Pharmacodynamics Lecture Flashcards

Comprehensive vocabulary flashcards covering the core concepts, mechanisms, signaling pathways, quantitative metrics, and safety parameters of pharmacodynamics.

Pharmacodynamics

The study of what a drug does to the body, including how drugs act on targets (receptors, enzymes, ion channels), dose-effect relationships, mechanisms of therapeutic, side, and toxic effects, and drug interactions.

Etiotropic therapy

A type of pharmacotherapy that treats the cause of a disease, such as the use of antibiotics for bacterial infections.

Pathogenetic therapy

A type of pharmacotherapy that treats the underlying mechanism of a disease, such as the use of antihypertensives or anti-inflammatory drugs.

Symptomatic therapy

A type of pharmacotherapy that relieves symptoms without addressing the underlying cause of the disease, such as painkillers or cough syrups.

Replacement therapy

A type of pharmacotherapy that replaces a missing natural substance in the body, such as insulin for diabetes or thyroid hormones.

Therapeutic effect

The intended, beneficial effect produced by a drug at normal therapeutic doses.

Side effect

An unwanted but typically predictable effect of a drug, such as dry mouth caused by antihistamines.

Toxic effect

A harmful drug effect that often results from high doses or prolonged use, such as liver damage resulting from paracetamol overdose.

Physicochemical mechanisms of drug action

Mechanisms where drugs act by altering physical or chemical properties such as pH, osmolarity, surface tension, or solubility (e.g., antacids neutralizing stomach acid).

Chemico-biological mechanisms of drug action

Mechanisms where a drug binds to a biological target (such as a receptor, enzyme, ion channel, transporter, or DNA) via ionic, hydrogen, van der Waals, or covalent bonds to alter cellular function.

Receptor

A macromolecule, usually a protein, that binds a drug or natural ligand and initiates a signal transduction cascade that produces an effect.

Ionotropic signaling

Fast chemical signaling in which ligand binding directly opens an ion channel, exemplified by nicotinic receptors.

Metabotropic GPCR signaling

Chemical signaling mediated by G-protein-coupled receptors that activate G-proteins and second messengers (such as cAMP, IP3, DAG), providing slower, amplified responses (e.g., adrenaline receptors).

Enzyme-linked signaling

Chemical signaling where ligand binding activates phosphorylation cascades, exemplified by the insulin receptor.

Nuclear receptor signaling

Intracellular chemical signaling that alters gene transcription, resulting in slow-onset and long-lasting effects, exemplified by steroid receptors.

Specificity

The pharmacological property whereby a drug binds exclusively to a certain receptor type.

Selectivity

The property whereby a drug, at therapeutic doses, affects mainly one receptor subtype or specific tissue.

Nonspecificity

Drug action that occurs without binding to a specific receptor, exemplified by osmotic diuretics and general anesthetics.

Clark–Ariëns model

A pharmacological model describing drug ($D$) binding to receptor ($R$) to form a complex ($DR$) that produces an effect according to the equation: $\text{Effect} = E_{\max} \times \alpha \times [D] / (K_d + [D])$.

Dissociation constant ($K_d$)

The drug concentration at which half of the receptors are occupied; a lower $K_d$ indicates higher binding affinity.

Intrinsic activity ($\alpha$)

The ability of a drug-receptor complex to produce an effect, defined as $\alpha = 1$ for a full agonist and $\alpha = 0$ for an antagonist.

Affinity

A measure of how strongly or how well a drug binds to its specific receptor.

Efficacy (Efficiency)

The maximum pharmacological effect ($E_{\max}$) that a drug can produce.

Potency (Activity)

The amount or concentration of a drug required to produce a given effect; lower $EC_{50}$ or $ED_{50}$ values indicate higher potency.

Full agonist

An agent that binds to a receptor and produces the maximum possible biological effect ($\alpha = 1$).

Partial agonist

An agent that produces less than the maximum effect even at full receptor occupancy, and can act as an antagonist in the presence of a full agonist (e.g., buprenorphine, aripiprazole).

Summation (Additivity)

A combined drug effect that equals the mathematical sum of the individual effects ($1 + 1 = 2$).

Potentiation

A drug interaction where one drug enhances the effect of another drug, even if the enhancing drug produces no effect on its own.

Synergy

A drug interaction where the combined effect of two drugs is greater than the sum of their individual effects.

Competitive antagonist

An antagonist that binds reversibly to the agonist binding site, shifting the dose-response curve to the right without reducing $E_{\max}$; its blockade can be overcome by increasing agonist concentration (e.g., naloxone).

Non-competitive (Allosteric) antagonist

An antagonist that binds to an allosteric site or binds irreversibly, reducing $E_{\max}$; its blockade cannot be overcome by increasing agonist concentration (e.g., phenoxybenzamine).

Physiological antagonism

An antagonism where two drugs act on distinct receptor types to produce opposing physiological effects (e.g., adrenaline versus histamine).

Chemical antagonism

An antagonism where one substance directly inactivates another via chemical interaction, such as protamine neutralizing heparin or chelators binding metals.

Gradual response

A continuous pharmacological response measured across a range of values (e.g., blood pressure, heart rate), commonly used to construct dose-response curves.

Quantum (Alternative) response

An all-or-none pharmacological response (e.g., death, seizure, yes/no pain relief), utilized to determine quantal parameters such as $ED_{50}$ and $LD_{50}$.

Therapeutic index (TI)

A drug safety parameter calculated as $LD_{50}/ED_{50}$ or $TD_{50}/ED_{50}$; higher values indicate a safer drug.

Therapeutic range (TR)

The concentration range between the minimum effective concentration and the minimum toxic concentration of a drug; wider ranges indicate greater safety.

Standard safety margin (SSM)

The extra safety margin or gap between the effective dose and the toxic dose of a drug; larger values denote greater safety.

$$ED_{50}$$

The median effective dose of a drug that produces a specified therapeutic effect in $50\%$ of subjects.

$$EC_{50}$$

The molar concentration of an agonist that produces $50\%$ of the maximum response.

$$LD_{50}$$

The median lethal dose of a drug that causes death in $50\%$ of tested subjects.

Minimal toxic dose

The lowest administered dose of a drug that produces detectable toxicity.

Loading (Initial) dose

A larger initial dose of a drug administered to rapidly achieve therapeutic plasma concentrations.

Course dose

The total cumulative dose of a drug administered over the entire duration of a treatment regimen.

Physical cumulation

Accumulation of the drug molecule itself within the body due to slow clearance, elimination, or metabolism (e.g., digoxin).

Functional cumulation

Accumulation of pharmacological effects over repeated administration even when the drug substance itself does not persist or accumulate (e.g., effects of alcohol).

Tolerance

A decreased pharmacological response following repeated administration of a drug, requiring higher doses to achieve the initial effect.

Tachyphylaxis

Rapidly developing tolerance occurring after only a few doses of a drug.

Sensitization

An increased pharmacological response resulting from repeated drug exposure.

Desensitization

A loss of receptor responsiveness following prolonged or repeated drug exposure.

Idiosyncrasy

An abnormal, unusual individual reaction to a drug that is not mediated by the immune system and is frequently rooted in genetic differences.

Drug allergy

An immune-mediated hypersensitivity reaction to a drug that is not dose-dependent.

Physical dependence

A state of physiological adaptation to a drug characterized by the appearance of withdrawal symptoms when administration is discontinued.

Mental (Psychological) dependence

A psychological state characterized by intense drug craving and compulsive use.

Embryotoxicity

Toxic effects exerted on the developing embryo, capable of causing embryonic death or malformations.

Fetotoxicity

Toxic effects exerted on the developing fetus, which may result in intrauterine growth retardation or functional/organ damage.

Teratogenicity

The capacity of a drug to induce structural or functional birth defects, with the most critical susceptibility window occurring during the first trimester.

Mutagenic effect

The ability of a drug or chemical agent to damage DNA and cause genetic mutations.

Carcinogenic effect

The capacity of a drug or substance to initiate or promote the development of cancer.