Pharmacology Basics: Drug Absorption and Action

Pharmacological Concepts

• Absorption: Movement of drug molecules from administration site into the bloodstream.
• Affinity: Tissues' ability to attract and store drugs in higher concentrations compared to other tissues.
• Blood-Brain Barrier: Selective permeability of capillary blood vessels, allowing only certain substances to enter brain tissue.
• Diffusion: Movement of molecules from areas of higher concentration to lower concentration.
• Distribution: Transport of drugs throughout the body after absorption.

Drug Interaction and Processing

• Drug-Protein Complexes: Occur when drugs bind reversibly to plasma proteins like albumin, rendering them unavailable for action.
• Enterohepatic Recirculation: Recycling process of drugs and substances through bile circulation between intestine and liver.
• Enzyme Induction: Stimulating the activity of liver microsomal enzymes by a drug.
• Excretion: Removal of substances from the body.
• First-Pass Effect: Drugs are metabolized in the liver after absorption, reducing their bioavailability before reaching circulation.

Biological Barriers and Metabolism

• Fetal-Placental Barrier: Anatomical barrier that restricts many chemicals and drugs from entering the fetus.
• Hepatic Microsomal Enzyme System: Liver enzymes, often referred to as P-450 System, involved in drug metabolism and processing.
• Isozymes: Variants of an enzyme that execute slightly different metabolic functions.

Dosing Information

• Loading Dose: Initial large dose for quick therapeutic response.
• Maintenance Doses: Consistent drug amount that keeps plasma concentration within the therapeutic range.
• Metabolism: Process of chemically altering a drug within the body, also called biotransformation.

Drug Concentration and Effects

• Minimum Effective Concentration: The smallest amount of a drug needed to produce a therapeutic effect.
• Pharmacokinetics: Study of how drugs move through the body.
• Plasma Half-Life: Time for the plasma concentration of a drug to reduce by half after administration.
• Prodrugs: Inactive drugs that become active after metabolism.
• Substrate: A drug that is metabolized by a specific CYP enzyme.

Therapeutic Monitoring

• Therapeutic Drug Monitoring: Monitoring plasma levels for drugs with low safety profiles to predict effectiveness or toxicity.
• Therapeutic Range: Dosage range producing the desired effects without toxicity.
• Toxic Concentration: Drug levels that lead to serious adverse effects.

Pharmacodynamics

• Agonist: Drugs that activate receptors, mimicking endogenous substances.
• Antagonist: Agents that block receptor responses to other drugs.
• Dose-Response Relationship: Patient response to different drug doses.
• Efficacy: Maximum response achievable by a specific drug.
• Frequency Distribution Curve: Graphical representation of patient responses at varying doses.

Unique Responses

• Idiosyncratic Response: Unpredictable and unexplained reactions to drugs.
• Intrinsic Activity: Drug's ability to bind to receptors and elicit a strong action.
• Margin of Safety (MOS): Lethal dose for 1% of animals divided by the dose effective for 99%.
• Median Effective Dose (ED50): Dose required for therapeutic response in 50% of patients.

This quiz covers essential pharmacological concepts, including drug absorption, affinity, and the blood-brain barrier. Additionally, it explores drug interactions and processing mechanisms such as enterohepatic recirculation and enzyme induction. Test your knowledge on how drugs are distributed, excreted, and interact within the body.