Capsules are commonly used in people's daily lives. The main capsular material of the empty capsule is gelatin. Because of its unique structure and dissociation of anion and cation on the molecular chain, medicinal gelatin has good solubility and water retention. However, not all medicines can be made into capsule preparations. The following are the following drugs that are not suitable for capsule preparation:
(1) The aqueous solution and the dilute alcohol solution can soften and dissolve the capsule, so that they cannot be made into a capsule.
(2) Medicines which are easily soluble, or small doses of stimulating drugs, because the local concentration of the capsule shell is too high to stimulate the stomach, are not suitable for capsules.
(3) The easily weathered medicine can make the shell soft and the hygroscopic drug can make the shell brittle, so they are not suitable to make a capsule.
(4) Strong acid drugs can cause hydrolysis of the capsule shell, and strong alkaline drugs can cause the capsule to decompose and affect disintegration, so it is not suitable for capsule preparation.