Drug Biotechnology Questions and Answers – Drugs Absorption – pH Partition Hypothesis

«
»

This set of Drug Biotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Drugs Absorption – pH Partition Hypothesis”.

1. According to the pH-partition hypothesis which one of the given options doesn’t govern the absorption?
a) The molecular size of the drug
b) PH at the absorption site
c) Lipid solubility of unionized drugs
d) Dissociation constant
View Answer

Answer: a
Explanation: The pH-partition hypothesis tells that for drug compounds with molecular weight more than 100, that are transported by passive diffusion across the cell membrane, the process is governed by the capability of lipid solubility of unionized drugs, the dissociation constant of the drug and pH at the absorption site.
advertisement

2. 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
View Answer

Answer: b
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.

3. 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)
View Answer

Answer: c
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.

4. 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)
View Answer

Answer: d
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.

5. What is the pH range of the stomach?
a) 1-4
b) 5-8
c) 1-3
d) 1-8
View Answer

Answer: c
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.
advertisement

6. What is the pH range of the intestine?
a) 4-5
b) 1-3
c) 1-8
d) 5-8
View Answer

Answer: d
Explanation: PH range of gut is from 1-8. PH range of stomach is from 1-3 making the most acidic organ in the human body. PH range of the intestine (duodenum to the colon) is from 5-8 where most of the drugs get absorbed.

7. 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
View Answer

Answer: a
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.

8. Which one of these is an example of a strong acid drug?
a) Diazepam
b) Ibuprofen
c) Cromolyn
d) Aspirin
View Answer

Answer: c
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.

9. 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
View Answer

Answer: a
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.
advertisement

10. Example of a drug which has PKa > 11 is ________
a) Cromolyn
b) Imipramine
c) Amitriptyline
d) Mecamylamine
View Answer

Answer: d
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.

11. 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
View Answer

Answer: a
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.

12. Ibuprofen a weak acid, in the stomach will be present in which of the given form?
a) Ionized form mostly
b) Non-ionized form mostly
c) Half ionized and half no ionized
d) Will form aggregate
View Answer

Answer: b
Explanation: The pH of the stomach is 1.5. Ibuprofen being a weak acid will be in a unionized form in the stomach. At pH 7.4 in plasma, it will be in ionized form and in the same format pH 5 in the intestine.

13. Nitrazepam a weak base, will be in which form in the stomach?
a) Ionized form mostly
b) Non-ionized form mostly
c) Half ionized and half no ionized
d) Will form aggregate
View Answer

Answer: a
Explanation: The pH of the stomach is 1.5. Nitrazepam being a weak base will be in an ionized form in the stomach. In plasma and small intestine with pH 7.4 and 5 respectively, Nitrazepam will be in unionized form.
advertisement

14. All drugs which are weak acids or acidic in nature will be in a unionized form in the plasma.
a) True
b) False
View Answer

Answer: b
Explanation: Acidic or weak acidic drugs are always present in their ionized form in a basic or neutral environment. In plasma and small intestine with pH 7.4 and 5 respectively, rendering all acidic drug be present in their ionized form.

15. Heroin with pKa 7.8 will be in which form in intestinal pH?
a) Ionized form mostly
b) Unionized form mostly
c) Half ionized and half no ionized
d) Will form aggregate
View Answer

Answer: b
Explanation: Drugs that are moderately weak bases with pKa 5-11 will get ionized at gastric pH, stay unionized at intestinal pH and get absorbed through the intestinal wall. Thus, heroin being a weak base will stay at unionized condition in the intestinal pH. It will not form any aggregate.

Sanfoundry Global Education & Learning Series – Drug and Pharmaceutical Biotechnology.

To practice all areas of Drug and Pharmaceutical Biotechnology, here is complete set of 1000+ Multiple Choice Questions and Answers.

Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

advertisement
advertisement
advertisement
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn