Capsules Flashcards
Capsule
a solid dosage form in which medicinal agents and/or inert substances are enclosed in a small shell of gelatin
Gelatin
protein obtained by partial hydrolysis of collagen derived form bovine or porcine skin and bone
- Derived from skin, has plasticity
- Derived from bone, has firmness
Bloom strength should be approximately 150-280g
- Stable in air when dry, but is subject to microbial decomposition when it becomes moist
Non-animal derived alternatives of gelatin
Hydroxypropyl methylcellulose, starch and carrgeenan capsules
Advantages of capsules
- Can be used to deliver powders, granules, beads and prefabricated tablets, semisolids and liquids that do not dissolve gelatin
- Can mask taste and odor of drug
- Are easy to swallow
- Generating, rate of drug absorption after oral administration : Capsule > tablet
- Can be administered orally, rectally and vaginally
Disadvantages of capsules
- Sensitive to relative humidity
- Not suitable for liquids that dissolve gelatin
- Some can be tampered with
Plasticizers
Reduce rigidity of gelatin, making it more pliable
Ex: Water, Sorbital and propylene glycol
Preservatives
Reduce bacterial and fungal growth
Ex: Methylparaben and propylparaben
Colorants
Change color
Ex: Azo and xanthene dyes and iron oxide pigments
Opacifiers
Makes clear gelatin opaque, which can protect contents from light
Ex: Titanium dioxide
Hard gelatin capsules
Made of gelatin, sugar and water, and may contain colorants, opaquants
and preservatives
Shells normally have moisture content of 13-16%
– If too dry it becomes brittle
– If too moist it becomes soft and sticky
Hard gelatin capsules are made how
Manufactured in two parts:
- Capsule body
- Shorter cap
Produced by mechanical dipping and then spinning of pins or pegs into a
temperature-controlled (50 C) reservoir of melted gelatin mixture
The two parts overlap when joined, with the cap fitting snugly over the open end of
the capsule body
Hard gelatin capsule sizes
Various sizes: 000 (largest) to 5 (smallest) for human use
- Largest size capsules carry more weight of drug
Capsule sizes
- Capsules can be used to encapsulate between 65 and 1000 mg of powdered material
- Some patients have difficulty swallowing larger capsules
-Some patients find smaller capsules hard to handle - If the active drug powder is large, the total amount can be divided into two smaller
capsules that are easier to swallow - If the active drug powder is small, more diluent can be added to increase the size of a
capsule for handling convenience
Rule of sizes
When the bulk density of powders is between 0.4 and 0.8 g/mL w an average of 0.6 g/mL, the size of the capsule can be approximated by the rule of sixes
- Each grain is equivalent to 0.065 g or 65 mg
Number 6 - Capsule size = weight of powder in grains
For example 6 - Capsule size 1 is 5. So 5 grains = 325 mg of powdered drug can be filled in capsule size #1
Rule of sevens
- Convert weight of powder per capsule to grains (1 grain = 0.065 g);
- subtract the number of grains from 7; and
- match the result to the following list
Resulting number Capsule Size
-3 000
-2 00
-1 or 0 0
1 1
2 2
Method does not work if the resulting number is higher than 5 or lower than -3
Preparation of hard gelatin capsules
- developing and preparing the formulation and selecting capsule size
- filling the capsule shells
- capsule sealing (optional)
- cleaning and polishing the filled capsules