Principles of Pharmacology - Drug Action at Receptors

Flashcards about principles of pharmacology focusing on drug action at receptors.

What are the two main functions of receptors?

Recognition or detection of extracellular molecules and transduction (bringing about changes in cell activity).

What is the relationship between KD and affinity?

Drugs with high affinity have a low KD.

How is the affinity of a drug for its receptor quantified?

The molar concentration of drug required to occupy 50% of the receptors at equilibrium (KD).

Define the term 'efficacy' in pharmacology.

The ability of a drug to activate the receptor after binding.

What is the key difference between agonists and antagonists?

Agonists have both affinity and efficacy, while antagonists have affinity but zero efficacy.

Name two types of agonists.

Full agonists and partial agonists.

How do full agonists differ from partial agonists in terms of efficacy?

Full agonists have high efficacy, while partial agonists have low efficacy.

What effect do reversible competitive antagonists have on the agonist log concentration vs. response curve?

They produce a parallel shift to the right.

What is a competitive antagonist?

A drug that competes with the agonist for the same site on the receptor but does not activate it.

Define KD.

The molar concentration of a drug required to occupy 50% of receptors at equilibrium.

What is the function of receptors in cell signaling?

Receptors detect extracellular molecules and transduce signals to bring about changes in cell activity.

Name three forms of antagonism produced by drugs.

Chemical, pharmacokinetic, and physiological antagonism.

What characterizes irreversible competitive antagonists?

They produce a non-parallel shift in the agonist log concentration-response curve, and their effects cannot be overcome by increasing agonist concentration.

What is the relationship between affinity and the dissociation rate (k-1)?

Drugs with high affinity have a slow dissociation rate (small k-1).

Explain physiological antagonism.

Two drugs produce opposing effects, canceling each other out, by acting on different receptors.

Are all receptors located in the same part of a cell?

No. Receptors are usually inserted across the lipid bilayer of the cell.

How do receptors interact with chemicals?

Receptors bind chemicals, such as hormones or neurotransmitters, with a high degree of specificity.

Why design drugs that bind to only certain subtypes of receptors?

This leads to drugs with fewer side effects, i.e., drugs that are highly selective in their action.

What happens after an agonist binds to a receptor?

Agonists produce a change in the shape of the receptor, leading to a response in a cell or tissue.

What is the difference between the EC50 and KD for an agonist?

EC50 is the concentration that produces 50% of the maximal response, while KD is the concentration required to occupy 50% of the receptors. They are not usually the same.

What is chemical antagonism?

One drug chemically inactivates another drug.

What is pharmacokinetic antagonism?

One drug alters the way the body processes another.

What is the effect of increasing agonist concentration in the presence of a reversible competitive antagonist?

The inhibitory effects of the antagonist can be overcome.

What is meant by 'surmountable' blockade?

The inhibitory effects of the antagonist can be overcome by increasing the concentration of the AGONIST.

What does the constant k+1 represent?

The rate constant of the forward reaction.

What determines the overall response to an agonist?

Both its affinity and its efficacy.

How does adrenaline activate its receptor?

By causing a conformational change.

What needs to be present for a receptor to 'stick?

Affinity.

If drug 'A' has a KD of 100 nM and drug 'B' has a KD of 10 microM, which has higher affinity?

Drug 'A'.

Define specificity in regards to receptors.

The drugs they bind.