The partition coefficient is a ratio that measures a substance's relative solubility in lipid and aqueous phases. It is calculated as the concentration of a solute in the lipid or organic phase divided by its concentration in the water or aqueous phase. A partition coefficient greater than 1 indicates a lipophilic substance that is more soluble in lipids, while a value less than 1 represents a hydrophilic substance that is more soluble in water. Octanol is commonly used as the non-aqueous phase and water as the aqueous phase when experimentally determining drug partition coefficients, which affect processes like solubility, administration route, absorption, distribution, and elimination.

1. Partition Coefficient
Lipophilicity & Hydrophilicity

2. Lipophilic substance: It is substance that attract to lipde
may be soluble or adsorbed.
Hydrophilic substance : It is substance that attract to
water may be soluble or adsorbed.

3. Partition Coefficient: It is the ratio of lipophilicity to
hydrophilicity of solute between immiscible phases
partition coefficient or distribution coefficient: defined as
the ratio of the solubility in the non-aqueous (oily) phase,
Co , to that in the aqueous phase, Cw.

4. P = Co /Cw
P: Partition Coefficient
Co: Solute conc in lipid or organic phase
Cw: Solute conc in water or aqueous phase
If P > 1 the solute is lipophilic so not soluble in water
If P < 1 the solute is hydrophilic so soluble in water
If P = 1 the solute is amphiphilic so mybe soluble in
both water or oil

5. - Octanol or N-octanol is usually used as the
non-aqueous phase in experiments to measure
the partition coefficient of drugs.
-Other non-aqueous solvents, for example
isobutanol and hexane, have also been used.
- Water is usually used as the aqueous phase in
experiments to measure the partition
coefficient of drugs

6. Partition Coefficient (Lipophilicity & Hydrophilicity)
Affecting on
1- Pre formalion (solubility)
2- Rout of administration
3- Absorption
4- Distribution
5- Eilmination