The Pharmaceutics and Compounding Laboratory
Pharmaceutical Solutions I:
Simple, Saturated, Syrups

Syrups

Because of their prevalence as solution vehicles, we will consider some of the special qualities of syrups. A syrup is a concentrated or nearly saturated solution of sucrose in water. A simple syrup contains only sucrose and purified water (e.g. Syrup USP). Syrups containing pleasantly flavored substances are known as flavoring syrups (e.g. Cherry Syrup, Acacia Syrup, etc.). Medicinal syrups are those to which therapeutic compounds have been added (e.g. Guaifenesin Syrup).

Syrup, USP contains 850 gm sucrose and 450 ml of water in each liter of syrup. Although very concentrated, the solution is not saturated. Since 1 gm sucrose dissolves in 0.5 ml water, only 425 ml of water would be required to dissolve 850 gm sucrose. This slight excess of water enhances the syrup's stability over a range of temperatures, permitting cold storage without crystallization.

The high solubility of sucrose indicates a high degree of hydration or hydrogen bonding between sucrose and water. This association limits the further association between water and additional solutes. Hence, syrups have a lower solvent power than water and "salting out" (see Remington's for explanation) may be a problem.