Question

CLASS-II method for tonicity adjustment is:

• A. Cryoscopic
• B. NaCl Equivalent
• C. White Vincent
• D. Mole fraction

Hint:

White Vincent method is especially useful in hospital and extemporaneous formulations to make isotonic solutions accurately without prior measurement of final volume.

Answer 1

The Correct Option is C

Tonicity adjustment is a critical step in pharmaceutical formulations, especially for parenteral, ophthalmic, and nasal preparations. The White Vincent method is categorized under Class II methods of tonicity adjustment. Class II methods are used when the volume of the solution needs to be adjusted after the addition of the drug. The White Vincent method calculates the volume of isotonic solution to be prepared by using the sodium chloride equivalent (E-value) of the drug. White Vincent Formula: \[ V = \frac{w \times E \times 111.1}{0.9} \] Where: - \( V \) = volume of isotonic solution (in mL)
- \( w \) = weight of drug (in grams)
- \( E \) = NaCl equivalent value of the drug
- 0.9 = concentration of normal saline (in %)
- 111.1 = volume (in mL) that 0.9 g NaCl will make isotonic
Explanation of options: - (a) Cryoscopic: Class I method based on freezing point depression.
- (b) NaCl Equivalent: Concept used in several methods but not a method itself.
- (c) White Vincent: Correct. It is a Class II method.
- (d) Mole fraction: Not commonly used for tonicity adjustments in practical pharmaceutics.