Pharmacology Fundamentals

• Pharmacology is the study of medications or drugs and their actions on living organisms.
• Medical pharmacology focuses on the use of chemicals in the prevention, diagnosis, and treatment of disease, especially in humans.
• Toxicology is the study of harmful chemicals/poisons, their effects, detection, and treatment.
• Therapeutics deals with the treatment of diseases.
• Pharmacotherapy is the treatment of disease with medication, involving proper drug selection and use.
• Pharmacognosy involves drug recognition and identification of pharmacologically active chemical agents.
• Pharmacy is the practice of preparing, compounding, and dispensing drugs.
• Pharmacokinetics is the study of what the body does to a drug, including absorption, distribution, metabolism, and excretion.
• Pharmacodynamics is the study of how drugs act on target sites in the body and the effects of the drug on a living system.
• A drug is any substance, other than a nutrient or essential dietary ingredient, that alters the function of living organisms and produces biological effects.
• Medicines are chemical preparations or dosage forms in which drugs are administered.
• The therapeutic effect is the intended primary effect of a drug.
• Side effects are unintended secondary effects of a drug, usually predictable.
• Drug toxicity refers to the toxic effect of the drug on an organism or tissue resulting from overdose.
• A drug allergy is an immunological reaction to a drug.
• A receptor is a biological molecule that interacts with a drug to initiate a process that leads to a pharmacological effect.
• An agonist stimulates a specific receptor to bring about a certain pharmacological effect, possessing both affinity and intrinsic activity.
• An antagonist has an affinity for, but no intrinsic activity on, specific receptors, competing with the agonist for receptor occupation.
• Affinity is a selective power of attraction between the drug molecule and the receptor, measuring how tightly a drug binds.
• Potency is a measure of the amount of drug required to produce a response.
• Efficacy is the maximal response a drug can produce.
• Intrinsic activity is the ability of a drug to stimulate a specific receptor, generating an effect activating stimulus and producing a change in cellular activity.
• Tachyphylaxis is rapid desensitization to a drug's effects following continued stimulation.
• Tolerance occurs when larger doses of a drug are required over time to produce the same pharmacological effect.
• Desensitization is a state where continued stimulation of cells with agonists results in a diminished effect with subsequent exposure to the same drug concentration.
• Drug administration refers to the different ways that drugs can be administered to patients.
• A dosage form constitutes the different forms in which drugs can be administered, such as ointments, tablets, and injections.
• Bioavailability is the fraction of an administered dose that reaches the systemic circulation as intact drug.
• The apparent volume of distribution (Vd) is a mathematical parameter estimating the extent and intensity of the body's exposure to a given drug dose.
• Half-life (t ½) is the time required for the plasma concentration of a drug to decrease by 50%.
• Clearance (CL) signifies the rate at which a drug is removed from the body.
• Steady-state concentration (Css) is the state where the drug in the body is stable, with enough drug given to replace what is eliminated.
• First-pass metabolism is metabolism of a drug during its passage from the gut to the liver, reducing the amount reaching systemic circulation.
• Enterohepatic circulation is a cycle where a drug is absorbed, excreted into the bile, and then reabsorbed from the intestine.

Dose and Response

• The magnitude of the biological response is proportional to the number of drug-receptor complexes.
• A concentration/dose-response curve illustrates this relationship.

Affinity, Potency, and Efficacy

• Affinity measures how tightly a drug binds to a receptor and is a prerequisite for drug-receptor interaction.
• Potency denotes the amount of drug needed to produce a specified effect, often referring to the amount needed to achieve 50% of the maximal effect (EC50).
• Efficacy is the maximal response a drug can produce, determined by the drug's nature, the receptor, and its associated effector system.

Types of Antagonism

• Competitive antagonism occurs when both drugs compete for the same site on the receptor.
• Non-competitive antagonism involves the antagonist binding to a different site, altering the response to the agonist.
• Functional antagonism involves an agonist eliciting an effect at a particular receptor that is opposite to the effect caused by the first agonist at another receptor.
• Chemical antagonism occurs when the antagonist directly interacts with the agonist, reducing its effect.

Two Drugs at the Receptor

• Synergism results in an effect that is the sum of the effects of the two agonists.
• Potentiation results in an effect that is greater than the sum of the effects of the two agonists.
• Antagonism occurs when the effect of an agonist is reduced by the presence of an antagonist.

Drug Targets

• Drug targets include enzyme receptors, transport (carrier) receptors, storage receptors, ion channel receptors, and specific receptors like cholinergic and adrenergic receptors.

Tachyphylaxis, Tolerance, Desensitization

• Tachyphylaxis is a rapid desensitization to a drug's effects with repeated administration.
• Tolerance requires larger doses of a drug over time to achieve the same effect.
• Desensitization is a state of reduced responsiveness to a drug following continued exposure.
• Hypersensitization Note: The provided text does not explicitly define "hypersensitization".

Dose-Response Curve

• A dose-response curve illustrates the relationship between drug concentration and biological response, showing a drug’s affinity, potency, efficacy, and intrinsic activity.

Basic Principles

• Drugs influence existing biologic functions by binding to receptors that influence biochemical and physiological processes in the body.
• Drugs have generic names and trade names.
• The generic name is assigned when the drug is registered for official use
• The trade name is how a manufacturer markets the medicine.
• Sources of drugs include chemical compounds produced in the laboratory, synthetic versions of natural drugs, and molecular bioengineering.
• Essential medicines satisfy the priority healthcare needs of the population.
• Sources of medications include plants, animals, micro-organisms/biological sources, and synthetic chemicals.

Dietitians and Pharmacology Knowledge

• Dietitians need pharmacology knowledge to deal with drug therapy, understand drug-food interactions and nutritional therapy.
• Pharmacological knowledge for a dietitian includes knowledge of drug effects, pharmacotherapy of nutrition-related disorders, oral administration of drugs, and drug-food interactions.

Drug Administration

• Drug administration includes enteral (via the gastrointestinal tract) and parenteral (outside the gastrointestinal tract) routes.
• Local effects occur at the site of application, while systemic effects involve absorption into the bloodstream and distribution throughout the body.
• Examples of routes of administration include application to the skin, application to mucous membranes, oral, rectal, percutaneous, and injections.
• Each route of administration has specific advantages and disadvantages related to onset of action, bioavailability, patient convenience, and potential for local or systemic side effects.

Pharmacokinetics Processes

• Drugs move across cell membranes via filtration, passive diffusion, carrier-mediated transport, or pinocytosis.
• Absorption is influenced by factors such as solubility, concentration, absorbing surface, blood supply, and first-pass effect.
• Distribution is influenced by blood flow, tissue binding, plasma protein binding, and barriers such as the blood-brain barrier.
• Metabolism is the chemical alteration of drugs by the body, primarily in the liver, through Phase I and Phase II reactions.
• Excretion involves the elimination of drugs and metabolites via the kidneys, liver (bile), lungs, and other routes.

Drug Absorption

• Drug solubility, absorbing surfaces, blood flow, and first-pass metabolism affect drug absorption, especially oral absorption.

Therapeutic Index and Drug Toxicity

• The therapeutic index indicates drug safety.
• Drug toxicity refers to the harmful effects of a drug, often from overdose.

Factors Affecting Medication Response

• Pharmacokinetic (absorption, distribution, metabolism, excretion) and pharmacodynamic (drug-receptor interaction) factors, as well as patient adherence, affect medication response.

Patient Adherence

• Factors affecting patient adherence include forgetfulness, experience of side effects, not having medication, alcohol abuse, low literacy level, and depression.

Nomenclature and Classification

• Drugs have generic names and trade names, as well as chemical names based on the IUPAC system.
• Classification of drugs can be based on pharmacological or legal classifications.