Solubility Of drugs

1. SOLUBILITY(METHODS THAT
ENHANCE SOLUBILITY)

2. INTRODUCTION

3. COSOLVENCY
The mechanism by which cosolvency enhances solubility depends on
several factors including;
1) increasing the solvation power of the solvent: the addition of the
cosolvent Can increase the solvationpower of the original solvent
which can help solubilize the solute. This occurs because the
cosolvent molecules can surround the solute molecules effectively,
reducing the intermolecular forces between them and allowing them
to dissolve more easily.

4. 2) Changing the properties of the solvent : the addition of the
cosolvent Can change the properties ofthe original solvent such as
polarity or hydrogen bonding capacity which helps to solubilize the
solvent.
3): Reducing the interfacial tension: a cosolvent Can reduce the
interfacial tension between the solute and solvent molecules which
can help to dispense the solute particles and increase the solubility
solute. For example, if a solute is insoluble in water, and tend to form
larger aggravates or clusters, the addition of a cosolvent such as
surfactants can help reduce the interfacial tension and dispense the
solute particles increasing there solubility.

5. 4) Reducing the precipitation of the solute: the presence of the
colsovency can reduce the precipitationof the solute by shifting the
solubility equilibrium towards the dissolved state.
5) Increasing the solvecy power of the solvent system: a cosolvent
Can increase the solvency power of asolvent system, which can help
dissolve a solute that is not soluble in a single solvent. for example, if
a solute is hydrophobic, and not soluble in water the addition of a
colsovent such as propylene glycol which is a good solvent for many
hydrophobic compounds, Can increase the solvency power of solvent
system and enhance the solubility of the solute. Propylene glycol is a
clear, colorless and odorless liquid
that is miscible with water and many organic solvents, it commonly
used as a cosolvent in Pharmaceutical formulations to enhance the
solubility of poorly soluble drugs.

6. 6) Disrupting the solute -solute interactions: a cosolvency can
disrupt the attractive forces betweensolute molecules, which can
help to increase the solubility of the solute. For example, a solute
forms a
crystalline structure that reduces it's solubility. The Addition of a
cosolvent such as glycerin which can disrupt the crystalline
formation Can help increase the solubility of the solute.
Example of a drug that has been shown to be beneficial from
cosolvency is cyclosporine which is an immunal suppressive egent
used to prevent organ rejection in transplant patients.
Cyclosporine is poorly soluble in water which limits it's
bioavailability. However, the addition of a cosolvent such as
polyethylene glycol has been shown to increase the solubility and

7. Cosolvency is the useful technique for improving the solubility and
bioavailability of poorly soluble drugs in Pharmaceuticals by
adding a cosolvent to a primary solvent.
CONCLUSION

10. REFERENCES