Syrups are concentrated, aqueous preparations of a sugar or sugar substitutes with or without flavoring agents and medicinal substances.

Syrups containing flavoring agents but not medicinal substances are called flavored vehicles/syrups, for example, cherry syrup, cocoa syrup. Syrups containing medicinal agents are called medicated syrups, for example, chlorpheniramine maleate syrup. Most syrups contain the following components in addition to purified water and any medicinal agents:

1. Sugar, usually sucrose or sugar substitutes that are used to provide sweetness and viscosity
2. Antimicrobial preservatives
3. Flavors
4. Colorants

Sucrose is most frequently employed in syrups, but sometimes it may be replaced by other sugars such as dextrose or nonsugars such as sorbitol, glycerin and propylene glycol. Syrup imparts a characteristic viscosity; along with the sweetness and flavors, it results in a type of pharmaceutical preparation that is effective in masking the taste of the added medicinal agents. When the syrup is swallowed, only a portion of the dissolved drug actually makes contact with the taste buds, the remainder of the drug being carried down the throat in the containment of the viscous syrup. The thick sweet syrup has a soothing effect on the irritated tissues of the throat as it passes over them. Simple syrup I.P. contains 66.7% w/w sucrose. At this concentration, the syrup is resistant to microbial growth, due to the unavailability of the water required for the growth of microorganisms. Under cool storage conditions, some sucrose might crystallize from the solution when the syrup is completely saturated with sucrose. This can be prevented by the addition of sorbitol in the preparation, which would prevent recrystallization of the excess sugar from the supersaturated sugar solution during normal storage conditions.