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Pharmacology

General Pharmacology

67 topics with concise breakdowns: definitions, key facts, and classroom questions.

The «General Pharmacology» section is the foundation without which it is impossible to understand how any pill works. Here we analyze two main processes: what the body does to the drug (pharmacokinetics) and what the drug does to the body (pharmacodynamics). We will trace in detail the journey of a molecule from routes of administration and passive diffusion across histohematic barriers to biotransformation in the cytochrome P-450 system and excretion.

In classes and exams, professors are guaranteed to ask about receptor mechanisms of action (ionotropic, metabotropic, catalytic, and intracellular), affinity, agonists, and antagonists. Be sure to pay attention to indicators of bioavailability, volume of distribution, as well as enzyme induction and inhibition—these are the basis of pharmacokinetic modeling.

In addition, the section covers crucial clinical aspects: drug incompatibility, dose calculation, chronopharmacology, and classification of adverse drug reactions. This knowledge will help avoid gross errors in combined drug administration and understand the nature of toxic effects, drug allergy, or dependence.

Section Topics

PharmacokineticsPharmacocineticaBiological barriersBiological barriers are specialized cellular and tissue sPassive diffusionDiffusio passivaIonization of drug substancesIonization of a drug substance is a key factor determining Active transportTransportus activusSLC and ABC family transporter proteinsCell membrane transport proteins determine how quickly a druEndocytosis and paracellular transportEndocytosis is the process by which a cell engulfs large extracellular molecules thRoutes of drug administrationThe route of administration of a medicinal product is the method of delivering a pharmacoloEnteral routes of administrationPer os, Sub lingua, Per rectumEffect of food and GI motility on absorptionFood intake, food composition, and changes in gastrointestinal motility Dosage formsThe dosage form determines how quickly and in what volume the active Bioavailability and presystemic eliminationBioavailability reflects the fraction of the administered drug substance that Parenteral routes of administration (intravenous, intra-arterial)Injectio intravenosaIntramuscular and subcutaneous administrationInjectio intramuscularis, Injectio subcutaneaOther parenteral and local routes of administrationParenteral routes of administration include not only familiar injections, butDistribution of drug substancesDistribution of drug substances is a key stage of pharmacokineticsVolume of distributionApparent volume of distribution ($V_d$) is a crucial hypothetical vMetabolism of drug substancesMetabolism of drug substances is a complex of biochemical reactionsCytochrome P-450 systemThe cytochrome P-450 system represents a crucial enzymatic appNon-CYP enzymes and genetic polymorphismGenetic polymorphism of enzymes not belonging to the cytochrome Excretion of drug substancesExcretion is the process of final elimination of medicinal productsDistribution and elimination phasesAfter administration into the body, a drug substance goes through two keyEffect of age on pharmacokineticsThe patient's age critically determines how the body absorbs, distributesHistohematic barriersHistohematic barriers are highly specialized physiologicalBlood-brain barrierThe blood-brain barrier (BBB) is a protective structure between the bloodRole of P-glycoproteinP-glycoprotein is an active transport protein functioning as a cellBlood-placental barrierThe blood-placental barrier is a selective transport system separatingDistribution and deposition of drug substancesDistribution is the process of penetration of a drug substance (DS)Biotransformation of drug substancesBiotransformation (metabolism) is the process of altering the chemical structuProdrugsProdrugs are pharmacologically inactive precursors of drugsFactors affecting drug metabolismThe rate and efficiency of drug biotransformation are influenced by Enzyme induction and inhibitionEnzyme induction and inhibition are processes of altering the activityPharmacokinetic modelingPharmacokinetic modeling is a mathematical representation ofDrug eliminationEliminatioClearanceClearanceDosing of drug substancesDosing of drug substances is the process of selecting the optimal amountBioavailabilityBioavailability (designated as $F$) is a quantitative parameterAnalysis of pharmacokinetic curvesA pharmacokinetic curve is a graph visualizing differences in kiDrug absorptionAbsorptioPharmacodynamicsPharmacodynamics is a fundamental branch of pharmacology responsible for Pharmacodynamics of membrane receptorsPharmacodynamics studies the mechanisms of action of drug substances and their Catalytic receptorsCatalytic receptors (or enzyme-linked receptors) are a group of membraneIonotropic receptorsIonotropic receptors are receptors that are directly coupled to ionMetabotropic receptorsMetabotropic receptors are membrane structures that transmit signals Intracellular receptorsIntracellular receptors are soluble cytosolic and nuclear proteins that reguChemical bonds of drug substances with receptorsFor a medicinal product to produce an effect, it must bind to Affinity and intrinsic activityAffinity is the ability of a pharmacological substance to bind to Receptor agonists and antagonistsAll drug substances interacting with receptors are divided intoDynamic receptor regulationReceptors are not static entities; their density and responsiveTargets of drug actionTargets of drug action are structures or processes in the bodyTypes of drug actionTypes of drug action constitute a basic classification in pharmacSide effects of medicinal productsA side effect is any unintended and undesirable response of the bodyFactors influencing drug actionThe pharmacological effect of a drug depends not only on its dose, but alsoDoses of drug substancesA dose is a strictly defined amount of a drug substance requiredRepeated administration of medicinal productsDuring repeated or prolonged course administration of drugs, their initialDrug dependenceDrug dependence is an overwhelming need for regularCombined drug actionWith the simultaneous prescription of two or more drugs, their effect mayDrug incompatibility and interactionWith the simultaneous prescription of multiple drugs (polypharmacy), their ChronopharmacologyChronopharmacology is the science studying the dependence of pharmacokinetics andTypes of pharmacotherapyPharmacotherapy is comprehensive treatment of already developed diseases usingClassification of adverse drug reactionsIn modern pharmacology, adverse drug reactions are classifEffects of medicinal products on the fetusDuring pregnancy, the developing organism is exceptionally vulnerable to the ePharmacist's algorithm of actions for side effectsThe algorithm of pharmacist actions upon detecting side effects (SE) isToxic action of medicinal productsThe toxic effect of drug substances develops when creating in Drug-induced dysbiosisDrug-induced dysbiosis is a pathological disruption of the natural balDrug allergyDrug allergy is an immune response of the body to pharmacologicNeurotropic agentsNeurotropic agents are a specialized group of medicinal pr

Frequently asked questions for this section

What is the «first-pass» effect?

This is the process of presystemic elimination (metabolism) of a drug in the liver, which it enters via the portal vein system immediately after absorption, before reaching the general systemic circulation.

Why do hydrophilic polar substances not penetrate the brain?

In the brain capillaries, endothelial cells are tightly apposed without forming intercellular clefts. Since hydrophilic molecules cannot dissolve in the lipid membrane and there are no pathways for their filtration, they cannot cross the blood-brain barrier.

Is ATP energy consumption required for passive diffusion?

No, this process occurs absolutely without the expenditure of ATP energy. The movement of molecules happens exclusively due to the physical concentration difference on both sides of the membrane.

What is the difference between non-ionized and ionized drug forms?

The non-ionized form is lipophilic and easily penetrates cell membranes (is absorbed). The ionized form is hydrophilic, does not cross membranes, but is readily excreted by the kidneys.

Why is the rate of active transport subject to a limit?

This is due to the property of saturability. The number of carrier proteins in the membrane is limited. When all their active sites are occupied by substrate binding, the transport system operates at maximum capacity, and a further increase in substance concentration will not accelerate the process.

What is the efflux system and why is it needed?

This is an evolutionarily developed mechanism of ATP-dependent removal of xenobiotics from cells. It protects sensitive tissues from the accumulation of toxic substances and lipophilic molecules. The main participant in this process is P-glycoprotein.

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