1. If the pH of either side of the membrane is different, then the compartment whose pH favours greater ionization will have less amount of drug.
a) True
b) False
Explanation: If the pH of either side of the membrane is different, then the compartment whose pH favours greater ionization will have more amount of drug. And only the ionized or the undissociated fraction of drug.
2. Which of the following equations correct for Henderson-Hasselbach equation for weak acids?
a) PH = pKa – log (Unionized drug concentration /Ionized drug concentration)
b) PH = pKa – log (Ionized drug concentration/ Unionized drug concentration)
c) PH = pKa + log (Ionized drug concentration/ Unionized drug concentration)
d) PH = pKa + log (Unionized drug concentration /Ionized drug concentration)
Explanation: For weak acids, the Henderson-Hasselbach equation is pH = pKa + log (Ionized drug concentration/ Unionized drug concentration). And the % of ionized drug = 10pH-pHKa/1+10PH-pKa * 100.
3. Which of the following equations correct for Henderson-Hasselbach equation for weak bases?
a) PH = pKa – log (Unionized drug concentration /Ionized drug concentration)
b) PH = pKa – log (Ionized drug concentration/ Unionized drug concentration)
c) PH = pKa + log (Ionized drug concentration/ Unionized drug concentration)
d) PH = pKa + log (Unionized drug concentration /Ionized drug concentration)
Explanation: For weak bases, the Henderson-Hasselbach equation is pH = pKa + log (Unionized drug concentration /Ionized drug concentration). And the % of ionized drug = 10pKa-pH/1+10 pKa-pH * 100.
4. What is the pH range of the stomach?
a) 1-4
b) 5-8
c) 1-3
d) 1-8
Explanation: PH range of gut is from 1-8. PH range of stomach is from 1-3 making it the most acidic place in human body. PH range of the intestine (duodenum to the colon) is from 5-8 where most of the drugs get absorbed.
5. What is the pH range of the intestine?
a) 4-5
b) 1-3
c) 1-8
d) 5-8
Explanation: The pH range of the intestine (duodenum to the colon) is anywhere between 5-8, this allows the drugs to get easily absorbed and digested. The small intestine specifically has a pH ranging from 6 to 7.5.
6. Acids in the pKa range 2.5-7.5 are greatly affected by changes in pH making their absorption pH dependent.
a) True
b) False
Explanation: Acids in the pKa range 2.5-7.5 are greatly affected by changes in pH making their absorption pH dependent. Example, NSAIDs like aspirin, ibuprofen and some penicillin analogues. Such drugs can be absorbed from acidic conditions of the stomach.
7. Which one of these is an example of a strong acid drug?
a) Diazepam
b) Ibuprofen
c) Cromolyn
d) Aspirin
Explanation: Diazepam is a very weak basic drug. Ibuprofen and aspirin have pH range 2.5-7.5. Cromolyn pKa is less than 2.5. Thus, making Cromolyn one of the most acidic drug.
8. Which one of these is not an example of a basic drug with pKa range 5-11?
a) Cromolyn
b) Imipramine
c) Amitriptyline
d) Chloroquine
Explanation: Cromolyn pKa is 2.5. Rest all the other drugs are bases of Pka range 5-11. These are morphine analogues. Such drugs are better absorbed from relatively alkaline conditions of the intestine where these molecules largely exist in unionized form.
9. Example of a drug which has PKa > 11 is ________
a) Cromolyn
b) Imipramine
c) Amitriptyline
d) Mecamylamine
Explanation: Cromolyn pKa is 2.5. Imipramine and amitriptyline have pKa range from 5 to 11. Mecamylamine has pKa range greater than 11. These drugs are ionized in the entire pH range of GIT and thus they are poorly absorbed
10. What should be the range of oil/water partition coefficient of any drug?
a) 1-2
b) 3-4
c) 2-3
d) 1-3
Explanation: The octanol/pH 7.4 buffer partition coefficient value for a drug should be in the range of 1-2. This is sufficient for passive absorption across lipodial membranes