Mechanisms of Drug Action

Question 1

What are the different types of drug receptors?

Answer 1

The different types of drug receptors include ion channel receptors, G protein-coupled receptors, and membrane-bound enzymes.

Question 2

How do bulk forming laxatives and antacids exert their molecular mechanisms of action?

Answer 2

Bulk forming laxatives and antacids exert their molecular mechanisms of action through a direct physiochemical effect.

Question 3

Give an example of a drug that acts on ion channels.

Answer 3

Digoxin is an example of a drug that acts on ion channels, specifically the Na+/K+-ATPase in cardiac tissue.

Question 4

What is the molecular mechanism of action of proton pump inhibitors (e.g., omeprazole)?

Answer 4

Proton pump inhibitors, such as omeprazole, exert their molecular mechanism of action by inhibiting the K+/H+-ATPase in gastric parietal cells.

Question 5

How do thiazide diuretics exert their molecular mechanism of action?

Answer 5

Thiazide diuretics exert their molecular mechanism of action by blocking Na+ / Cl- co-transport in the renal tubule (symport) through transporter proteins.

Question 6

How can a drug inhibit an enzyme?

Answer 6

A drug can inhibit an enzyme by either binding to the active site, preventing the enzyme from binding to the substrate, or by binding to another site in the enzyme, changing its conformation and rendering it unable to bind to the substrate.

Question 7

Besides inhibition, what other effect can a drug have on an enzyme?

Answer 7

A drug can also activate an enzyme or increase its genetic transcription.

Question 8

What is a receptor?

Answer 8

A receptor is a protein molecule located on the surface or inside a cell that serves as a recognition molecule for a chemical mediator.

Question 9

What is the function of a receptor?

Answer 9

The function of a receptor is to receive an external signal and produce a cellular response in response to that signal.

Question 10

How would you describe drug-receptor interaction?

Answer 10

Drug-receptor interaction refers to the process where a drug interacts with a receptor, leading to modulation of intrinsic physiological functions and potentially changing the amplitude and speed of body functions.

Question 11

What are the effects of drug-receptor interactions?

Answer 11

Drug-receptor interactions can modulate intrinsic physiological functions rather than “having” direct effects, potentially altering the amplitude and speed of body functions.

Question 12

What is an agonist?

Answer 12

An agonist is a substance that binds to a receptor and simulates the physiological regulatory effects of endogenous compounds.

Question 13

What is an antagonist?

Answer 13

An antagonist is a substance that binds to a receptor but does not have regulatory effects. It prevents the binding of endogenous compounds.

Question 14

What is competitive reversible antagonism?

Answer 14

Competitive reversible antagonism occurs when an antagonist competes with an agonist for the binding site on the receptor. The antagonist can be displaced by increasing the concentration of the agonist.

Question 15

What is noncompetitive antagonism?

Answer 15

Noncompetitive antagonism occurs when an antagonist binds to a different part of the receptor than the agonist, thereby inhibiting the receptor’s activity. It is not easily reversible.

Question 16

What is allosteric antagonism?

Answer 16

Allosteric antagonism occurs when an antagonist interacts with a different part of the receptor than the agonist, leading to inhibition of the receptor’s activity.

Question 17

What is functional (or physiological) antagonism?

Answer 17

Functional antagonism refers to drugs that have opposing physiological actions at different receptors, resulting in an overall neutral effect.

Question 18

What is chemical antagonism?

Answer 18

Chemical antagonism occurs when a substance binds to and inactivates the agonist directly, rather than affecting the receptor itself.

Question 19

What are constitutively active receptors?

Answer 19

Constitutively active receptors are receptors that exhibit background activity even in the absence of an agonist. They can be found in certain receptors like histamine receptors and some GABA receptors.

Question 20

What is the two-state model of receptors?

Answer 20

The two-state model describes receptors that can exist in an active state (with constitutive activity) or an inactive state, depending on the presence or absence of an agonist.

Question 21

What are inverse agonists?

Answer 21

Inverse agonists are substances that bind to a receptor and stabilize it in its inactive conformation, leading to a decrease in receptor activity. They have negative activity.

Question 22

How do inverse agonists differ from full or partial agonists?

Answer 22

Inverse agonists decrease receptor activity, unlike full or partial agonists that increase receptor activity.

Question 23

Give an example of the use of inverse agonists.

Answer 23

Antihistamines are an example of inverse agonists. They bind to histamine receptors, preventing further stimulation by histamine, and reduce symptoms such as swelling, pain, and itching.

Question 24

What is drug selectivity?

Answer 24

Drug selectivity refers to a drug’s ability to bind to specific types or subtypes of receptors, such as β1 or β2-adrenoceptors.

Question 25

What is desensitization or tachyphylaxis?

Answer 25

Desensitization or tachyphylaxis refers to the gradual diminishing of a drug’s effect when it is given continuously or repeatedly over a short period of time, usually minutes.

Question 26

What is tolerance?

Answer 26

Tolerance is a term used to describe a more gradual decrease in responsiveness to a drug over a longer period of time, ranging from hours to days or weeks. It is often observed with drugs like opiates, benzodiazepines, barbiturates, and stimulants.

Question 27

What are some mechanisms that can lead to desensitization or tolerance?

Answer 27

Various mechanisms can contribute to desensitization or tolerance, including changes in receptors such as conformational changes and phosphorylation, as well as the translocation of receptors (e.g., up and down-regulation of β-adrenoceptors).

Question 28

What is the dose-response relationship?

Answer 28

The dose-response relationship is a measure of drug activity expressed in terms of the amount of a drug required to produce a given intensity of effect.

Question 29

What is potency in the context of the dose-response relationship?

Answer 29

Potency refers to the concentration of a drug, antibody, or toxicant that induces a response halfway between the baseline and maximum after a specified exposure time. It is often quantified as the half maximal effective concentration (EC50) or half maximal effective dose (ED50) in vivo.

Question 30

What is Cmax and tmax?

Answer 30

Cmax refers to the peak plasma concentration of a drug, while tmax refers to the time it takes for the drug to reach its maximum concentration in the plasma.

Question 31

What is the half-life of a drug (t1/2)?

Answer 31

The half-life of a drug is the time it takes for the plasma drug concentration to reduce by half. It is useful for determining the time taken to reach steady-state concentration and the time required for drug elimination.

Question 32

What does the Area Under the Curve (AUC) represent?

Answer 32

The AUC represents the overall drug exposure, taking into account both the concentration and duration of drug exposure.

Question 33

What is the therapeutic index (TI)?

Answer 33

The therapeutic index is a quantification of the range of drug concentrations within which the drug exhibits maximum efficacy (desired effect) and minimum toxicity in the majority of patients. It is calculated as the ratio of the toxic dose (TD50) to the effective dose (ED50).

Question 34

What does a large therapeutic index (TI) indicate?

Answer 34

A large therapeutic index indicates a wide therapeutic window, meaning there is a substantial range of drug concentrations where the desired effect is achieved while minimizing toxicity.

Question 35

What does a small therapeutic index (TI) indicate?

Answer 35

A small therapeutic index indicates a narrow therapeutic window, meaning there is a limited range of drug concentrations where the desired effect is achieved, and the risk of toxicity is relatively higher.