Pharmacokinetics and Drug Action Overview

Drug Transport Mechanisms

• Lipid solubility, molecular size, and ionization influence the ability of drugs to cross biologic membranes.
• Passive diffusion allows drugs to move from areas of high concentration to low concentration without energy.
• Active transport involves energy expenditure to move drugs against the concentration gradient, often utilizing carrier proteins.
• Facilitated diffusion utilizes specific transport proteins to aid drug movement across membranes but does not require energy.

Pharmacokinetics Processes

• Absorption: The process by which drugs enter the bloodstream; influenced by route of administration, dosage form, and solubility.
• Distribution: Refers to the dispersion of drugs throughout the body's fluids and tissues; affected by blood flow, protein binding, and tissue permeability.
• Metabolism: The chemical modification of drugs by the body, primarily via the liver; involves enzymatic processes that can convert active drugs into inactive forms.
• Excretion: The elimination of drugs from the body, mainly through urine or feces; kidneys play a critical role in this process.

Genomic Variations and Drug Response

• Genetic differences can affect drug metabolism, efficacy, and risk of adverse effects; variations in enzyme activity can lead to altered drug clearance.
• Pharmacogenomics examines how genes influence individual responses to medications, guiding personalized medicine approaches.

Clinical Usefulness of Serum Drug Levels

• Monitoring serum drug levels helps ensure therapeutic efficacy while minimizing toxicity.
• Target ranges for specific drugs can guide dosing adjustments, especially for medications with narrow therapeutic indices.

Receptor Theory of Drug Action

• Drugs exert their effects by binding to specific receptors, leading to physiological changes.
• Agonists activate receptors to produce a response, while antagonists block receptor activation and prevent responses.

Agonist vs. Antagonist Drugs

• Agonists mimic the action of endogenous substances, leading to a biological response.
• Antagonists inhibit the action of agonists or natural ligands, decreasing or nullifying physiological responses.

Drug–Drug Interactions

• Concomitant use of drugs can alter their effectiveness or lead to adverse effects; interactions may enhance, inhibit, or produce unexpected responses.
• CYP450 enzyme system is a key player in drug metabolism interactions; inducers increase metabolism, while inhibitors decrease it.

Drug-Related and Patient-Related Variables

• Factors such as age, weight, gender, organ function, and existing medical conditions influence drug action and efficacy.
• Drug interactions, compliance, and polypharmacy must be considered in individual treatment plans.

Adverse Drug Effects

• Signs and symptoms of adverse effects may include nausea, dizziness, allergic reactions, and organ-specific toxicity.
• Key body systems affected include gastrointestinal, central nervous system, renal, and hepatic systems.

Management of Drug Overdose and Toxicity

• Initial considerations involve assessing airway, breathing, and circulation; determine the substance and amount ingested.
• Supportive care is essential, along with decontamination procedures such as activated charcoal.

Selected Drug Antidotes

• Naloxone counteracts opioid overdose by reversing respiratory depression.
• Acetylcysteine acts as an antidote for acetaminophen toxicity, preventing liver damage when administered timely.

This quiz covers the essential concepts of pharmacokinetics, including how drugs cross biological membranes and the mechanisms of drug movement throughout the body. It also explores individual variations in drug responses due to genomics, the relevance of serum drug levels, and the theories of receptor action. Furthermore, it distinguishes between agonists and antagonists and discusses drug interactions.