drug ionization and absorption. Basic drugs, which are typically ionized in the acidic environment of the stomach (pH around 1.5 to 3.5), can
pH = pKa log [ionized drug]/[un-ionized drug]. For basic compounds: pH Percentage ionisation of weakly acidic and weakly basic drugs as a function of pH.
How does ionization constant affect the bioavailability of drugs. Ionized drugs are not absorbed as efficiently as un-ionized drugs are. New cards. 6. How
by FYS Kong 2024 Cited by 70For example, azithromycin has a pKa of ∼8.5,19 meaning that 50% of the drug is ionized and 50% is un-ionized at a pH of 8.5. Only the un-ionized
Ionization coefficient is the pH at which the drug is 50% ionized and 50 % unionized. For acidic drugs, pKa is lower, while that for basic drugs
Unionized drugs penetrate biological membranes more EASILY than ionized drugs. Unionized drugs are more lipid soluble. Charges on biological membranes bind or repel ionized drugs. Ionized drugs associate with water molecules, creating larger particles with reduced penetrating capability.
The third step involved developing a combined equation that includes neutral and ionized species and the fraction ionized for all drugs. Equation 11 includes terms for unionized species (neutral drugs and the unionized fractions of acids and bases), and the ionized forms of acids and bases.
Finally, using the Henderson-Hasselbalch equation, and knowing the drug's (pH at which there is an equilibrium between its ionized and non-ionized molecules), it is possible to calculate the non-ionized concentration of the drug and therefore the concentration that will be subject to absorption:
So, in this case pH = pKa. Hence, when pH is equal to pKa, the drug is ionized halfly. Ionization of drug effects not only the rate at which
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