Free NAPLEX QBANK Pharmacology and Drug Mechanisms Questions and Answers 1 — Questions and Answers
Question 1: A patient with heterozygous familial hypercholesterolemia is prescribed alirocumab. What is the primary mechanism of action of this medication?
- It directly inhibits HMG-CoA reductase in the liver, reducing cholesterol synthesis.
- It binds to proprotein convertase subtilisin/kexin type 9 (PCSK9), preventing its interaction with LDL receptors. (Correct answer)
- It blocks the intestinal absorption of cholesterol by inhibiting the Niemann-Pick C1-Like 1 (NPC1L1) protein.
- It activates peroxisome proliferator-activated receptor alpha (PPAR-α), increasing lipoprotein lipase activity.
Correct answer: It binds to proprotein convertase subtilisin/kexin type 9 (PCSK9), preventing its interaction with LDL receptors.
Alirocumab is a monoclonal antibody that targets and inhibits PCSK9. Normally, PCSK9 binds to LDL receptors on hepatocytes, promoting their degradation. By inhibiting PCSK9, alirocumab prevents this degradation, leading to an increased number of LDL receptors on the liver cell surface, which enhances the clearance of LDL cholesterol from the circulation.
Question 2: A 58-year-old male with newly diagnosed type 2 diabetes mellitus is started on metformin. Which of the following best describes the primary mechanism by which metformin exerts its antihyperglycemic effect?
- It acts as a secretagogue, stimulating insulin release from pancreatic beta cells.
- It inhibits the dipeptidyl peptidase-4 (DPP-4) enzyme, increasing incretin levels.
- Activation of AMP-activated protein kinase (AMPK), leading to decreased hepatic gluconeogenesis. (Correct answer)
- It acts as a sodium-glucose cotransporter-2 (SGLT2) inhibitor in the proximal renal tubules.
Correct answer: Activation of AMP-activated protein kinase (AMPK), leading to decreased hepatic gluconeogenesis.
Metformin's principal effect is to decrease hepatic glucose production (gluconeogenesis). It achieves this primarily by activating the enzyme AMP-activated protein kinase (AMPK) in the liver. It also increases insulin sensitivity in peripheral tissues and decreases intestinal glucose absorption, but the reduction of hepatic gluconeogenesis is its main mechanism.
Question 3: A patient who was recently started on lisinopril for hypertension develops a persistent, non-productive cough. This adverse effect is primarily attributed to the accumulation of which substance in the respiratory tract?
- Bradykinin (Correct answer)
- Angiotensin II
- Aldosterone
- Histamine
Correct answer: Bradykinin
Angiotensin-converting enzyme (ACE) is responsible for both converting angiotensin I to angiotensin II and for breaking down bradykinin. By inhibiting ACE, lisinopril causes an accumulation of bradykinin. Elevated levels of bradykinin in the lungs can irritate cough receptors and stimulate the cough reflex, leading to the characteristic dry, non-productive cough associated with this drug class.
Question 4: A patient is brought to the emergency department with respiratory depression and miosis. An opioid overdose is suspected. Administration of naloxone rapidly reverses these symptoms. By what mechanism does naloxone work?
- It acts as a partial agonist at the mu-opioid receptor, displacing the full agonist.
- It increases the metabolic clearance of opioids by inducing hepatic enzymes.
- It acts as a competitive antagonist at mu, kappa, and delta opioid receptors. (Correct answer)
- It stimulates the release of endogenous endorphins to counteract the opioid effect.
Correct answer: It acts as a competitive antagonist at mu, kappa, and delta opioid receptors.
Naloxone is a pure opioid antagonist that has a high affinity for opioid receptors, particularly the mu-receptor. It works by competitively binding to these receptors, thereby displacing the opioid agonist (like heroin or oxycodone) and rapidly reversing its effects, most critically respiratory depression.
Question 5: Which of the following statements most accurately describes the pharmacological mechanism of selective serotonin reuptake inhibitors (SSRIs) like sertraline?
- They inhibit both serotonin and norepinephrine reuptake transporters with high affinity.
- They block postsynaptic serotonin 5-HT2A receptors while also inhibiting serotonin reuptake.
- They selectively block the presynaptic serotonin transporter (SERT), increasing serotonin concentration in the synaptic cleft. (Correct answer)
- They inhibit the enzyme monoamine oxidase, preventing the breakdown of serotonin.
Correct answer: They selectively block the presynaptic serotonin transporter (SERT), increasing serotonin concentration in the synaptic cleft.
SSRIs, as their name implies, work by specifically and selectively inhibiting the serotonin transporter (SERT) on the presynaptic neuron. This action reduces the reuptake of serotonin from the synapse, which leads to an increased concentration and prolonged availability of serotonin to bind with postsynaptic receptors.
Question 6: The anxiolytic and sedative effects of diazepam are produced by which of the following molecular actions on the GABA-A receptor?
- Directly activating the GABA-A receptor in the absence of GABA.
- Increasing the duration of chloride channel opening when GABA is bound.
- Blocking the reuptake of GABA from the synaptic cleft.
- Potentiating the effects of GABA by increasing the frequency of chloride channel opening. (Correct answer)
Correct answer: Potentiating the effects of GABA by increasing the frequency of chloride channel opening.
Benzodiazepines like diazepam are positive allosteric modulators of the GABA-A receptor. They bind to a site distinct from the GABA binding site, which increases the receptor's affinity for GABA. This potentiation results in an increased frequency of chloride ion channel opening when GABA is bound, leading to enhanced neuronal inhibition and producing anxiolytic and sedative effects.
Free NAPLEX QBANK Pharmacology and Drug Mechanisms Questions and Answers 1
A patient with heterozygous familial hypercholesterolemia is prescribed alirocumab.
What is the primary mechanism of action of this medication?