, so the drug is released quickly.
- They can hold powders, oils and other liquids.
- Opaque shells protect light-sensitive drugs.
- Small numbers can be filled by hand in the pharmacy.
Disadvantages
- Gelatin is damaged by heat and moisture.
- A hard capsule cannot hold a water-based liquid, because the water dissolves the shell.
- Very soluble drugs that irritate the stomach can cause problems, because the drug is released all at once in one spot.
- Capsules cannot be divided for a smaller dose.
- More expensive than tablets.
Capsules compared with tablets
| Capsule | Tablet | |
|---|---|---|
| Form | Drug inside a shell | Compressed solid |
| Taste masking | Very good | Needs coating |
| Can hold liquids | Yes (soft capsules) | No |
| Sensitive to humidity | Very | Less so |
| Can be divided | No | Some can (scored tablets) |
Filling hard capsules by hand
On a small scale, hard capsules are filled in the pharmacy:
- Pull the cap off each capsule and place the bodies in a holder or tray.
- Weigh the correct amount of powder and make sure it is well mixed.
- Fill each body with the powder. Pressing the body into a layer of powder (the punch method) packs it in. Use a spatula to fill any remaining space.
- Replace each cap and press until it clicks shut.
- Wipe the capsules clean and check them.
- Pack and label.
In industry, capsule-filling machines do the same job at high speed.
Packaging and storage
- Pack capsules in blister packs or tightly closed bottles with a drying agent if needed.
- Store in a cool, dry place. In hot, humid conditions gelatin shells become soft, sticky and misshapen.
- Do not store in a bathroom or a hot vehicle.
- Keep the container tightly closed, and always check the expiry date.
Helping patients take capsules correctly
- Sit or stand upright.
- Swallow the capsule whole with a full glass of water. Do not take it dry, as it can stick in the food pipe.
- Do not open or chew a capsule unless the label says to.
- Keep out of reach of children.
Exam focus
- Know which capsule size is the largest (000) and which is the smallest (5).
- Hard gelatin capsules: powders and granules. Soft gelatin capsules: oils and liquids.
- Storage questions: gelatin softens and sticks in heat and humidity.
- Common mistake: thinking a larger size number means a larger capsule. It is the opposite: 5 is the smallest and 000 is the largest.
Quick check
Test yourself before you move on. Pick an answer to see the explanation.
1.Which is the largest hard capsule size?
2.Soft gelatin capsules are best suited for:
3.Why should capsules be kept away from heat and humidity?
4.The size of capsule used for a dose is chosen mainly by:
5.A hard gelatin capsule is made up of: