Pharmacology Drug Administration Quiz

Pharmacology - Pharmacokinetics and Pharmacodynamics

• Pharmacology is the study of how drugs affect the body
• Neuropharmacology focuses on the effects of drugs on the brain and subsequent actions on behavior
• Drug actions refer to specific molecular changes resulting from drug binding to a receptor
• Drug effects involve widespread alterations in physiology or psychology arising from drug actions
• Pharmacokinetics examines the factors influencing drug bioavailability and efficacy within the human body—everything besides the actions of the drug

Learning Objectives

• Understanding and applying pharmacokinetic principles, focusing on drugs impacting the brain.
• Examining drug administration and absorption mechanisms, distribution, metabolism, and excretion pathways
• Reviewing receptor-ligand interactions and distinguishing among ligand-receptor, drug-receptor, and enzyme-substrate interactions.
• Differentiating between drug-receptor interactions, resulting effects, agonists versus antagonists, competitive and non-competitive binding, allosteric effects, and partial/inverse agonists.
• Describing long-term drug use effects such as drug tolerance, sensitization, and dependence.

Neuro-Psychopharmacology

• Neuro-psychopharmacology studies drug effects on the central nervous system and the resultant impact on human behavior.

Principal Components (ADME)

• Absorption: Drug administration and absorption into body fluids (e.g., bloodstream)
• Distribution: Drug dispersal throughout body fluids to target tissues
• Metabolism: Biotransformation or inactivation of drugs into metabolites.
• Excretion: Removal of substances or metabolites from the body

Routes of Administration

• Oral (PO): Preferred for clinical use; drugs are absorbed through the gastrointestinal tract.
• Intravenous (IV): Most rapid; drugs are directly injected into the bloodstream.
• Intramuscular (IM): Used for slow, even distribution; drugs are injected into muscle tissue.
• Subcutaneous (SC): Drugs are injected into the fatty tissue beneath the skin.
• Inhalation: Drugs are inhaled and absorbed by the lungs; this method is frequently used for rapid effects
• Intranasal: Drugs are administered through the nasal passages/membranes.
• Sublingual: Drugs are placed under the tongue for rapid absorption.
• Transdermal: Drugs are absorbed through the skin..
• Intraperitoneal: Used in animals for direct access to the abdominal cavity
• Intracranial: Used to deliver drugs directly into the cerebrospinal fluid (CSF), but mostly for experiments due to difficulty in humans
• Intracerebroventricular, intracisternal, intrathecal: Used for delivery to CSF, but mostly for experiments on animals.

Pharmacokinetic Factors

• First-pass metabolism: Drug breaks down in the liver prior to reaching the systemic circulation, decreasing its bioavailability.
• Blood-brain barrier (BBB): Limits passage of many drugs to the brain; only lipophilic substances cross easily.
• Depot binding: Drugs bind to inactive sites; this reduces the amount of free drug and can impact the efficacy and duration of action
• Competition among drugs: Different drugs compete for binding to the same receptor or metabolizing enzymes, affecting efficacy.
• Drug polarity: Nonpolar, lipid-soluble drugs readily diffuse across cell membranes; polar, charged drugs face greater barriers.
• Factors affecting absorption: Drug concentration, physiological factors (e.g., body size, age, pH), metabolic or digestive breakdown, and drug solubility. -Factors affecting absorption:** Intrinsic drug properties (especially polarity and solubility), pH of body compartments, and surface area of absorption sites (e.g., stomach versus intestines).
• Other Factors that Influence Metabolism:
• Enzyme induction: Repeated use of a drug can lead to increased levels of liver enzymes, which may lead to increased metabolism of other drugs.
• Enzyme inhibition: Certain drugs can inhibit enzymes involved in metabolism, which can lead to increased levels of other drugs in the blood.
• Drug Competition: Competition for enzymes may prevent some drugs from being metabolized efficiently.
• Individual differences: Different individuals have different rates of metabolism due to factors like age, sex, and genetics.

Drug Metabolism

• Biotransformation and elimination affect bioavailability
• Primarily occurs in the liver under control of microsomal enzymes (e.g., cytochrome P450 (CYP) system).
• Metabolism often involves two phases; Phase I often involves altering the drug structure while Phase II often involves conjugation of the altered drug with other substances.
• Factors influencing metabolism: enzyme induction/inhibition, drug competition, individual variability.

Drug Excretion

• Primary means of drug excretion is through urine after filtration by the kidneys.
• Drugs are typically eliminated via first-order kinetics (exponential elimination).
• Important physiological factors: rates, and potential for individual variation

Key Points of Pharmacokinetics

• Administration and absorption are critical
• Distribution affects drug actions, depot binding is a factor
• Drug metabolism changes drug structure and efficacy
• Excretion removes drugs through various pathways.