The tablet or capsule is the most commonly used oral dosage form, but is also often the most complex to make. The process of making capsules involves compressing the herb, which results in a reduction in effective surface area. The herb starts out as a very fine powder, but then is compressed into a single dosage unit. Certain capsule ingredients are included to add various physical properties to the therapeutic properties of the herb.
Ingredients of the common herbal supplement include the drug, which may be poorly soluble, or hydrophobic. A Lubricant is usually quite hydrophobic. Granulating agents may be used which tend to help the ingredients adhere to one another. Filler maybe included and could interact with the drug; it should be water-soluble. Wetting agents are also sometimes added to help water penetrate into the capsule. Disintegration agents (if included) help to break the capsule apart after ingestion.
Coated tablets or capsules are used to help mask unpleasant tastes, protect capsule ingredients during storage, or simply improve the appearance of the capsule. This barrier must break down quickly, or it may hinder the drug's bio-availability. Some capsules are treated with enteric coatings, meaning that they are coated with a material that will dissolve in the intestine, but remain intact in the stomach. Polymeric acid compounds have been used for this purpose with some success.