Solid Dosage Form – Capsule
A lubricant is added to the active compound to facilitate the flow of the drug-fill into the encapsulating machinery. The use of lubricant is especially important when an automatic capsule filling machine is utilized. Magnesium stearate (frequently less than 1%) is commonly used as a lubricant in capsule and tablet making.
- Wetting Agent
Wetting agents are used to enhance the dissolution of solid particles. Lithium carbonate is a commonly used wetting agent. Wetting agent pre-vents agglomeration of particles and accelerates the dissolution of particles by allowing water to penetrate and replace air between particles.
Soft Gelatin Capsule
Soft gelatin (also called softgel) capsules consist of one-piece hermetically-sealed soft shells. Soft gelatin capsules are prepared by adding a plasticizer, such as glycerin or polyhydric alcohol (e.g., sorbitol), to gelatin. The plasticizer makes gelatin elastic. Soft gelatin capsules come in various shapes such as spherical, elliptical, oblong, and special tube shapes with and without twist off. They can contain non-aqueous liquids, suspensions, pasty materials, or dry powders. They are especially important to contain volatile drug substances or drug materials susceptible to deterioration in the presence of air.
Excipients of Softgels
- Softener (plasticizer): sorbitol, xylose, maltitol, glycerin, PEG, water)
- Preservatives (methyl paraben, propyl paraben, butylated hy-droxyaniline, EDTA, sodium benzoate)
- Dyes, pigments,
- Solvent – Polar: glycerin, PEG, PEG 400, PEG 3350, ethanol, PPG, water, Nonpolar: beeswax, coconut oil, triglycerin, corn oil, mineral oil, soybean oil, D,L-α-tocopherol
- pH-adjusting additive
- Flavor and fragrance
- Pigment: titanium oxide, ferric oxide
- Anticaking agent: Silicone dioxide
- Humectant: polyol
Important Factors in Soft Gelatin Capsule Decision
- Organic solubility – Common organic solvents: DMSO. Acceptable softgel excipients: fatty liquids, PEGs, propylene glycol, surfactants
- Drug-excipient compatibility – Chemical stability. Physical stability: Drug migration into shell, gelatin disintegration, recrystallization of gelatin