pKa (pKa)

pKa

Chemistry

The negative logarithm of the acid dissociation constant (Ka), representing the pH at which a drug molecule is 50% ionized and 50% un-ionized. pKa is a fundamental physicochemical property that determines a drug's ionization state at physiological pH, directly influencing its solubility, membrane permeability, absorption, distribution, and protein binding behavior.

Exemples

Aspirin (pKa 3.5): predominantly un-ionized in stomach acid (pH 1-2), favoring gastric absorption
Diazepam (pKa 3.3): un-ionized at physiological pH, high membrane permeability
Morphine (pKa 8.0): mostly ionized at pH 7.4, ion trapping in acidic compartments

Le saviez-vous ?

The negative logarithm of the acid dissociation constant (Ka), representing the pH at which a drug molecule is 50% ionized and 50% un-ionized. pKa is a fundamental physicochemical property that …