Drug-Receptor Concepts in Pharmacology Lecture Quiz

Pharmacology is the study of drug-body interaction, including the action of drugs on the body and the body's response to drugs.

Pharmacology has three main branches: Pharmacodynamics (study of drug effects), Pharmacokinetics (study of how the body deals with drugs), and Pharmacotherapeutics (study of drug use in disease treatment).

Drugs interact with biological systems in two ways: non-specific and specific.

Non-specific drugs act in a simple physical or chemical manner, such as antacids, and lack any specific structure-activity relationship.

Specific drugs interact with specific macromolecular or cellular targets in the body called receptors, showing clear-cut structure-activity relationship and producing biological effects at very low doses.

Drug receptors are protein or glycoprotein molecules, located on the cell membrane or inside the cell.

There are different types of drug targets or receptors, including classical receptors, ion channels, enzymes, and carrier or transport proteins.

Drug-receptor interactions occur when the drug's molecular structure and shape are similar to those of natural chemical messengers, leading to a complementary fit between the drug molecule and the receptor binding site.

The drug-receptor interaction forms a reversible drug-receptor complex through a "lock and key" relationship, with selectivity determined by both chemical and biological or tissue selectivity.

The fraction of receptors occupied by the drug depends on the drug concentration and the equilibrium dissociation constant (KD) for the drug-receptor complex.

The drug effect is proportional to the fraction of receptors occupied, with maximum drug effect occurring when all receptors are occupied.

The drug concentration-effect relationship follows a sigmoidal curve, with drug concentration on the log scale plotted against effect.

Drug-Drug Interactions is a topic covered in MPharm PHA112 Drug Receptor Concepts during Week 12.

Drug antagonism is a type of Drug-Drug Interaction where the effect of one drug is diminished or abolished in the presence of another.

There are different types of drug antagonism: competitive, non-competitive, chemical, pharmacokinetic, and physiological or functional.

In competitive antagonism, both the agonist and antagonist drugs compete for the same receptor binding site.

Reversible competitive antagonism occurs when both drugs bind reversibly to the receptor, and the fraction of receptors occupied depends on their relative receptor affinities and concentrations.

Irreversible competitive antagonism occurs when the antagonist drug binds irreversibly to the receptor, rendering a fraction of receptors permanently unavailable for agonist drug binding.

Non-competitive antagonism occurs when the antagonist drug does not compete with the agonist drug for the same receptor binding site but may bind to a different site on the receptor or interfere with response coupling.

Chemical antagonism results from a direct interaction between the antagonist and agonist drugs, rendering the agonist drug inactive or unavailable to interact with its target receptors.

Pharmacokinetic antagonism occurs when the antagonist drug reduces the effective concentration of the active drug at its site of action, possible mechanisms include reduced absorption, increased metabolic degradation, or increased renal excretion.

Physiological or functional antagonism occurs when two drugs elicit opposing responses, cancelling out each other's effects, and acting on different receptors.

Summation or additivity refers to the combined effect of two drugs being equal to the algebraic sum of their individual effects when they elicit the same overt response, regardless of their mechanism of action.

Synergism or potentiation refers to the conjoint effect of two drugs being greater than the algebraic sum of their individual effects, the synergist may act to increase the concentration of the other drug at its receptor sites.