At pKa=pH - Conc. of drug is 50% ionic and 50 % non-ionic

At pKa=pH -
a) Conc. of drug is 50% ionic and 50 % non-ionic
b) Absorption of drug is 50% ionic and 50% ionic
c) Conc of drug is 75% ionic and 25 % non-ionic
d) Conc of drug is 25% ionic and 75 % non-ionic
Correct Answer - A
Answer: A - Concentration of drug is 50% ionic & 50 % Non-
ionic
Numerically equal pKa & pH represents 50% drug ionization
pKa is negative logarithm of acidic dissociation of weak electrolyte.
On equal concentrations of ionized & unionized drugs, log 1 is
zero.
Thus, when pKa is numerically equal to pH
(pKa=pH)→ 50 % drug is ionized.