Geometric dilution is a pharmaceutical process that thoroughly mixes a small amount of a drug with an appropriate amount of a diluent, an inert substance that thins or binds the drug. It ensures equal distribution of the drug throughout the resulting compound, according to the UNC Eshelman School of Pharmacy.
The method used depends on the types of substances used, such as a fluid or powder, and the form, such as an ointment or tablet, of the compound. Two commonly used geometric dilution methods include trituration, which can be used to combine powders or mix a powder into an ointment, and the liquid aliquot method, which involves combining fluids to create a solution, as explained by the UNC Eshelman School of Pharmacy.
Trituration, which involves reducing a substance to particle size, requires the use of a mortar and pestle to grind together equal parts of substances in small-batch quantities, adding the same amount of each substance and repeating the process until the entire amount of both substances has been mixed together. The liquid aliquot method involves dissolving a quantity of the drug in a small quantity of an appropriate solvent, often water or alcohol, to reach a desired volume, according to the UNC Eshelman School of Pharmacy. The aliquot, which is the desired amount of the concentrated drug solution, is then added to a larger amount of solution to make up the total volume of the prescription.