MCQ Quiz: Drug Transporters

Welcome, PharmD students, to this MCQ quiz focused on Drug Transporters! These specialized proteins play a critical, yet often underappreciated, role in determining how drugs move into, through, and out of the body—a vital aspect of ADME (Absorption, Distribution, Metabolism, and Excretion). Understanding the major families of transporters like ABC and SLC, their tissue locations, their impact on drug efficacy and toxicity, and how genetics and drug interactions can modulate their function is essential for modern pharmacotherapy. This quiz will test your knowledge of these crucial gatekeepers of drug disposition. Let’s begin!

1. Drug transporters are proteins primarily involved in:

• a) The chemical modification of drugs within cells.
• b) Moving drugs across biological membranes.
• c) Binding drugs in the plasma to prevent their action.
• d) Regulating the transcription of genes related to drug action.

Answer: b) Moving drugs across biological membranes.

2. The two major superfamilies of drug transporters are:

• a) Cytochrome P450 (CYP) and UDP-glucuronosyltransferases (UGT).
• b) ATP-Binding Cassette (ABC) and Solute Carrier (SLC).
• c) G-protein coupled receptors (GPCR) and Ligand-gated ion channels.
• d) Kinases and Phosphatases.

Answer: b) ATP-Binding Cassette (ABC) and Solute Carrier (SLC).

3. P-glycoprotein (P-gp, MDR1, ABCB1) is a well-known example of which type of transporter?

• a) An SLC uptake transporter.
• b) An ABC efflux transporter that pumps drugs out of cells.
• c) A passive diffusion channel.
• d) A nuclear receptor.

Answer: b) An ABC efflux transporter that pumps drugs out of cells.

4. Solute Carrier (SLC) transporters generally mediate:

• a) ATP-dependent efflux of drugs from cells.
• b) Facilitated diffusion or secondary active transport of drugs and endogenous compounds into or out of cells (often uptake).
• c) The metabolism of drugs in the liver.
• d) The binding of drugs to plasma proteins.

Answer: b) Facilitated diffusion or secondary active transport of drugs and endogenous compounds into or out of cells (often uptake).

5. The expression of P-glycoprotein in the intestinal epithelium primarily affects a drug’s:

• a) Renal excretion.
• b) Oral absorption and bioavailability (by effluxing drug back into the gut lumen).
• c) Distribution into the CNS only.
• d) Rate of metabolism.

Answer: b) Oral absorption and bioavailability (by effluxing drug back into the gut lumen).

6. Organic Anion Transporters (OATs) and Organic Cation Transporters (OCTs), which belong to the SLC superfamily, are crucial for the renal elimination of many drugs via:

• a) Glomerular filtration only.
• b) Passive tubular reabsorption.
• c) Active tubular secretion into the urine.
• d) Metabolism within the kidney tubules.

Answer: c) Active tubular secretion into the urine.

7. Genetic polymorphisms in the SLCO1B1 gene, which encodes the OATP1B1 uptake transporter in the liver, are associated with increased risk of myopathy with which class of drugs?

• a) Beta-blockers
• b) Statins (e.g., simvastatin)
• c) Proton pump inhibitors
• d) Antihistamines

Answer: b) Statins (e.g., simvastatin)

8. Inhibition of an efflux transporter (like P-gp) by one drug can lead to _______ plasma concentrations and potential toxicity of a co-administered drug that is a substrate for that transporter.

• a) decreased
• b) increased
• c) unchanged
• d) rapidly fluctuating

Answer: b) increased

9. The blood-brain barrier (BBB) utilizes efflux transporters such as P-glycoprotein to:

• a) Enhance the entry of all drugs into the brain.
• b) Limit the penetration of many drugs and toxins into the brain, protecting the CNS.
• c) Facilitate the metabolism of drugs within brain endothelial cells.
• d) Increase the permeability of brain capillaries.

Answer: b) Limit the penetration of many drugs and toxins into the brain, protecting the CNS.

10. Drug transporters play a significant role in which of the following pharmacokinetic processes?

• a) Only Absorption
• b) Only Distribution
• c) Only Excretion
• d) Absorption, Distribution, and Excretion (and can influence Metabolism indirectly)

Answer: d) Absorption, Distribution, and Excretion (and can influence Metabolism indirectly)

11. The Breast Cancer Resistance Protein (BCRP, ABCG2) is an efflux transporter that can affect the disposition of drugs like:

• a) Metformin
• b) Rosuvastatin and some chemotherapy agents
• c) Penicillin
• d) Digoxin (primarily a P-gp substrate)

Answer: b) Rosuvastatin and some chemotherapy agents

12. Which of the following is a characteristic of ABC transporters?

• a) They primarily mediate drug uptake into cells.
• b) They utilize ATP hydrolysis to actively transport substrates against concentration gradients.
• c) They are not subject to genetic polymorphisms.
• d) They are only found in the liver.

Answer: b) They utilize ATP hydrolysis to actively transport substrates against concentration gradients.

13. Induction of an efflux transporter in the gut wall would likely lead to _______ oral bioavailability of its substrate drug.

• a) increased
• b) decreased
• c) no change in
• d) more variable

Answer: b) decreased

14. OATPs (Organic Anion Transporting Polypeptides), such as OATP1B1, are primarily _______ transporters located on the sinusoidal membrane of hepatocytes, facilitating drug uptake from blood into the liver.

• a) efflux; canalicular
• b) uptake; canalicular
• c) uptake; sinusoidal
• d) efflux; sinusoidal

Answer: c) uptake; sinusoidal

15. Grapefruit juice can inhibit intestinal CYP3A4 and also potentially inhibit which transporters, leading to complex drug interactions?

• a) P-glycoprotein and OATPs
• b) OCTs only
• c) Renal OATs only
• d) MRPs only

Answer: a) P-glycoprotein and OATPs

16. Pharmacogenomics of drug transporters studies how genetic variations in transporter genes affect:

• a) Only the drug’s chemical structure.
• b) Transporter expression and/or function, leading to inter-individual differences in drug ADME and response.
• c) The patient’s likelihood of adhering to medication.
• d) The cost of medications.

Answer: b) Transporter expression and/or function, leading to inter-individual differences in drug ADME and response.

17. Multidrug Resistance-Associated Proteins (MRPs/ABCC family) are efflux transporters involved in pumping out drug conjugates (e.g., glucuronides) and other substrates, often contributing to:

• a) Enhanced drug absorption.
• b) Biliary and renal excretion of metabolites.
• c) Increased drug penetration into the brain.
• d) Activation of prodrugs.

Answer: b) Biliary and renal excretion of metabolites.

18. Competition between two drugs for the same active tubular secretion transporter in the kidney can result in:

• a) Increased renal clearance of both drugs.
• b) Decreased renal clearance and prolonged half-life of one or both drugs.
• c) Enhanced glomerular filtration.
• d) No change in renal clearance.

Answer: b) Decreased renal clearance and prolonged half-life of one or both drugs.

19. The expression levels of drug transporters can be altered by:

• a) Only genetic factors.
• b) Genetic factors, disease states, and exposure to inducing or inhibiting drugs/substances.
• c) Only the patient’s age.
• d) Only the route of drug administration.

Answer: b) Genetic factors, disease states, and exposure to inducing or inhibiting drugs/substances.

20. Drug transporters are clinically important because they can influence:

• a) The therapeutic efficacy of a drug.
• b) The risk of adverse drug reactions and toxicity.
• c) The development of drug resistance (e.g., in cancer or infectious diseases).
• d) All of the above.

Answer: d) All of the above.

21. Which statement best describes the general direction of substrate movement by ABC efflux transporters?

• a) From outside the cell to inside the cell.
• b) From inside the cell to outside the cell (or into organelles).
• c) Bidirectionally, depending on the concentration gradient.
• d) Only between intracellular organelles.

Answer: b) From inside thecell to outside the cell (or into organelles).

22. If a drug is a substrate for an uptake transporter in the liver (e.g., OATP1B1) and also for an efflux transporter on the canalicular membrane (e.g., MRP2), these transporters work in concert to facilitate:

• a) Renal excretion.
• b) Hepatic uptake from blood and subsequent biliary excretion.
• c) Distribution into the brain.
• d) Absorption from the intestine.

Answer: b) Hepatic uptake from blood and subsequent biliary excretion.

23. Understanding drug transporter interactions is crucial for predicting and managing:

• a) Only pharmacodynamic drug interactions.
• b) Pharmacokinetic drug-drug and drug-food interactions.
• c) Only the drug’s stability in solution.
• d) The drug’s manufacturing process.

Answer: b) Pharmacokinetic drug-drug and drug-food interactions.

24. A patient with a loss-of-function polymorphism in SLCO1B1 might experience _______ plasma concentrations of statins like simvastatin acid, increasing the risk of myopathy.

• a) lower
• b) higher
• c) unchanged
• d) more rapidly cleared

Answer: b) higher (Due to reduced hepatic uptake)

25. The location of drug transporters (e.g., apical vs. basolateral membrane of polarized cells) is critical for determining their role in:

• a) The drug’s chemical classification.
• b) The vectorial transport of drugs across cellular barriers (e.g., absorption, secretion).
• c) The drug’s half-life only.
• d) The drug’s protein binding.

Answer: b) The vectorial transport of drugs across cellular barriers (e.g., absorption, secretion).

26. Which of the following is an example of an SLC transporter family?

• a) ABCB (e.g., P-glycoprotein)
• b) ABCC (e.g., MRPs)
• c) ABCG (e.g., BCRP)
• d) SLC22A (e.g., OATs, OCTs)

Answer: d) SLC22A (e.g., OATs, OCTs)

27. Inhibition of P-glycoprotein at the blood-brain barrier by a co-administered drug could potentially lead to:

• a) Decreased CNS penetration of P-gp substrate drugs.
• b) Increased CNS penetration and potential CNS side effects of P-gp substrate drugs.
• c) No change in CNS drug levels.
• d) Enhanced P-gp expression.

Answer: b) Increased CNS penetration and potential CNS side effects of P-gp substrate drugs.

28. The clinical significance of pharmacogenetic variability in drug transporters is that it can lead to:

• a) All patients responding identically to drugs.
• b) Predictable drug responses in all individuals.
• c) Inter-individual differences in drug absorption, distribution, and elimination, affecting efficacy and toxicity.
• d) The elimination of all adverse drug reactions.

Answer: c) Inter-individual differences in drug absorption, distribution, and elimination, affecting efficacy and toxicity.

29. Rifampin is a known inducer of P-glycoprotein. Co-administration of rifampin with a P-gp substrate drug taken orally would likely _______ the substrate’s oral bioavailability.

• a) increase
• b) decrease
• c) not affect
• d) make more consistent

Answer: b) decrease

30. Drug transporters located in cancer cells can contribute to multidrug resistance (MDR) by:

• a) Increasing the uptake of chemotherapeutic agents into cancer cells.
• b) Actively pumping chemotherapeutic agents out of cancer cells, reducing intracellular concentrations.
• c) Metabolizing chemotherapeutic agents into inactive forms.
• d) Preventing the binding of chemotherapeutic agents to their targets.

Answer: b) Actively pumping chemotherapeutic agents out of cancer cells, reducing intracellular concentrations.

31. A drug that is a substrate for both CYP3A4 metabolism and P-glycoprotein efflux in the intestine may have its oral bioavailability significantly increased by:

• a) An inducer of both CYP3A4 and P-gp.
• b) An inhibitor of both CYP3A4 and P-gp.
• c) An inhibitor of CYP3A4 but an inducer of P-gp.
• d) An inducer of CYP3A4 but an inhibitor of P-gp.

Answer: b) An inhibitor of both CYP3A4 and P-gp.

32. Transporter-mediated drug interactions are of particular concern for drugs with a:

• a) Wide therapeutic index.
• b) Narrow therapeutic index.
• c) Very short half-life.
• d) High degree of metabolism.

Answer: b) Narrow therapeutic index.

33. Which type of transporter primarily relies on electrochemical gradients (e.g., of ions) for energy, rather than direct ATP hydrolysis?

• a) ABC transporters
• b) SLC transporters (many utilize secondary active transport or facilitated diffusion)
• c) Nuclear receptors
• d) G-protein coupled receptors

Answer: b) SLC transporters (many utilize secondary active transport or facilitated diffusion)

34. The expression of drug transporters can vary significantly based on:

• a) Only the patient’s hair color.
• b) Tissue type, genetic factors, disease states, and drug exposure.
• c) Only the time of day.
• d) Only the drug’s formulation.

Answer: b) Tissue type, genetic factors, disease states, and drug exposure.

35. Intestinal OATPs can be inhibited by certain fruit juices (e.g., grapefruit, orange, apple), potentially _______ the absorption of OATP substrate drugs.

• a) increasing
• b) decreasing
• c) not affecting
• d) accelerating

Answer: b) decreasing

36. The role of drug transporters in biliary excretion involves moving drugs and their metabolites from:

• a) The sinusoidal blood into hepatocytes.
• b) Hepatocytes into the bile canaliculi.
• c) The bile back into the blood.
• d) The kidney tubules into the urine.

Answer: b) Hepatocytes into the bile canaliculi.

37. A drug interaction where Drug A inhibits a renal transporter responsible for the secretion of Drug B would lead to _______ renal clearance of Drug B.

• a) increased
• b) decreased
• c) unchanged
• d) faster

Answer: b) decreased

38. The pharmacogenomics of ABCB1 (P-glycoprotein) has been studied extensively, but its clinical predictability for many drugs is complex due to:

• a) Its lack of substrates.
• b) Its expression only in the liver.
• c) Substrate overlap, numerous SNPs with varying functional effects, and influence of non-genetic factors.
• d) Its consistent expression levels in all individuals.

Answer: c) Substrate overlap, numerous SNPs with varying functional effects, and influence of non-genetic factors.

39. If a drug is primarily taken up into hepatocytes by an OATP transporter and then effluxed into bile by MRP2, a defect in MRP2 function could lead to:

• a) Decreased hepatic uptake of the drug.
• b) Increased intrahepatic accumulation of the drug/metabolites and potentially reduced biliary excretion.
• c) Increased renal excretion of the drug.
• d) Faster overall elimination.

Answer: b) Increased intrahepatic accumulation of the drug/metabolites and potentially reduced biliary excretion.

40. What is a key difference in energy requirement between most ABC and SLC transporters?

• a) SLC transporters are always passive, while ABC transporters require ATP.
• b) ABC transporters directly hydrolyze ATP for energy, while many SLC transporters use ion gradients (secondary active transport) or facilitate diffusion.
• c) Both primarily use facilitated diffusion.
• d) Neither requires energy.

Answer: b) ABC transporters directly hydrolyze ATP for energy, while many SLC transporters use ion gradients (secondary active transport) or facilitate diffusion.

41. Knowledge of drug transporters is important in drug development for:

• a) Only designing the color of the pill.
• b) Predicting potential ADME issues, drug interactions, and identifying strategies to overcome poor permeability or efflux.
• c) Only marketing purposes.
• d) Determining the drug’s taste.

Answer: b) Predicting potential ADME issues, drug interactions, and identifying strategies to overcome poor permeability or efflux.

42. The impact of a genetic polymorphism in a drug transporter on a drug’s pharmacokinetics is most pronounced if:

• a) The transporter plays a minor role in the drug’s disposition.
• b) The transporter is a major pathway for that drug’s absorption, distribution, or elimination, and the drug has a narrow therapeutic index.
• c) The drug is administered intravenously.
• d) The patient is taking multiple other medications that are not substrates.

Answer: b) The transporter is a major pathway for that drug’s absorption, distribution, or elimination, and the drug has a narrow therapeutic index.

43. Which statement regarding drug transporters is FALSE?

• a) They can be targets for drug therapy (e.g., transporter inhibitors).
• b) They exhibit substrate specificity, though some have broad specificity.
• c) Their activity is always constant and not influenced by other drugs or physiological conditions.
• d) They are located in various barrier tissues and organs of elimination/uptake.

Answer: c) Their activity is always constant and not influenced by other drugs or physiological conditions.

44. Biliary excretion, often mediated by transporters like BSEP (ABCB11) and MRP2 (ABCC2) on the canalicular membrane of hepatocytes, is a major elimination pathway for:

• a) Small, volatile compounds.
• b) Some drugs and their metabolites, particularly larger, polar, and conjugated compounds.
• c) Only acidic drugs.
• d) Drugs that are not metabolized.

Answer: b) Some drugs and their metabolites, particularly larger, polar, and conjugated compounds.

45. Drug transporters in the kidney tubules contribute to drug elimination by:

• a) Only filtering drugs at the glomerulus.
• b) Secreting drugs from the blood into the tubular fluid and/or reabsorbing drugs from the tubular fluid back into the blood.
• c) Only metabolizing drugs within the tubular cells.
• d) Only affecting urine pH.

Answer: b) Secreting drugs from the blood into the tubular fluid and/or reabsorbing drugs from the tubular fluid back into the blood.

46. The term “vectorial transport” facilitated by drug transporters refers to:

• a) Random movement of drugs across membranes.
• b) Unidirectional movement of drugs across a polarized cell layer (e.g., from gut lumen to blood, or blood to bile/urine).
• c) Drug movement only within the bloodstream.
• d) Drug binding to plasma proteins.

Answer: b) Unidirectional movement of drugs across a polarized cell layer (e.g., from gut lumen to blood, or blood to bile/urine).

47. Inhibition of renal OATs by one drug could _______ the renal clearance of a co-administered OAT substrate, potentially leading to its accumulation.

• a) increase
• b) decrease
• c) not affect
• d) reverse

Answer: b) decrease

48. The clinical relevance of understanding drug transporters for pharmacists includes:

• a) Identifying patients who will never experience side effects.
• b) Counseling patients on potential drug-drug or drug-food interactions involving transporters and recognizing when genetic variations might impact therapy.
• c) Compounding all medications that involve transporters.
• d) Administering genetic tests in the pharmacy routinely.

Answer: b) Counseling patients on potential drug-drug or drug-food interactions involving transporters and recognizing when genetic variations might impact therapy.

49. Drugs designed to target intracellular sites may have their efficacy affected by efflux transporters if they are:

• a) Not substrates for these transporters.
• b) Actively pumped out of the target cells by these transporters.
• c) Actively pumped into the target cells by these transporters.
• d) Only metabolized extracellularly.

Answer: b) Actively pumped out of the target cells by these transporters.

50. The interplay between drug-metabolizing enzymes and drug transporters at barriers like the intestine and liver is crucial in determining:

• a) Only the drug’s color in solution.
• b) The overall oral bioavailability and systemic exposure of many drugs.
• c) Only the drug’s therapeutic target.
• d) The patient’s preference for a dosage form.

Answer: b) The overall oral bioavailability and systemic exposure of many drugs.