1. A semisolid preparation usually containing medicinal substances and intended for external application. Ointment bases used as vehicles fall into four general classes: 1) hydrocarbon bases (oleaginous ointment bases) keep medicaments in prolonged contact with the skin, act as occlusive dressings, and are used chiefly for emollient effects; 2) absorption bases either permit the incorporation of aqueous solutions with the formation of a water-in-oil emulsion or are water-in-oil emulsions that permit the incorporation of additional quantities of aqueous solutions; such bases permit better absorption of some medicaments and are useful as emollients; 3) water-removable bases (creams) are oil-in-water emulsions containing petrolatum, anhydrous lanolin, or waxes; they may be washed from the skin with water and are thus more acceptable for cosmetic reasons; they favor absorption of serous discharges in dermatologic conditions; and 4) water-soluble bases (greaseless ointment bases) contain only water-soluble substances.
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