Solutions, Suspensions, and Emulsions Practicum in Pharmacy

Introduction Liquid compounds are probably the most commonly prepared compounds in a pharmacy. Liquids can be administered by mouth, topically, rectally, vaginally, and in the eyes or ears.

Composition and Ingredients There are several factors that have to be considered when preparing any oral liquid: Drug Concentration Solubility pH Taste Stability

Types and Definitions Solutions – clear liquid preparations in which all the ingredients are dissolved in a suitable vehicle and contain one or more active ingredients. Five Types of Solutions: Oral Liquid Solutions – taken by mouth Topical Solutions – applied to the skin Syrups – concentrated sugar aqueous liquids Elixirs – sweetened and alcohol based Aromatic Waters – clear, saturated aqueous solutions of volatile oils or aromatic substances and may be used internally or externally.

Composition and Ingredients Solutions Solubility – that is how many milligrams of the drug will dissolve in a specific number of milliliters of a vehicle. Remember to mix like products Flavorings and sweeteners can be added to the preparations to hide bitter taste or odor. Preservatives can be added to prevent microbial growth. Buffers can be added to maintain the pH for stability.

Preparation and Compounding Techniques Solutions Solutions are one of the easiest and most common liquids to compound. Most water soluble ingredients will dissolve in water by simply stirring, shaking, or allowing time to dissolve on their own. If the solution is concentrated, heat may be needed to dissolve the ingredients. Others may need a high degree of agitation, such as a blender.

Preparation and Compounding Techniques Elixirs co-solvent system – two ingredients together used as a solvent. Elixirs have a water component and an alcohol component as the vehicle. When preparing an elixir, the alcohol-soluble ingredients should be mixed with ethanol and the water-soluble ingredients should be dissolved in water prior to mixing the two components together.

Types and Definitions Suspensions – liquids that contains ingredients that are not soluble in their vehicle, but rather suspended or re-suspended upon shaking. They are two-phased systems consisting of fine solid particles dispersed in liquid. Can be taken by mouth or applied topically.

Composition and Ingredients Suspensions Suspensions can be made from the same vehicles used to prepare solutions. Fixed oils, including vegetable oils such as almond oil, corn oil, or peanut oil, may be used as a suspending agent for some insoluble drugs.

Preparation and Compounding Techniques Suspensions The first step in compounding a suspension is to reduce the particle size of the solid component. Grind with a mortar and pestle, pass through a mesh sieve, using a machine similar to a coffee grinder, or a tablet pulverizer attachment to a blender. Next, the powder should be wetted prior to mixing with the primary vehile. Hydrophilic – add a little water and mix until a paste is formed Hydrophobic – add a little glycerin and mix until a paste is formed Slowly add the vehicle to the thick paste while constantly stirring.

Types and Definitions Emulsions –is a type of suspension consisting of two immiscible liquids and an emulsifying agent to hold them together. 2 Types of Emulsions: Water-in-Oil (w/o) – occlusive, greasy, not water washable Oil-in-Water (o/w) – water washable, hydrophilic, nonocclusive, and nongreasy.

Composition and Ingredients Emulsions Emulsions contain three basic components: A Lipid or Oil Phase An Aqueous Phase Emulsifier - chemical additives that encourage the suspension of one liquid in another

Preparation and Compounding Techniques Emulsions Emulsions are more complicated to prepare. Preparing emulsions requires an energy source that will break up the oil and water liquids to increase the surface area of the internal phase. Methods used to prepare emulsions: English Method – also called the wet gum method. A mucilage (sticky mixture) is prepared by adding a small quantity of water to the gum and then triturated or mixed until the mixture is uniform. The oil component is added in small quantities by using rapid trituration, resulting in a thick, viscous mixture. More water is slowly added and the mixture is rapidly triturated until the emulsion is formed.

Preparation and Compounding Techniques Emulsions Methods used to prepare emulsions: English Method – also called the wet gum method. A mucilage (sticky mixture) is prepared by adding a small quantity of water to the gum and then triturated or mixed until the mixture is uniform. The oil component is added in small quantities by using rapid trituration, resulting in a thick, viscous mixture. More water is slowly added and the mixture is rapidly triturated until the emulsion is formed 2. Continental Method – also called the dry gum method. The gum is rapidly mixed with oil, and then the water is added all at once with rapid trituration. When a snapping sound is heard, the primary emulsion has formed. 3. Bottle Shaking Method 4. Beaker Method – involves using synthetic emulsifying agents and heating.