Essential Composition of Pills.
—A pill mass consists of at least two parts: active ingredient and excipient. The active ingredient suitable for pill form is almost any solid medicine that is not deliquescent and the dose of which is small (not exceeding 1 Gm.). If the dose is higher than 0.5 Gm., two pills should be made of it. Even deliquescent substances may be prescribed if their dose is very small. Liquids can be prescribed in pill form, if the dose of the liquid does not exceed a drop.A diluent is necessary when the dose of the active ingredient is very small, as 1 mg. of strychnine sulphate. Here the diluent (starch) is required to form pills of the proper size. Very irritant or caustic substances require a diluent in order to avoid excessive action on the stomach. Liquids and deliquescent bodies need an absorbent powder, such as kaolin.
FANTUS B. THE TECHNIC OF MEDICATIONA SERIES OF ARTICLES ON THE METHODS OF PRESCRIBING AND PREPARING, THE INDICATIONS FOR, AND THE USES OF VARIOUS MEDICAMENTS. JAMA. 1926;86(15):1129–1131. doi:10.1001/jama.1926.26720410004011