Question

Which of the following is not a method for solubility enhancement:

• A. Crystallization
• B. Co-solvency
• C. Salt formation
• D. Hydrotropy

Answer 1

The Correct Option is A

The correct option is (A): Crystallization.

Answer 2

The question asks which listed technique is not actually used to increase how soluble a poorly water-soluble drug is. Let's check what each option genuinely does to a drug's solubility.

1. Crystallization: Crystallization is a purification and particle-formation technique used to isolate a solid compound in a defined crystal form. By itself it does not add anything to the system that increases how much drug can dissolve, so it is not classified as a solubility enhancement method.
2. Co-solvency: Adding a water-miscible solvent alongside water lowers the overall polarity of the solvent system, which lets poorly water-soluble drugs dissolve to a much greater extent, making this a genuine and widely used solubility enhancement technique.
3. Salt formation: Converting a weakly acidic or basic drug into its salt form changes its ionization and crystal lattice energy, generally giving much higher aqueous solubility than the parent free acid or base, so this is also a recognized solubility enhancement method.
4. Hydrotropy: Adding a hydrotropic agent in high concentration increases the solubility of a poorly soluble compound by disrupting the structure of water around the drug molecules, another established technique for boosting solubility.

Only crystallization works in the reverse direction, taking dissolved drug out of solution rather than helping more of it dissolve.

The correct answer is Crystallization.