ParacetamoloSe pensa che una qualsiasi di tachipirina antinfiammatorio non steroideo condizioni La riguarda, non prenda queste compresse prima di aver consultato il medico. Informi il medico o il tachipirina antinfiammatorio non steroideo se sta assumendo, ha recentemente assunto o potrebbe assumere qualsiasi altro medicinale, inclusi quelli acquistabili senza ricetta del medico. In caso di gravidanza o di sospetta gravidanza, o se Lei pensa di poter rimanere incinta, non prenda le compresse. Se resta incinta, smetta di prendere le compresse e consulti il medico. Non utilizzi attrezzi o macchinari se avverte capogiro o sonnolenza. Prenda questo medicinale seguendo sempre esattamente le istruzioni del medico.
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Il paracetamolo fu sintetizzato per la prima volta nel da Harmon Northrop Morse per riduzione di p -nitrofenolo con stagno in acido acetico glaciale, secondo la seguente reazione.
Inizialmente si usavano acetanilide e fenacetina , derivati dell' anilina , come antipiretici di elezione, ma essi avevano forti conseguenze tossiche sul paziente. Era quindi il paracetamolo la sostanza che realmente determinava l' analgesia e il calo della temperatura. Quando una sostanza farmacologicamente attiva si origina, come nel caso del paracetamolo, in seguito all'assunzione di un altro prodotto l'acetanilide o la fenacetina , questo prodotto viene indicato come precursore , mentre la sostanza che si forma viene detta metabolita attivo.
Il paracetamolo era dunque il metabolita attivo sia dell'acetanilide, sia della fenacetina. Dal il paracetamolo ha iniziato ad essere usato come farmaco.
Si pensa Graham GG, Scott KF che l'azione antinfiammatoria sia attribuibile ad un'inibizione debole della via di sintesi delle prostaglandine. Al di fuori dell'inibizione della COX-1, sembra che esista una terza isoforma di ciclo-ossigenasi espressa a livello cerebrale COX-3 che potrebbe essere il bersaglio preferenziale del paracetamolo e di altri antipiretici. Per questo motivo, il dosaggio giornaliero massimo raccomandato negli alcolisti non deve superare i 2,5 grammi al giorno.
Il paracetamolo viene metabolizzato dalle cellule della zona 3 dell' acino epatico. Studi clinici effettuati sull'uomo non hanno evidenziato effetti teratogeni o fetotossici.
Secondo un piccolo numero di studi l'impiego del paracetamolo in gravidanza potrebbe essere associato ad un rischio ridotto di aborto e nascita pre-termine.
SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules, the original SMILES specification was initiated in the s.
It has since modified and extended. It has since modified and extended by others, most notably by Daylight Chemical Information Systems. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database, there is currently no systematic comparison across commercial software to test if such flaws exist in those packages.
In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases.
Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics.
Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka.
As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume.
As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.
In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density. The solubility of a substance depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure. The solubility of a substance is a different property from the rate of solution.
Most often, the solvent is a liquid, which can be a substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas, the extent of solubility ranges widely, from infinitely soluble such as ethanol in water, to poorly soluble, such as silver chloride in water. The term insoluble is often applied to poorly or very poorly soluble compounds, a common threshold to describe something as insoluble is less than 0. Under certain conditions, the solubility can be exceeded to give a so-called supersaturated solution.
Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its form or particle size. A supersaturated solution generally crystallises when seed crystals are introduced and rapid equilibration occurs, phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point.
Solubility is not to be confused with the ability to dissolve a substance, for example, zinc dissolves in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid, the smaller a particle is, the faster it dissolves although there are many factors to add to this generalization.
Crucially solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic, in all cases it will depend on the physical conditions and the enthalpy and entropy directly relating to the solvents and solutes concerned.
By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a range of organic substances. According to the IUPAC definition, solubility is the composition of a saturated solution expressed as a proportion of a designated solute in a designated solvent. Solubility may be stated in units of concentration such as molarity, molality, mole fraction, mole ratio, mass per volume.
Solubility occurs under dynamic equilibrium, which means that solubility results from the simultaneous and opposing processes of dissolution, the solubility equilibrium occurs when the two processes proceed at a constant rate. The term solubility is used in some fields where the solute is altered by solvolysis.
Acqua — Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms.
Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It is vital for all forms of life. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals.
Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by more than half of the population will be facing water-based vulnerability. A report, issued in November , suggests that by , in developing regions of the world.
Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes.
Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life.
Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of Metabolismo — Metabolism is the set of life-sustaining chemical transformations within the cells of living organisms. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, usually, breaking down releases energy and building up consumes energy. The chemical reactions of metabolism are organized into metabolic pathways, in one chemical is transformed through a series of steps into another chemical.
Enzymes act as catalysts that allow the reactions to proceed more rapidly, enzymes also allow the regulation of metabolic pathways in response to changes in the cells environment or to signals from other cells. The metabolic system of a particular organism determines which substances it will find nutritious, for example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals.
The speed of metabolism, the rate, influences how much food an organism will require. A striking feature of metabolism is the similarity of the metabolic pathways.
These striking similarities in metabolic pathways are likely due to their appearance in evolutionary history.
Most of the structures that make up animals, plants and microbes are made from three classes of molecule, amino acids, carbohydrates and lipids. These biochemicals can be joined together to make such as DNA and proteins. Proteins are made of amino acids arranged in a linear chain joined together by peptide bonds, many proteins are enzymes that catalyze the chemical reactions in metabolism.
Other proteins have structural or mechanical functions, such as those that form the cytoskeleton, Proteins are also important in cell signaling, immune responses, cell adhesion, active transport across membranes, and the cell cycle. Lipids are the most diverse group of biochemicals and their main structural uses are as part of biological membranes both internal and external, such as the cell membrane, or as a source of energy.
Lipids are usually defined as hydrophobic or amphipathic biological molecules but will dissolve in organic solvents such as benzene or chloroform, the fats are a large group of compounds that contain fatty acids and glycerol, a glycerol molecule attached to three fatty acid esters is called a triacylglyceride.
Several variations on this structure exist, including alternate backbones such as sphingosine in the sphingolipids. Steroids such as cholesterol are another class of lipids.
Carbohydrates are aldehydes or ketones, with hydroxyl groups attached. Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of energy, the basic carbohydrate units are called monosaccharides and include galactose, fructose, and most importantly glucose. Escrezione — Excretion is the process by which metabolic wastes and other non-useful materials are eliminated from an organism. In vertebrates this is carried out by the lungs, kidneys.
This is in contrast with secretion, where the substance may have specific tasks after leaving the cell, excretion is an essential process in all forms of life. For example, in urine is expelled through the urethra. In unicellular organisms, waste products are discharged directly through the surface of the cell, green plants produce carbon dioxide and water as respiratory products. In green plants, the carbon dioxide released during respiration gets utilized during photosynthesis, oxygen is a by product generated during photosynthesis, and exits through stomata, root cell walls, and other routes.
Plants can get rid of water by transpiration and guttation. These latter processes do not need added energy, they act passively, however, during the pre-abscission phase, the metabolic levels of a leaf are high. Plants also excrete some waste substances into the soil around them, in animals, the main excretory products are carbon dioxide, ammonia, urea, uric acid, guanine and creatine.
The liver and kidneys clear many substances from the blood, aquatic animals usually excrete ammonia directly into the external environment, as this compound has high solubility and there is ample water available for dilution. In terrestrial animals ammonia-like compounds are converted into other materials as there is less water in the environment.
Birds excrete their nitrogenous wastes as uric acid in the form of a paste and this is metabolically more expensive, but allows more efficient water retention and it can be stored more easily in the egg.
Many avian species, especially seabirds, can also excrete salt via specialized nasal salt glands, in insects, a system involving Malpighian tubules is utilized to excrete metabolic waste. Metabolic waste diffuses or is actively transported into the tubule, which transports the wastes to the intestines, the metabolic waste is then released from the body along with fecal matter. The excreted material may be called dejecta or ejecta, in pathology the word ejecta is more commonly used.
Simboli di rischio chimico — Hazard symbols or warning symbols are recognisable symbols designed to warn about hazardous materials, locations, or objects, including electric currents, poisons, and radioactivity. The use of symbols is often regulated by law and directed by standards organisations. Hazard symbols may appear different colors, backgrounds, borders and supplemental information in order to specify the type of hazard.
Warning symbols are used in places in lieu of or addition to written warnings as they are quickly recognized. On roadside warning signs, a mark is often used to draw attention to a generic warning of danger, hazards.