Which of the following best describes the drug phenomenon at pKa=pH?
pka is numerically equal to the pH at which a drug is 50% ionized. The pKa of a drug is the hydrogen ion concentration (pH) at which 50% of the drug exists in its ionized hydrophilic form (i.e., in equilibrium with its un-ionized lipophilic form) pKa is a different term than pH pH is simply a measure of the concentration in a given solution pKa is defined as the pH were a drug exists as 50% ionized and 50% unionized If pKa-pH = 0, then 50% of drug is ionized and 50% is unionized Ref: KDT 7th edition Pgno: 11,12
Drug exists as 50% ionized and 50% unionized
Drug exists as 25% ionized and 75% unionized
Drug exists as 75% ionized and 25% unionized
Drug is completely (100%) Ionized
General pharmacology