Question

Digoxin is a drug used to increase the ability of the ventricular muscle to contract and thereby generate better cardiac output in a condition known as congestive heart failure. It is also used to control the transmission of electrical signals through the AV node, in conditions in which the ventricle receives excess signals and begins to beat too fast. Researchers at Sandstone University have developed an antibody fragment (Fab), which binds to the digoxin, thereby preventing its actions in the body. This antibody fragment represents what kind of antagonist/antagonism? Select one:

a. pharmacokinetic

b. competitive

c. chemical

d. physiological

e. irreversible

Answer 1

Answer: C. Chemical

A chemical antagonist reduces the action of an agonist by binding to the agonist. Chemical antagonists will form a chelating complex with agonists and thereby reducing the activity of agonists. Here the newly developed antibody fragment binds to digoxin to block its actions in the body. So the Fab can be classified as a chemical antagonist.

Pharmacokinetic antagonists: One drug affects the metabolism of another drug and eventually reducing the effect of the agonist.

Competitive antagonism: Antagonist binding to the receptor of the agonist and blocking its activity

Physiological antagonism: Antagonist binds to a separate receptor and counteracts the effect of agonist

Irreversible antagonism: Antagonist binding permanently to the agonist receptor with a covalent bonding and blocking agonist activity. They cannot be washed out or displace using competing ligands.