Substances that dissociate into 3 ions: 2.6 Substances that dissociate into 4 ions: 3.4 Substances that dissociate into 5 ions: 4.2 Adjusting the Isotonicity of Hypotonic Solutions: Example: How much sodium chloride is required to render 100 ml of a 1% solution of apomorphine hydrochloride isotonic with serum? Solution: From the previous table, it is found that a 1% solution of the drug has a freezing point lowering of 0.08⁰C. To make this solution isotonic with blood, sufficient sodium chloride must be added to reduce the freezing point by an additional 0.44⁰C (0.52 - 0.08). In the freezing point table, it is also observed that a 1% solution of sodium chloride has a freezing point lowering of 0.58. By the method of proportion, Thus 0.76% sodium chloride will lower the freezing point the required 0.44o and will render the solution isotonic. The solution prepared by dissolving 1.0 g of apomorphine hydrochloride and 0.76 g of sodium chloride in sufficient water to make 100 ml of solution. Sodium Chloride Equivalent Method: The sodium chloride equivalent, of a drug is the amount of sodium chloride that has the same Osmotic effect as 1 gram of the drug. The sodium chloride equivalents E for a number of drugs are listed in the previous table. Calculations for determining the amount of sodium chloride or other inert substance to render a solution isotonic simply involve: Multiplying the quantity of each drug in the prescription by its sodium chloride equivalent. Calculating the amount of sodium chloride that renders the whole prescription volume isotonic. Subtract the value in step (a) from that in step b give the amount of sodium chloride must be added. If the isotonicity is to be adjusted with some other inert substance the calculated NaCl amount in the previous step is converted to the inert substance using its NaCl equivalent value. Example:
Substances that dissociate into 3 ions: 2.6 Substances that dissociate into 4 ions: 3.4 Substances that dissociate into 5 ions: 4.2 Adjusting the Isotonicity of Hypotonic Solutions: Example: How much sodium chloride is required to render 100 ml of a 1% solution of apomorphine hydrochloride isotonic with serum? Solution: From the previous table, it is found that a 1% solution of the drug has a freezing point lowering of 0.08⁰C. To make this solution isotonic with blood, sufficient sodium chloride must be added to reduce the freezing point by an additional 0.44⁰C (0.52 - 0.08). In the freezing point table, it is also observed that a 1% solution of sodium chloride has a freezing point lowering of 0.58. By the method of proportion, Thus 0.76% sodium chloride will lower the freezing point the required 0.44o and will render the solution isotonic. The solution prepared by dissolving 1.0 g of apomorphine hydrochloride and 0.76 g of sodium chloride in sufficient water to make 100 ml of solution. Sodium Chloride Equivalent Method: The sodium chloride equivalent, of a drug is the amount of sodium chloride that has the same Osmotic effect as 1 gram of the drug. The sodium chloride equivalents E for a number of drugs are listed in the previous table. Calculations for determining the amount of sodium chloride or other inert substance to render a solution isotonic simply involve: Multiplying the quantity of each drug in the prescription by its sodium chloride equivalent. Calculating the amount of sodium chloride that renders the whole prescription volume isotonic. Subtract the value in step (a) from that in step b give the amount of sodium chloride must be added. If the isotonicity is to be adjusted with some other inert substance the calculated NaCl amount in the previous step is converted to the inert substance using its NaCl equivalent value. Example:
isotonic_solutions.docx