Ointments are mixtures of a fatty vehicle with which medicinal agents are incorporated, readily fusing at the body-temperature, 35 to 40C. (95o to 104o F.).

The medicinal ingredients must be minutely distributed through the vehicle in order that the ointment may not prove irritating, and that the greatest possible surface be presented to the epidermis 9 with a view to quick and uniform absorption. For this reason the highest quality of an ointment (next to its proper melting-point) is smoothness. In the preparation of ointments care must therefore be taken that the method employed be such as to yield smooth products.

The melting-point is governed by the fusibility of the vehicle used, which is either officially directed, as in official preparations, or in extemporaneous preparations prescribed by the physician.

The official Ointments are prepared (1) by mechanical admixture, (2) by fusion, or (3) by chemical reaction.

Mixing the medicinal substances with the fatty body in a mortar or on a slab is the process usually employed for solid substances, especially when insoluble in the fat. Powdered drugs, acids, alkaloids, extracts, and salts (not attended by chemical union) are examples adapted to this process.

The following points must be observed:

Solids must be in a fine powder before being incorporated with the vehicle; sometimes it is an advantage to triturate the solid with a small quantity of a bland fixed oil, as Almond Oil or Olive Oil, into a smooth cream before it is mixed with the vehicle proper-Lard, etc.

Extracts should be reduced to a semi-liquid condition by trituration with a little dilute Alcohol or Water. Substances soluble in fats, such as Carbolic Acid, Iodine, and Camphor, may be dissolved directly in the fat by the aid of a gentle heat.

The following are the official Ointments, with their drug-strengths, their respective vehicles being given in parentheses: