JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD Pharm. D I Year PHARMACEUTICS Previous Question Paper (February/March - 2023 - R08)

The method of alligation is a mathematical technique used to calculate the proportions in which two or more substances of different concentrations must be mixed to obtain a desired concentration. It relies on the principle that the loss in concentration of the stronger solution is equal to the gain in concentration of the weaker solution. The calculation involves placing the desired concentration in the center and subtracting it from the given concentrations to determine the parts of each required.

The geometric dilution method is a technique used for the uniform incorporation of a small quantity of a potent drug into a large quantity of a diluent. The principle involves mixing the potent drug with an equal volume of the diluent, then adding an equal volume of diluent to the mixture, and repeating this process until all ingredients are incorporated. This ensures a homogeneous distribution of the drug throughout the final product.

The methods for adjusting the isotonicity of pharmaceutical solutions include the Class I methods (Cryoscopic method and Sodium Chloride Equivalent method) and Class II methods (White-Vincent method and Sprowls method).

Advantages of these methods include ensuring patient comfort upon administration, preventing tissue irritation, and maintaining the stability and therapeutic efficacy of ophthalmic or parenteral preparations.

The Sodium Chloride Equivalent (E-value) method is a Class I method where the amount of sodium chloride required to make a solution isotonic is calculated. The E-value represents the weight of sodium chloride that is osmotically equivalent to 1 gram of the drug. The formula used is:

Where W is the weight of sodium chloride in grams to be added, V is the volume of the solution in milliliters, E is the sodium chloride equivalent of the drug, and C is the concentration of the drug in grams per milliliter. By adding the calculated amount of sodium chloride, the solution is rendered isotonic with body fluids.