Principles of Drug Action Lecture Notes

This set of flashcards covers vocabulary and key concepts from the 'Principles of Drug Action' lecture, including pharmacokinetics, pharmacodynamics, types of receptors, antagonism, and measures of drug safety.

Pharmakon

The root term for a drug or a poison.

Drug

Any molecule used to alter the body's physiology and function, specifically used to diagnose, cure, treat, or prevent disease.

Indications

Conditions that enable the appropriate administration of a drug as approved by the FDA.

Contraindications

Conditions that make it inappropriate to give a drug, meaning a predictable harmful event will occur if the drug is administered in that situation.

Dosage

The specific amount of a drug that should be given.

Mechanism of Action

The way in which a drug causes its effects; also referred to as its pharmacodynamics.

Pharmacokinetics

The study of the processes by which a drug travels from the point of delivery to its site of action and out of the body.

Pharmacodynamics

The study of the processes by which drugs alter body functions.

Toxicology

The pharmacology of poisons and the harmful effects of any drug.

Generic Name

The assigned name of a drug by which it is known throughout the world, usually agreed upon by the World Health Organization.

Official Name

The name by which a drug is listed in official publications such as the U.S. Pharmacopoeia (USP) or the National Formulary (NF).

Trade Name

The name given by a particular manufacturing company that is the legal owner of that name.

Pharmacological Receptors

Target molecules through which soluble physiological mediators such as hormones, neurotransmitters, and cytokines produce their effects.

Agonists

Drugs that are capable of binding to and activating a receptor.

Antagonists

Drugs that combine with a receptor but do not activate them, thereby reducing the probability of an agonist combining with the receptor and blocking its action.

Affinity

The tendency of a drug to bind to its receptors.

Efficacy

The tendency for a drug, once bound, to activate a receptor.

Ion Channels

Gateways in cell membranes that selectively allow the passage of particular ions, which may be ligand-gated or voltage-gated.

Full Agonists

Drugs that produce a maximal response and have an efficacy of $1$.

Partial Agonists

Drugs that can occupy a receptor but do not give a maximal response, with efficacy values between $0$ and $1$.

Inverse Agonist

Drugs that cause intrinsic or constitutively active targets to become inactive, possessing negative efficacy.

Constitutive Receptor Activity (CRA)

The ability of receptor proteins to spontaneously adopt an active conformation and regulate cellular signaling in the absence of an agonist.

Competitive Antagonism

A form of receptor antagonism where the drug competes for the agonist binding site, causing a parallel shift in the dose-response curve with no change in the maximum response.

Noncompetitive Antagonism

A form of receptor antagonism where the drug binds to an allosteric site, resulting in a decreased maximum response.

Functional/Physiological Antagonism

A situation where two drugs produce opposing effects on the same physiological system, such as eta_2-adrenoceptor agonists causing bronchodilation while cholinergic agonists cause bronchoconstriction.

Pharmacokinetic Antagonism

Antagonism occurring when one drug reduces the effect of another by reducing its absorption, altering its distribution, or increasing its metabolic degradation.

Chemical Antagonism

A situation where two substances combine in a solution to cancel an effect, such as chelating agents binding to heavy metals.

Signal transduction

The process by which extracellular inputs or signals lead to intracellular messages that modulate cellular physiology.

Second (2nd) Messengers

Intracellular chemicals (e.g., $cAMP$, $IP_3$, $DG$, and $Ca^{2+}$) whose concentration changes in response to receptor activation to amplify the first message.

ED50

The drug dose that causes a therapeutic response in $50\%$ of the population.

EC50

The drug concentration that causes $50\%$ of the maximal response.

TD50

The drug dose that causes toxicity in half ($50\%$) of the study population.

Therapeutic Window

The range of doses of a drug that elicits a therapeutic response without unacceptable adverse effects or toxicity.

Therapeutic Index/Ratio (TI)

A method of estimating a drug's margin of safety, calculated as $\frac{TD_{50}}{ED_{50}}$.

Tachyphylaxis

A rapid loss of drug effect that occurs within minutes.

Tolerance

A gradual decrease in responsiveness to a drug that takes hours, days, or weeks to develop.

Refractoriness

A term used mainly in relation to the loss of therapeutic efficacy.

Drug resistance

A term used to describe the loss of effectiveness of antimicrobial or antitumor drugs.

Spare receptors

A condition where the maximum response of a tissue is produced by agonists bound to less than $100\%$ of the available receptors.