Introduction to Pharmacology/High School (Nurse)

Pharmacology deals with: For didactic reasons, we divide pharmacology into:
 * pharmacodynamics − the mechanisms and effects of drugs → what a drug does to an organism,
 * pharmacokinetics − the fate of drugs in the body (absorption, distribution, metabolism, excretion).


 * general pharmacology
 * special pharmacology

General pharmacology
Defines, on the basis of experiments, the generally valid laws manifested in the interaction between the organism and the pharmaceutical. Its knowledge is a prerequisite for understanding special pharmacology.

Special pharmacology
Classifies drugs in terms of pharmacodynamics. It studies the properties of drugs in their specific form. Examines and determines their pharmacokinetics.

Recipes
A set of basic provisions that must be followed when handling and creating a prescription.

Medicinal forms

 * more about on Medicinal forms

Drug Elimination

 * more about on Elimination of drugs
 * Determined by the chemical properties of the substance of interest.
 * → water-soluble substances can be eliminated relatively quickly by the kidneys (PNC)
 * → fat-soluble drugs are poorly excreted in urine → require transport binding to proteins (e.g. plasma albumin) that are not present in urine → lipophilic drugs require conversion to more hydrophilic metabolites, i.e. are biotransformed

Biotransformation - metabolism

 * Processes occurring predominantly in the liver that are mediated by a number of enzymes.
 * Two phases:
 * Phase I reactions → change in drug structure (oxidation, reduction, hydrolysis).
 * Enzymes of the cytochrome P450 family. A metabolite often retains some liposolubility.
 * Phase II reactions → conjugation reactions, such as binding to glucuronic acid, sulfuric acid, or glycine → metabolites with larger molecules and good water solubility to allow hepatic and renal elimination.

Excretion

 * I.e. the removal of a substance from the internal environment of the body.
 * It takes place mainly in the liver and kidneys, less significantly in the lungs, intestine, salivary and sweat glands, etc.
 * Binding during excretion by the liver is substrate specific, therefore drug-drug interactions may occur when multiple drugs are administered simultaneously.

Distribution

 * Means the penetration of the drug from the systemic circulation into the tissues.
 * The process of distribution is strongly influenced by the properties of the administered substance.
 * For example, highly lipophilic drugs rapidly penetrate barriers and therefore tend to rapidly escape from the circulation and concentrate in tissues.
 * Hydrophilic drugs are unable to penetrate barriers and remain predominantly in the blood or extracellular fluid (see below).

Volume of distribution - Vd

 * This quantity relates the dose administered to the concentration achieved:
 * more about on Mathematical description of pharmacokinetic processes

Receptors

 * Receptor mechanisms → the substance acts through a receptor, i.e. protein macromolecules with which it reacts and thereby induces a cellular response,
 * → when endogenous or exogenous regulatory substances interact, they trigger a series of events that manifest themselves as a phamacological effect.


 * Affinity - characterizes the ability of a substance to bind at a given concentration to a given receptor.
 * Intrinsic activity - the ability of an attractant to elicit an effect.
 * Agonist - binds to a receptor and produces an effect by interacting with it. (Full agonist = 100% effect)¨¨
 * Partial agonist - has little agonist effect when acting alone, competitively antagonizes their effect when acting with stronger agonists.


 * Antagonist - inhibits the effect of agonists but has no effect on its own.
 * Reversibly interacting antagonists are referred to as competitive antagonists (they have relatively high affinity but very low intrinsic activity).
 * Non-competitive antagonists either bind irreversibly to the receptor while having very low intrinsic activity or inhibit the signal transduction induced by the agonist.

Non-receptor mechanisms

 * Influenced by the chemical properties of substances or their interaction with other protein molecules, e.g. in body fluids.
 * These include:
 * Increase in substrate supply (e.g., used to treat Parkinson's disease),
 * administration of a false precursor (e.g., α-methylnoradrenaline instead of NA is formed at the terminals),
 * Blockade of bioactive substance degradation (e.g., inhibition of a Physostigmine leading to acetylcholine accumulation; also e.g., inhibition of MAO),
 * affecting DNA function (cytostatics),
 * action of antibiotics and chemotherapeutics (affecting metabolism and function of the micro-organism).

Doses

 * more about on Relationship between dose, plasma level and effect

Changes with repeated administration

 * more about on Tachyphylaxis
 * more about on Tolerance
 * After repeated administration, allergy may occur on immunological grounds.

Drug interactions

 * more about on Drug interactions