Pharmacology: Basic Principles and Pharmacokinetics

• Pharmacology is the study of drugs and their effects on living organisms
• It encompasses how drugs are absorbed, distributed, metabolized, and excreted (ADME), as well as their mechanisms of action and therapeutic and toxic effects

Basic Principles

• Pharmacokinetics describes what the body does to the drug (ADME)
• Pharmacodynamics describes what the drug does to the body

Pharmacokinetics: Absorption

• Absorption is the process by which a drug enters the bloodstream from its site of administration
• Factors affecting absorption include route of administration, drug formulation, blood flow, and membrane permeability
• Oral administration involves absorption from the gastrointestinal tract, which can be affected by gastric pH, intestinal motility, and food intake
• Intravenous administration bypasses absorption, providing immediate and complete bioavailability

Pharmacokinetics: Distribution

• Distribution is the process by which a drug reversibly leaves the bloodstream and enters the tissues
• Factors affecting distribution include blood flow, tissue permeability, protein binding, and volume of distribution (Vd)
• Volume of distribution (Vd) relates the amount of drug in the body to the plasma concentration; a high Vd indicates extensive distribution into tissues

Pharmacokinetics: Metabolism

• Metabolism (biotransformation) is the process by which the body chemically modifies drugs
• It often occurs in the liver and involves Phase I (oxidation, reduction, hydrolysis) and Phase II (conjugation) reactions
• Cytochrome P450 (CYP) enzymes are a major group of enzymes involved in drug metabolism
• Prodrugs are inactive compounds that are metabolized into active drugs

Pharmacokinetics: Excretion

• Excretion is the process by which drugs are removed from the body
• The kidneys are the primary organ for excretion, involving glomerular filtration, tubular secretion, and tubular reabsorption
• Other routes of excretion include the bile, feces, sweat, and lungs
• Clearance is the rate at which a drug is removed from the body

Pharmacodynamics: Receptors

• Receptors are proteins that bind to drugs and mediate their effects
• Ligand-gated ion channels, G protein-coupled receptors (GPCRs), enzyme-linked receptors, and intracellular receptors are major receptor types
• Agonists activate receptors, while antagonists block receptors

Pharmacodynamics: Dose-Response Relationship

• The dose-response relationship describes the relationship between the dose of a drug and the magnitude of its effect
• Efficacy is the maximum effect a drug can produce
• Potency is the amount of drug needed to produce a given effect
• The therapeutic index (TI) is a measure of drug safety, comparing the dose required for a therapeutic effect to the dose that causes toxicity

Drug Interactions

• Drug interactions occur when one drug affects the activity of another
• Pharmacokinetic interactions involve alterations in ADME
• Pharmacodynamic interactions involve additive, synergistic, or antagonistic effects

Adverse Drug Reactions

• Adverse Drug Reactions (ADRs) are unintended and undesirable effects of drugs
• These can range from mild to severe, and include side effects, allergic reactions, and idiosyncratic reactions

Key Drug Classes: Analgesics

• Opioids (e.g., morphine, codeine) are used for pain relief and act on opioid receptors in the central nervous system (CNS)
• Nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., ibuprofen, aspirin) inhibit cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis and inflammation

Key Drug Classes: Cardiovascular Drugs

• Antihypertensives (e.g., ACE inhibitors, beta-blockers) are used to lower blood pressure
• Statins (e.g., atorvastatin, simvastatin) lower cholesterol by inhibiting HMG-CoA reductase

Key Drug Classes: Central Nervous System (CNS) Drugs

• Antidepressants (e.g., SSRIs, tricyclic antidepressants) are used to treat depression
• Anxiolytics (e.g., benzodiazepines) are used to reduce anxiety

Key Drug Classes: Antimicrobial Drugs

• Antibiotics (e.g., penicillin, tetracycline) are used to treat bacterial infections
• Antivirals (e.g., acyclovir, oseltamivir) are used to treat viral infections
• Antifungals (e.g., fluconazole, amphotericin B) are used to treat fungal infections

Autonomic Nervous System Pharmacology

• The autonomic nervous system (ANS) controls involuntary functions
• The sympathetic nervous system (SNS) mediates the "fight or flight" response, using norepinephrine as its primary neurotransmitter
• The parasympathetic nervous system (PNS) mediates the "rest and digest" response, using acetylcholine as its primary neurotransmitter
• Adrenergic drugs affect the SNS, while cholinergic drugs affect the PNS

Endocrine Pharmacology

• Hormones regulate various physiological functions
• Insulin lowers blood glucose levels
• Thyroid hormones regulate metabolism
• Corticosteroids have anti-inflammatory and immunosuppressant effects

Toxicology

• Toxicology is the study of the adverse effects of chemicals on living organisms
• Dose-response relationships are used to assess toxicity
• Antidotes are used to counteract the effects of toxins