Pharmacology Core Concepts and Pharmacotherapy

Comprehensive vocabulary flashcards covering fundamental concepts, mechanisms of action, and adverse reactions in pharmacology.

Pharmacokinetics

The study of what the body does to a drug, defined by the four properties of absorption, distribution, metabolism, and elimination.

Pharmacodynamics

The study of what a drug does to the body, describing the actions of a chemical agent on receptor targets and the relation between drug concentration and response magnitude.

First-Pass Hepatic Metabolism

The rapid biotransformation of an orally administered drug by the liver or intestinal wall during absorption into the portal circulation, reducing the amount of unchanged drug that reaches systemic circulation.

Bioavailability

The rate and extent to which an active drug ingredient reaches the systemic circulation, calculated as the ratio of the area under the curve (AUC) after non-intravenous administration to the AUC after intravenous administration.

Bioequivalence

The property of two drug formulations showing comparable bioavailability and similar times to achieve peak blood concentrations.

Therapeutic Equivalence

The property of two drug formulations that are pharmaceutically equivalent (same active ingredient, dosage form, and route of administration) with similar clinical efficacy and safety profiles.

Apparent Volume of Distribution ($V_d$)

The hypothetical fluid volume required to contain the total amount of drug in the body at the same concentration measured in the plasma, calculated as $\text{Dose} / C_0$.

Clearance (CL)

The volume of plasma from which all drug is cleared per unit of time, calculated using the relationship $\text{CL} = \frac{0.693 \times V_d}{t_{1/2}}$.

First-Order Kinetics

Linear elimination or metabolism kinetics in which the rate of drug elimination is directly proportional to the plasma drug concentration, clearing a constant fraction of drug per unit of time.

Zero-Order Kinetics

Nonlinear elimination kinetics that occur when metabolic enzymes become saturated ($[C] \gg K_m$), clearing a constant amount of drug per unit of time regardless of drug concentration.

P-Glycoprotein

An ATP-dependent transmembrane efflux pump expressed in the liver, kidneys, placenta, intestines, and brain capillaries that actively pumps drugs out of cells.

Steady-State Concentration ($C_{ss}$)

The equilibrium state achieved when the rate of drug elimination equals the rate of drug administration, typically reached after four to five half-lives.

Loading Dose

A large initial dose or series of doses administered to rapidly achieve the desired therapeutic steady-state plasma concentration, calculated as $\frac{V_d \times C_{ss}}{F}$.

Maintenance Dose

A drug regimen given at regular intervals to maintain steady-state plasma concentrations within the therapeutic window, balancing administration rate with clearance.

Potency

A measure of the concentration of drug required to produce an effect of a given magnitude, evaluated by the concentration that produces $50\%$ of the maximum response ($EC_{50}$).

Efficacy ($E_{max}$)

The maximal biological response produced by a drug when all available receptors are occupied, dependent on receptor complex formation and intrinsic activity.

Partial Agonist

A drug that binds to a receptor with an intrinsic activity between zero and one, failing to produce a full maximal effect ($E_{max}$) even at $100\%$ receptor occupancy and potentially acting as an antagonist in the presence of a full agonist.

Inverse Agonist

An agent with negative intrinsic activity that binds and stabilizes the inactive ($R$) receptor state, shifting equilibrium away from the active ($R^*$) conformation and suppressing constitutive activity below baseline.

Competitive Antagonist

An agent that reversibly binds to the same active site as an agonist, maintaining the inactive receptor state and shifting the agonist dose–response curve to the right (increasing $EC_{50}$) without altering $E_{max}$.

Irreversible Antagonist

An agent that binds covalently to the active site of a receptor, permanently reducing the number of functional receptors available and decreasing agonist maximal efficacy ($E_{max}$).

Allosteric Antagonist

An antagonist that binds to an allosteric site separate from the agonist-binding domain, altering receptor conformation and reducing agonist efficacy ($E_{max}$) without shifting $EC_{50}$.

Functional Antagonism

An antagonistic interaction occurring when two drugs bind to completely separate receptor populations to produce opposing physiologic effects (e.g., epinephrine relaxing bronchial muscle contracted by histamine).

Spare Receptors

A receptor system in which maximal biological response can be achieved while only a fraction of total receptors are bound, facilitated by downstream signal amplification.

Tachyphylaxis

The rapid development of decreased responsiveness or desensitization of receptors following repeated or continuous administration of an agonist.

Therapeutic Index (TI)

The ratio of the median toxic dose to the median effective dose ($\text{TI} = \frac{TD_{50}}{ED_{50}}$), serving as a measure of a drug's relative margin of safety.

Ionotropic Receptors

Cell-surface receptors that form an integral ion channel, opening within fractions of a millisecond upon agonist binding to directly alter membrane potential and ion conductance.

Metabotropic Receptors

Membrane receptors that signal recognition of a bound neurotransmitter through G proteins to modulate intracellular second messengers, generating cellular responses over seconds to minutes.

Acetylcholinesterase (AChE)

A membrane-bound enzyme in the synaptic cleft that terminates cholinergic neurotransmission by rapidly hydrolyzing acetylcholine into acetate and choline.

Nondepolarizing Neuromuscular Blockers

Competitive antagonists (e.g., rocuronium, vecuronium) that block acetylcholine at skeletal muscle nicotinic receptors, preventing membrane depolarization and causing flaccid paralysis that can be reversed by cholinesterase inhibitors.

Depolarizing Neuromuscular Blockers

Agents such as succinylcholine that activate nicotinic receptors at the neuromuscular junction, producing sustained membrane depolarization (Phase I fasciculations) followed by repolarization resistance and flaccid paralysis (Phase II).

Catecholamines

Sympathomimetic amines possessing a 3,4-dihydroxybenzene group (such as epinephrine, norepinephrine, isoproterenol, and dopamine) that show high potency at adrenoceptors, rapid inactivation by COMT and MAO, and poor CNS penetration.

Use Dependence

A property of channel-blocking agents (such as Class I antiarrhythmics) characterized by preferential binding to open or inactivated channels, resulting in greater blockade in tissues that are rapidly depolarizing.

Minimum Inhibitory Concentration (MIC)

The lowest concentration of an antimicrobial agent that prevents visible bacterial growth in vitro after 24 hours of incubation.

Minimum Bactericidal Concentration (MBC)

The lowest concentration of an antimicrobial agent that results in a $99.9\%$ reduction in viable bacterial colony count after overnight incubation in broth dilution.

Postantibiotic Effect (PAE)

The persistent suppression of bacterial growth after antibiotic concentrations have fallen below the minimum inhibitory concentration (MIC).

Concentration-Dependent Killing

A property of antimicrobial agents (such as aminoglycosides and daptomycin) where the rate and extent of bacterial killing increase significantly as peak drug concentration rises relative to the MIC.

Time-Dependent Killing

A property of antimicrobial agents (such as $\beta$-lactams and macrolides) where clinical bactericidal efficacy correlates with the percentage of time serum concentrations remain above the MIC.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Antidepressant drugs that selectively block the serotonin transporter with minimal affinity for norepinephrine transporters, muscarinic, $\alpha$-adrenergic, or histaminic receptors.

Extrapyramidal Symptoms (EPS)

Movement disorders, including acute dystonia, akathisia, and pseudoparkinsonism, caused by antipsychotic-induced blockade of dopamine $D_2$ receptors in the nigrostriatal pathway.

Tardive Dyskinesia

A chronic and potentially irreversible motor syndrome characterized by involuntary choreoathetoid movements of the face, tongue, and limbs following long-term antipsychotic exposure.

Heart Failure with Reduced Ejection Fraction (HFrEF)

Systolic heart failure characterized by impaired myocardial contractility, ventricular chamber enlargement, and decreased ejection fraction.

Thrombus

A blood clot adhering to an intact or injured vessel wall, composed of platelets, fibrin, and cellular elements.

Embolus

An intravascular clot or foreign mass that detaches from its site of origin and floats in the bloodstream, capable of obstructing distant vessels.

Heparin-Induced Thrombocytopenia (HIT)

An immune-mediated adverse reaction to heparin characterized by a sharp decline in circulating platelets and an increased risk of life-threatening arterial and venous thrombosis.

Gray Baby Syndrome

A toxic condition in neonates receiving chloramphenicol, caused by deficient UDP-glucuronyltransferase and immature renal excretion that lead to drug accumulation and mitochondrial ribosomal toxicity.

Cinchonism

A toxic syndrome produced by high doses of quinine or quinidine characterized by tinnitus, headache, blurred vision, vertigo, and nausea.

Salicylism

Mild salicylate intoxication resulting from elevated doses of aspirin, characterized by nausea, vomiting, dizziness, headache, mental confusion, and tinnitus.