411-Section1: Pharmacology FLASHCARDS

Pharmacology section 1 flash cards

Drug

Any substance that biologically alters the normal physiological functioning of cells, tissues, or organs in an organism. These interactions can lead to beneficial therapeutic effects or harmful toxicities.

Pharmacology

The overarching science studying the effects and uses of substances that interact with biological systems. Specifically, pharmacotherapeutics focuses on employing these substances to prevent, treat, or diagnose diseases by modulating intricate bodily processes.

Pharmacokinetics

This field studies how an organism handles an administered substance over time, encompassing: 1. Absorption, 2. Distribution, 3. Metabolism (biotransformation), and 4. Excretion (ADME). These processes determine the substance's concentration at its site of action and its duration of effect.

Absorption

This is the process by which an administered substance enters systemic circulation (bloodstream) from its administration site (e.g., GI tract, skin). It involves crossing anatomical barriers like epithelial layers, with its rate and extent determining how quickly it reaches target tissues.

Distribution

The reversible dispersion of an administered substance from systemic circulation into various body tissues and fluids. Factors like tissue permeability, blood flow, and plasma protein binding influence this, determining its concentration in target organs and potential storage sites.

Elimination

The irreversible removal of a substance from the body, primarily through metabolism (biotransformation, mainly in the liver) and excretion (typically via kidneys into urine, or bile into feces). Efficient processes prevent accumulation and potential toxicity.

Pharmacodynamics

This field studies what a substance does to the body, focusing on its biochemical and physiological effects, and its mechanisms of action. It involves how these substances interact with receptors, enzymes, or cellular components to produce therapeutic or adverse effects, directly influencing cellular functions and organ systems.

Mechanism of Action

The specific molecular and cellular interactions through which a therapeutic agent produces its pharmacological effects (e.g., binding to receptors, inhibiting enzymes, interfering with metabolic pathways). Understanding this helps predict its effects on physiological systems and potential adverse outcomes.

Adverse Reactions

Any undesirable or harmful effect occurring at therapeutic doses of a substance or above. These effects often manifest across various physiological systems (e.g., CNS, GI, cardiovascular) due to interactions with off-target receptors or disruption of normal processes.

Chemical Name

The precise, often complex and lengthy, scientific name reflecting the exact molecular structure of a therapeutic compound. It's determined by chemical nomenclature rules and provides detailed anatomical information about the molecule, but is rarely used clinically.

Generic Name

The official, nonproprietary name given to a therapeutic agent by a regulatory body, simplified from its chemical structure for widespread use. This universally recognized name identifies the active ingredient and is crucial for safe prescribing across different brands.

Trade Name

The proprietary brand name assigned to a therapeutic product by its manufacturing company, unique to that company. It is typically easier to remember for marketing, distinguishing a specific formulation even though the active ingredient remains the same as its generic counterpart.

Bioequivalence

The property where two therapeutic products (e.g., a generic vs. brand-name formulation) demonstrate comparable bioavailability (rate and extent of absorption) when administered at the same molar dose under similar conditions. This ensures generic formulations yield the same therapeutic effects as brand-name ones by having similar physiological profiles.

Bioavailability

The fraction or percentage of an administered therapeutic dose that reaches the systemic circulation in an unchanged, active form, available to produce its pharmacological effects. Physiologically, it is a critical determinant of therapeutic efficacy and dosage, affected by absorption and first-pass metabolism.

First-Pass Effect

The phenomenon where a significant portion of an orally administered therapeutic agent is metabolized, primarily in the liver (or gut wall), before reaching systemic circulation. This effect markedly reduces its bioavailability, often necessitating higher oral doses compared to other routes.

Dose

The specific amount of medication administered to a patient at a single point in time. Physiologically, this amount determines the initial concentration of the active agent available to engage molecular targets and elicit a response.

Dosage

The total amount of an active agent administered over a specified period, including its frequency, duration, and individual doses. The regimen is designed to maintain therapeutic concentrations of the substance, ensuring sustained efficacy while minimizing adverse effects.

Ceiling Effect

The maximum therapeutic response an active agent can produce. Beyond this point, increasing the dose will not enhance the effect, but only increases the risk of adverse reactions. This occurs when all available receptors or enzyme systems for the agent become fully saturated.

Potency

A measure of the amount of an active agent (dose) required to produce a given intensity of effect. A more potent agent achieves a particular effect at a lower dose than a less potent one, determined by its receptor affinity and efficiency, but does not imply clinical superiority.

Dose-Response Curve

A graphical representation illustrating the relationship between a therapeutic agent's dose and the magnitude of its pharmacological effect. This curve reveals the effective dose range, maximal response (ceiling effect), and potential toxicity, providing insights into its physiological action and optimal therapeutic window.

Enteral

Routes of administration for active agents involving the gastrointestinal (GI) tract, including oral, sublingual, buccal, and rectal methods. Substances absorbed via these routes often pass through the hepatic portal system before reaching systemic circulation.

Oral

The most common and convenient enteral administration method, involving swallowing medication. Primarily absorbed in the small intestine, active agents then pass through the liver (subject to first-pass metabolism). Convenience is balanced by susceptibility to GI pH, enzyme degradation, and first-pass effects.

Sublingual

Administration method where medication is placed under the tongue. The rich capillary supply in the oral mucosa allows rapid absorption directly into systemic circulation, largely bypassing first-pass liver metabolism. This results in a quicker onset and higher bioavailability for certain active agents.

Buccal

Administration method where medication is placed between the cheek and gum. Similar to sublingual, absorption through the oral mucosa directly enters systemic circulation, often avoiding first-pass metabolism. This route offers sustained delivery of the therapeutic agent and improved bioavailability for susceptible active agents.

Rectal

Administration of a therapeutic substance via insertion into the rectum. Absorption into the bloodstream can be variable; lower rectal veins drain directly to systemic circulation, while upper veins drain to the liver. This route is useful when oral administration is unfeasible (e.g., vomiting) or for local effects.

Parenteral

Routes of administration that bypass the gastrointestinal tract, involving injection or infusion (e.g., intravenous, intramuscular, subcutaneous). These routes typically offer more predictable absorption, higher bioavailability (for active agents susceptible to GI degradation), and avoid first-pass metabolism, leading to faster and more controlled systemic levels of the substance.

Inhalation

Administration of a therapeutic agent by breathing it into the lungs (as an aerosol or gas). The large surface area of alveolar membranes and rich blood supply allow rapid absorption into systemic circulation. This route is ideal for local action on the respiratory tract or swift systemic effects.

Intravenous

Administration of a therapeutic substance by injecting it directly into a vein. This route delivers the active agent immediately and entirely into systemic circulation, providing the most rapid onset of action (100% bioavailability). It offers precise control over blood concentrations of the substance and is suitable for large volumes or agents requiring immediate effect.

Intra-arterial

Administration of a therapeutic agent by injecting it directly into an artery. This route allows for the delivery of very high concentrations of the substance directly to a specific target organ or localized tissue area, often minimizing systemic exposure. It's primarily used for diagnostic procedures or localized chemotherapy.

Subcutaneous

Administration of a therapeutic agent by injecting it into the subcutaneous tissue, the fatty layer beneath the skin. This region has lower blood flow compared to muscle, resulting in slower, sustained absorption into systemic circulation. It's suitable for agents that require a prolonged effect or are given in small volumes.

Intramuscular

Administration of a therapeutic agent by injecting it deep into a muscle. Muscles are well-vascularized, allowing relatively rapid absorption into systemic circulation. This route can provide either prompt systemic effects, especially for aqueous solutions, or a sustained release (depot effect) for oily preparations or suspensions, balancing speed with duration of action.

Intrathecal

Administration of a therapeutic agent by injecting it directly into the cerebrospinal fluid (CSF) within the spinal canal (subarachnoid space). This route completely bypasses the blood-brain barrier, delivering active agents directly to the central nervous system for localized effects, such as anesthesia or treatment of CNS infections/cancers, where systemic administration would be ineffective.

Topical

Administration of a therapeutic agent by applying it directly to the surface of the skin or mucous membranes (e.g., eyes, nose, throat, vagina). The substance is intended to act primarily at the site of application. Physiologically, this route often produces a localized effect, minimizing systemic absorption and therefore systemic side effects by targeting superficial tissues.

Transdermal

Administration of a therapeutic agent where the medication is delivered through the skin, typically via a patch, to achieve systemic absorption. The active compound must penetrate the stratum corneum and underlying epidermal and dermal layers to reach the capillaries. Physiologically, this route provides a controlled and sustained release of the substance over an extended period, avoiding first-pass metabolism and maintaining relatively constant plasma levels.

Lipids Solubility

The property of a therapeutic agent that quantifies its ability to dissolve in lipids or fats. Physiologically and anatomically important, a higher lipid solubility allows such an agent to more readily cross lipid-rich biological membranes (e.g., cell membranes, blood-brain barrier) via passive diffusion, impacting its absorption, distribution, and ability to reach intracellular targets.

Ionization

The process by which a therapeutic molecule gains a net electrical charge (becomes an ion). Physiologically, ionized forms of these substances are generally less lipid-soluble and thus poorly penetrate lipid-rich biological membranes. Conversely, the non-ionized (uncharged) form is more lipid-soluble and can more readily cross cell membranes, significantly influencing its absorption, distribution, and excretion based on the pH of the surrounding environment.

Blood-Brain Barrier

A highly selective semipermeable barrier of endothelial cells and astrocytes that tightly regulates the passage of substances from the bloodstream into the central nervous system (CNS). Tight junctions between brain capillary endothelial cells restrict entry of many compounds. Physiologically, this barrier protects the brain from toxins and pathogens, but also limits the access of many therapeutic agents to the CNS, with only highly lipid-soluble ones or those with specific transporters able to cross effectively.

Passive Diffusion

The movement of therapeutic molecules across a biological membrane from an area of higher concentration to an area of lower concentration, without the expenditure of cellular energy. Physiologically, this process is favored by a substance's lipid solubility, small molecular size, and the concentration gradient, representing a primary mechanism for its absorption and distribution across cell membranes.

Active Transport

A carrier-mediated transport mechanism that moves therapeutic molecules across a biological membrane, often against their concentration gradient, requiring the direct expenditure of cellular energy (ATP). Physiologically, this process is vital for the absorption of some nutrients and the elimination of wastes, and it can be a pathway for uptake into cells or efflux out of cells for certain substances, exhibiting saturation and competition.

Facilitated Diffusion

A type of carrier-mediated transport that moves therapeutic molecules across a biological membrane down their concentration gradient, without the direct expenditure of metabolic energy. Physiologically, it involves specific membrane proteins that facilitate the passage of certain substances, exhibiting characteristics such as saturation and competition, and is faster than passive diffusion for specific substrates.

Osmosis

The passive movement of water molecules across a selectively permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration). Physiologically and anatomically essential for maintaining fluid balance, cell volume, and nutrient/waste transport, influencing the environment therapeutic agents encounter.

Tonicity

A measure of the effective osmotic pressure gradient between two solutions (e.g., extracellular fluid and intracellular fluid) across a semipermeable membrane, which influences water movement and cell volume. Physiologically, solutions can be hypotonic (cell swells), hypertonic (cell shrinks), or isotonic (equal solute, no net change), critically impacting how intravenous therapeutic agents are formulated and their effects on cell integrity.

Tissue Permeability

The inherent ability of an active agent molecule to traverse various biological tissue barriers (e.g., cell membranes, capillary walls, blood-brain barrier) to reach its site of action. Anatomically and physiologically, this is determined by the molecule's physicochemical properties (like lipid solubility, ionization, molecular size) and the specific characteristics of the barrier, significantly affecting its distribution and efficacy.

Plasma Protein Binding

The reversible association of an active agent with proteins present in the blood plasma, primarily albumin. Physiologically, only the unbound ('free') fraction of the substance is pharmacologically active, able to diffuse across membranes to exert an effect, or be metabolized and excreted. High protein binding can delay its elimination and influence interactions with other therapeutic agents.

Drug Storage Site

Specific tissues (e.g., adipose tissue, bone, muscle, liver) that can accumulate and temporarily store active pharmaceutical agents. These sites can sequester the agents away from their active sites or sites of elimination, impacting an agent's volume of distribution, prolonging its half-life, and potentially leading to slow release back into circulation or local toxicity.

Biotransformation

The metabolic processes, mainly in the liver, that chemically modify active agents into more water-soluble compounds called metabolites. This process is crucial for preparing substances for excretion, often inactivating them, but can also produce active or toxic compounds.

Cytochrome P450

A superfamily of heme-containing enzymes (CYPs), predominantly in the liver, that are vital for the Phase I metabolism of over 75% of all therapeutic agents. These enzymes can be induced (activity increased) or inhibited (activity decreased) by various substances, profoundly impacting the clearance, efficacy, and propensity for interactions between different therapeutic agents.

Enzyme Induction

A process where exposure to certain therapeutic agents or environmental substances increases the synthesis and/or activity of specific metabolizing enzymes (e.g., cytochrome P450 enzymes) in the liver. This accelerates the metabolism of substrate compounds, potentially leading to decreased therapeutic effects and faster clearance of the agent.

Half-Life

The time required for the concentration of an active agent in the systemic plasma to decrease by 50% (t_{1/2}). This critical pharmacokinetic parameter determines the frequency of administration to maintain therapeutic concentrations, the time to reach steady-state, and the time for elimination from the body.

Drug Clearance

The theoretical volume of plasma from which an active agent is completely and irreversibly removed per unit of time (e.g., mL/min or L/hr). This parameter reflects the efficiency of the agent's elimination by all involved organs (primarily liver and kidneys) and is key in achieving steady-state concentrations of the substance.

Pharmacogenetics

The study of how individual genetic variations (e.g., polymorphisms in genes encoding metabolizing enzymes, transporters, or receptors) influence a person's response to therapeutic agents. This field aims to optimize treatment by personalizing dosages, predicting efficacy, and identifying individuals at risk for adverse reactions based on their unique genetic makeup.

Grapefruit Juice Interaction

A significant interaction between dietary intake (specifically grapefruit juice) and therapeutic agents, where grapefruit juice inhibits the activity of cytochrome P450 3A4 (CYP3A4) enzymes in the intestinal wall. This inhibition reduces first-pass metabolism of orally administered substances, leading to increased bioavailability and systemic concentrations of the active ingredient, potentially causing toxicity or exaggerated therapeutic effects.

Age-Related Sensitivity

The phenomenon where individuals' responses to therapeutic agents can vary significantly with age. Older individuals often show increased sensitivity due to age-related changes like decreased liver and kidney function (impacting metabolism/excretion), reduced lean body mass (affecting distribution), and altered receptor sensitivity, necessitating careful dosage adjustments.

Sex Differences in Pharmacology

The variations observed in the pharmacokinetics and pharmacodynamics of therapeutic agents between biological men and women. These differences stem from factors like body composition, hormonal influences, gastric emptying rates (affecting absorption), and differing activity of metabolizing enzymes. Such variations can impact the efficacy and safety of these agents.

Drug Interactions

Situations where the effects of one therapeutic agent are altered by the concomitant presence of another active compound, or by food, supplements, or environmental chemicals. Physiologically, these interactions can lead to increased or decreased efficacy of the substance, enhanced or diminished toxicity, or entirely new effects, by altering either pharmacokinetic processes (ADME) or pharmacodynamic actions.

Direct-to-Consumer Advertising (DTCA)

The marketing and promotion of prescription medications directly to the general public through various media (e.g., TV, print, internet). While aiming to inform patients, physiologically and medically, this advertising has been linked to increased prescription rates and can raise safety concerns if patients request specific therapeutic agents without full understanding of their appropriateness, risks, or alternatives, potentially influencing patient-doctor interactions and prescribing habits.

Black Box Warning

The strongest safety warning that the U.S. Food and Drug Administration (FDA) requires to appear on the labeling of prescription therapeutic agents, indicating serious or even life-threatening adverse effects. Physiologically and medically, this warning highlights situations where the benefits of such an agent must be carefully weighed against significant risks, providing critical information to healthcare providers and patients to ensure informed prescribing and minimize severe adverse outcomes.