Pharmacology Study Guide

Vocabulary flashcards covering core pharmacology concepts from the notes.

Drug

Any substance that, when administered, is capable of altering physiological function within a living organism. This alteration can be beneficial (therapeutic) or harmful (toxic), by interacting with biological systems at a molecular level.

Pharmacology

The comprehensive scientific study of drugs, encompassing their origin, chemical properties, composition, mechanisms of action, effects on living systems (both therapeutic and adverse), absorption, distribution, metabolism, excretion, and clinical uses.

Pharmacotherapeutics

The practical application of pharmacological principles to prevent, mitigate, treat, or diagnose disease. It focuses on the use of drugs in a clinical setting to achieve specific therapeutic outcomes for patients.

Pharmacokinetics (PK)

The study of what the body does to a drug. It describes the quantitative processes of drug absorption into the body, distribution to various tissues, metabolism (biotransformation), and excretion (elimination) from the body (often summarized as ADME).

Pharmacodynamics (PD)

The study of what the drug does to the body. It describes the biochemical and physiological effects of drugs and their mechanisms of action, including the interaction with target receptors, enzymes, or ion channels at a cellular level.

Toxicology

The scientific discipline that studies the adverse effects of chemicals and drugs on living organisms. It investigates the mechanisms by which harmful agents exert their effects, dose-response relationships, and methods for prevention and treatment of poisoning.

Kinetics vs Dynamics (retention tip)

Kinetics: refers to the movement of the drug within the body (what the body does to the drug)

Dynamics: refers to the effects the drug produces on the body (what the drug does to the body).

Chemical Name

The precise scientific designation that describes the molecular structure of a drug. It is based on the rules of chemical nomenclature (e.g., IUPAC) and is unique to each substance.

Generic Name

The official, nonproprietary name given to a drug, often representing its active ingredient. It is a unique name assigned by a regulatory body (e.g., USAN Council) and is publicly available and used in all countries (e.g., Acetaminophen).

Trade Name

The proprietary or brand name given to a drug by the manufacturing company. This name is copyrighted, used for marketing, and often easier to remember and pronounce (e.g., Tylenol for Acetaminophen).

Name confusion

A significant factor contributing to medication errors, with approximately 25\% of such errors stemming from confusion between drug names, particularly sound-alike or look-alike names, requiring careful prescribing and dispensing practices.

Bioequivalence

The property where two pharmaceutical products (e.g., generic and brand-name versions) contain the same active ingredient, are identical in strength, dosage form, and route of administration, and exhibit comparable bioavailability (rate and extent of absorption) and, consequently, similar therapeutic effects.

Switching caution (generic vs brand)

Caution is advised when switching between generic and brand-name versions for certain drugs, especially those with a narrow therapeutic index. Even small differences in excipients or manufacturing processes can subtly alter pharmacokinetics, potentially leading to varied therapeutic responses or adverse effects in sensitive patients.

Schedule I

Drugs classified as having no currently accepted medical use in the United States and a high potential for abuse. Examples include heroin, lysergic acid diethylamide (LSD), marijuana (federally), ecstasy, and peyote. Research and use are highly restricted.

Schedule II

Drugs with a high potential for abuse, which may lead to severe psychological or physical dependence, but which also have accepted medical uses. Examples include morphine, opium, fentanyl, oxycodone, and methamphetamine. Prescription requires a written order, and refills are not allowed.

Schedule III

Drugs with a moderate to low potential for physical and psychological dependence compared to Schedule I or II substances. They have accepted medical uses. Examples include combinations of codeine, buprenorphine, and certain anabolic steroids. Prescriptions may be refilled up to 5\% times in 6\% months.

Schedule IV

Drugs with a low potential for abuse and low risk of dependence compared to Schedule III substances. They have accepted medical uses. Examples include benzodiazepines (e.g., alprazolam, diazepam), zolpidem, and tramadol. Prescription regulations are similar to Schedule III.

Schedule V

Drugs with the lowest potential for abuse and dependence among controlled substances, typically containing limited quantities of certain narcotics. They have accepted medical uses. Many are available over-the-counter in some states with specific record-keeping requirements (e.g., cough syrups with low doses of codeine).

OTC (Over-the-Counter)

Medications that can be purchased without a prescription. While generally considered safe for common, minor ailments when used as directed, they still carry risks of adverse effects, drug-drug interactions, and potential for misuse or masking serious underlying conditions if not used appropriately.

Dose

The specific quantity of a drug administered to a patient at a single point in time or per administration event. It is a component of a larger dosage regimen.

Dosage

The overall regimen of drug administration, specifying the total amount of drug, its frequency, and the duration of therapy (e.g., 10 mg orally twice daily for 7 days). It defines how the doses are delivered over time.

Ceiling Effect

The phenomenon where increasing the dose of a drug beyond a certain point does not result in a further increase in the therapeutic effect. This occurs because all available receptors are saturated, or a physiological maximum response has been achieved, preventing any additional beneficial action.

Potency

A measure of the amount of drug needed to produce a given effect. A drug is considered more potent if a smaller dose is required to elicit a specific magnitude of response, often quantified by its EC_{50} (the effective concentration for 50\% of maximum effect) on a dose-response curve.

Dose-Response Curve

A graphical representation illustrating the relationship between the dose of a drug (typically on the x-axis, often logarithmic) and the magnitude of the pharmacological effect (on the y-axis). These curves are crucial for characterizing a drug's potency, efficacy, and therapeutic range.

Enteral route

Drug administration via the gastrointestinal (GI) tract. This broad category includes oral (most common), sublingual, buccal, and rectal routes, each with distinct absorption characteristics and potential for first-pass metabolism.

Oral

The most common and convenient route of drug administration, involving swallowing the medication. Drugs administered orally are subject to absorption through the GI tract and significant first-pass metabolism in the liver before reaching systemic circulation, which can reduce their bioavailability.

Sublingual/Buccal

Routes of administration where the drug is placed under the tongue or between the cheek and gum. These routes facilitate direct absorption into the systemic circulation via the oral mucosa, effectively bypassing first-pass metabolism in the liver and leading to a more rapid onset of action for certain drugs.

Rectal

Drug administration via the rectum, typically as suppositories or enemas. This route can provide local effects (e.g., for constipation) or systemic effects. It partially bypasses first-pass metabolism (approximately 50\%) and is useful for drugs irritating to the stomach or for patients unable to take oral medication.

Inhalation

Administration of drugs in a gaseous or aerosolized form, allowing for rapid absorption through the vast surface area of the respiratory epithelium in the lungs. This route can achieve both localized effects in the airways (e.g., bronchodilators) and rapid systemic exposure, but carries potential risks of airway irritation.

Intravenous (IV)

Direct injection of a drug into a vein, providing immediate entry into the systemic circulation. This route offers 100\% bioavailability, rapid onset of action, precise dose control, and is ideal for drugs that are poorly absorbed orally or require immediate therapeutic levels.

Intra-arterial

Direct injection of a drug into an artery. This specialized route is used to deliver high concentrations of a drug to a specific organ or tissue (e.g., for chemotherapy of an organ-confined tumor) by bypassing systemic distribution, thereby minimizing systemic side effects.

Subcutaneous (SC)

Injection of a drug into the subcutaneous tissue below the dermis. This route allows for relatively slow and sustained drug release due to the rich blood supply. It is suitable for small volumes of non-irritating solutions and suspensions (e.g., insulin).

Intramuscular (IM)

Injection of a drug into a muscle. Absorption is generally faster than subcutaneous administration due to greater blood flow in muscles and can accommodate larger volumes. It is a common route for vaccines and many stable drugs, including some depot formulations for sustained release.

Intrathecal

Direct injection of a drug into the cerebrospinal fluid (CSF) within the subarachnoid space of the spinal cord. This route is specifically used to bypass the blood-brain barrier, allowing drugs to reach the central nervous system for localized effects (e.g., spinal anesthesia, anti-cancer drugs).

Topical

Application of a drug to a localized area of the skin or mucous membranes (e.g., eyes, nose, vagina) primarily for its local therapeutic effect. The goal is to maximize drug concentration at the site of action while minimizing systemic absorption and associated side effects.

Transdermal

Application of a drug to the skin for systemic absorption, typically using patches or creams. This route provides a continuous, controlled release of the drug into the bloodstream, bypassing first-pass metabolism and offering convenience for sustained therapy.

Bioavailability

The fraction (percentage) of the administered dose of an unchanged drug that reaches the systemic circulation following administration by any route. It is primarily influenced by absorption from the site of administration and any first-pass metabolism.

Passive Diffusion

The movement of a drug across biological membranes from an area of higher concentration to an area of lower concentration. This process requires no cellular energy and is highly dependent on the drug's lipid solubility, molecular size, and the concentration gradient.

Active Transport

A carrier-mediated process involving specific membrane proteins that move drugs across cell membranes, often against a concentration gradient. This process requires metabolic energy (ATP) and is characterized by saturation kinetics, specificity for drug structure, and the potential for competitive inhibition.

Facilitated Diffusion

A carrier-mediated transport mechanism that moves drugs across cell membranes down their concentration gradient. Unlike active transport, it does not directly consume ATP, but it relies on specific membrane carrier proteins and exhibits saturation and specificity.

Ionization

The process by which a drug molecule gains or loses a proton, becoming charged or remaining uncharged (lipid-soluble) forms typically cross cell membranes more readily (e.g., for absorption), whereas (water-soluble) forms are generally trapped in body fluids and excreted more efficiently, highly dependent on the drug's pKa and the local pH.

Barriers

Physiological structures that selectively restrict drug distribution to certain tissues. Key examples include the blood-brain barrier (BBB) and tight junctions, which protect the central nervous system by limiting the passage of many substances, including drugs, based on size, lipid solubility, and active transport systems.

Distribution

The reversible transfer of a drug from the systemic circulation into the various tissues and organs of the body. Factors influencing distribution include tissue permeability (e.g., lipid solubility), regional blood flow (e.g., highly perfused organs), and binding to plasma proteins (e.g., albumin) or tissue components.

Storage

The accumulation of drugs in certain tissues, acting as reservoirs. Adipose tissue is a primary reservoir for lipid-soluble drugs due to its large volume; other storage sites include bone, muscle, and specific organs. Drug storage can prolong drug action or, upon release, potentially lead to delayed toxicity.

Excretion

The irreversible removal of the parent drug and its metabolites from the body. The kidneys are the primary route for most drugs via glomerular filtration, tubular secretion, and partial reabsorption. Other routes include hepatic elimination into bile, lungs (for volatile anesthetics), sweat, saliva, and breast milk.

Biotransformation (Metabolism)

The chemical modification of drugs within the body, primarily by enzymes, into more polar (water-soluble) compounds. The main purpose is to facilitate excretion, but it can also activate prodrugs or produce active/toxic metabolites. It occurs predominantly in the liver (Phase I: oxidation, reduction, hydrolysis; Phase II: conjugation).

Cytochrome P450 (CYP450)

A superfamily of heme-containing enzymes primarily located in the liver (and other tissues) that are responsible for the oxidative metabolism of a vast number of endogenous and exogenous substances, including most drugs (Phase I reactions). Genetic polymorphisms, induction, and inhibition of these enzymes are major sources of drug interactions and variability in drug response.

Half-Life (t_{1/2})

The time required for the concentration of a drug in the plasma to decrease by 50\% (one-half). It is a key pharmacokinetic parameter that determines the frequency of dosing needed to maintain therapeutic drug levels, the time to reach steady-state concentrations (typically 4-5 half-lives), and the time for complete drug elimination.

Tolerance

A phenomenon where repeated drug administration leads to a decreased pharmacological response, requiring higher doses to achieve the same effect. Mechanisms include pharmacokinetic tolerance (e.g., enzyme induction leading to faster metabolism), pharmacodynamic tolerance (e.g., receptor downregulation or desensitization), or behavioral factors.

Genetics

Individual genetic variations (polymorphisms) significantly influence drug metabolism (e.g., variant CYP450 enzymes), drug targets (e.g., altered receptor sensitivity), and transporters. This pharmacogenomic variability explains why patients respond differently to the same drug, impacting efficacy and the risk of adverse drug reactions.

Disease

Various disease states significantly alter drug pharmacokinetics and pharmacodynamics. Hepatic dysfunction (e.g., cirrhosis) impairs metabolism, renal dysfunction (e.g., kidney failure) reduces excretion, and GI disorders can affect absorption. These changes necessitate dose adjustments to prevent toxicity or ensure efficacy.

Age

Physiological changes associated with age impact drug response. Older individuals, for example, often exhibit reduced renal and hepatic function, decreased lean body mass, increased body fat, and altered receptor sensitivity, leading to increased drug half-lives, higher plasma concentrations, and greater sensitivity to drug effects.

Diet

Dietary factors can significantly influence drug pharmacokinetics. For instance, grapefruit juice can inhibit the intestinal CYP3A4 enzyme, leading to increased oral bioavailability and potentially toxic plasma concentrations of some drugs (e.g., statins). Food can also alter drug absorption rates or amounts.

Sex

Biological sex differences exist in drug pharmacokinetics and pharmacodynamics. These can include variations in gastric emptying time, body composition (fat-to-water ratio), enzyme activity (e.g., alcohol dehydrogenase, some CYP450s), and hormonal influences, which may necessitate different dosing strategies or explain variable side effect profiles between men and women.

Other factors

Numerous other patient characteristics and lifestyle choices influence drug response. These include smoking (induces certain metabolic enzymes), alcohol consumption (affects liver function and enzyme activity), obesity (alters volume of distribution for lipid-soluble drugs), and exercise (impacts blood flow and organ perfusion), all contributing to inter-individual variability.

Over-Prescribing in the US (2012)

In 2012, the US faced a significant crisis due to over-prescribing, resulting in approximately 2.1 million individuals addicted to prescription pain medications, 1.4 million emergency department visits related to drug misuse, and over 22,000 deaths attributed to prescription drug overdose, highlighting a critical public health issue.

Direct-to-Consumer Ads (DTCA) impact

The introduction of Direct-to-Consumer Advertising (DTCA) in the US during the 1990s significantly altered pharmaceutical marketing. By directly promoting prescription drugs to the public, DTCA has contributed to increased patient requests for advertised medications, potentially influencing prescribing patterns and driving up prescription rates.

ADRs increase (1995–2005)

Between 1995 and 2005, there was a dramatic increase (approximately 600\%) in reported adverse drug reactions (ADRs), with the overall number of ADRs concurrently tripling. This rise underscored growing concerns about drug safety, polypharmacy, and the impact of widespread drug use on patient health.

Pharma influence on thresholds

The pharmaceutical industry's influence can contribute to the lowering of diagnostic thresholds for certain conditions, potentially leading to 'disease mongering.' This phenomenon can broaden the definition of illnesses or medicalize normal human experiences, resulting in an increased number of diagnosed patients and, consequently, greater prescription of medications.

Black box warnings

The strongest safety warning that the FDA requires on prescription drug labeling. It alerts healthcare providers and patients to serious or life-threatening risks associated with the drug's use. Notably, approximately 90\% of the most heavily advertised medications in the past carried such warnings, indicating significant safety concerns for widely promoted drugs.