In pharmacology (and more specifically pharmacokinetics), absorption is the movement of a drug into the bloodstream. Pharmacology (in Greek: pharmacon (φάρμακον) meaning drug, and logos (λόγος) meaning science) is the study of how substances interact with living organisms to produce a change in function. ... Pharmacokinetics is a branch of pharmacology dedicated to the study of the time course of substances and their relationship with an organism or system. ...

Absorption involves several phases. First, the drug needs to be administered via some route of administration (oral, via the skin, etc.) and in a specific dosage form such as a tablet, capsule, and so on. In pharmacology and toxicology, a route of administration is the path by which a drug, fluid, poison or other substance is brought into contact with the body 1. ... Look up Mouth in Wiktionary, the free dictionary. ... In zootomy and dermatology, skin is an organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs. ... Common disk-shaped tablets A pharmacological tablet is a medicinal or other active substance mixed with binder powders and pressed into a tablet form. ... The word capsule (from the Latin capsula, a small box), has many similar meanings in English: In botany, a capsule is a type of dry fruit as in the poppy, iris, foxglove, etc. ...

In other situations, such as intravenous therapy, intramuscular injection, enteral nutrition and others, absorption is even more straight-forward and there is less variability in absorption and bioavailability is often near 100%. An intravenous drip in a hospital Intravenous therapy or IV therapy is the administration of liquid substances directly into a vein. ... Intramuscular injection is the injection of a substance directly into a muscle. ... In pharmacology, bioavailability is used to describe the fraction of an administered dose of medication that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. ...

Absorption is a primary focus in drug development and medicinal chemistry, since the drug must be absorbed before any medicinal effects can take place. Moreover, the drug's pharmacokinetic profile can be easily and significantly changed by adjusting factors that affect absorption. It has been suggested that this article or section be merged into Pharmacology. ... Medicinal or pharmaceutical chemistry is a scientific discipline at the intersection of chemistry and pharmacy involved with designing, synthesizing and developing pharmaceutical drugs. ...

Dissolution

In the most standard situation, a tablet is ingested and passes through the gullet to the stomach. Because the stomach is an aqueous environment, this is the first place where a tablet will dissolve. The esophagus (also spelled oesophagus/œsophagus), or gullet is the muscular tube in vertebrates through which ingested food passes from the mouth area to the stomach. ... In anatomy, the stomach (in ancient Greek στόμαχος) is an organ in the gastrointestinal tract used to digest food. ... Drinking water This article focuses on water as we experience it every day. ... Solvation is the attraction and association of molecules of a solvent with molecules or ions of a solute. ...

The rate of dissolution is a key target for controlling the duration of a drug's effect, and as such, several dosage forms that contain the same active ingredient may be available, differing only in the rate of dissolution. If a drug is supplied in a form that is not readily dissolved, the drug may be released more gradually over time with a longer duration of action. Having a longer duration of action may improve compliance since the medication will not have to be taken as often. Additionally, slow-release dosage forms may maintain concentrations within a acceptable therapeutic range over a long period of time, as opposed to quick-release dosage forms which may result in sharper peaks and troughs in serum concentrations. Compliance (or Adherence) in a medical context refers to a patient both agreeing to and then undergoing some part of their treatment program as advised by their doctor or other healthcare worker. ...

The rate of dissolution is described by the Noyes-Whitney equation as shown below: Arthur Amos Noyes (1866 – 1936) was a U.S. chemist and educator. ... Whitney as a MIT faculty member. ... An equation is a mathematical statement, in symbols, that two things are the same. ...

Where:

• is the rate of dissolution.
• A is the surface area of the solid.
• C is the concentration of the solid in the bulk dissolution medium.
• C_s is the concentration of the solid in the diffusion layer surrounding the solid.
• D is the diffusion coefficient.
• L is the diffusion layer thickness.

As can be inferred by the Noyes-Whitney equation, the rate of dissolution may be modified primarily by altering the surface area of the solid. The surface area may be adjusted by altering the particle size (e.g. micronization). The rate of dissolution may also be altered by choosing a suitable polymorph of a compound. Specifically, cystalline forms dissolve slower than amorphous forms. This article explains the meaning of area as a Physical quantity. ... This article or section does not cite its references or sources. ... In mathematics, a coefficient is a multiplicative factor of a certain object such as a variable (for example, the coefficients of a polynomial), a basis vector, a basis function and so on. ... Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. ...

Also, coatings on a tablet may act a barrier to reduce the rate of dissolution. Coating may also be used to modify where dissolution takes place. For example, enteric coatings may be applied to a drug, so that the coating only dissolves in the basic environment of the intestines. This will prevent release of the drug before reaching the intestines. An enteric coating is a barrier applied to oral medication that controls the location in the digestive system where it is absorbed. ... A bases in chemistry is a chemical substance which has a free pair of electrons to bind a Hydrogen ion commonly referred to as a proton (IUPAC definition). ...

Since solutions are already dissolved, they do not need to undergo dissolution before being absorbed.

Ionization

The gastrointestinal tract is lined with epithelial cells. Drugs must pass through these cells in order to be absorbed into the circulatory system. One particular cellular barrier that may prevent absorption of a given drug is the cell membrane. Cell membranes are essentially lipid bilayers which form a semipermeable membrane. Pure lipid bilayers are generally permeable only to small, uncharged solutes. Hence, whether or not a molecule is ionized will affect its absorption, since ionic molecules are considered charged molecules by definition. The gastrointestinal tract or digestive tract, also referred to as the GI tract or the alimentary canal, (nourishment canal) or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... Types of epithelium This article discusses the epithelium, an animal anatomical structure. ... The Circulatory System is a Psychedelic Rock musical ensemble formed by musician/painter Will Cullen Hart, and featuring Hannah Jones , Derek Almstead , Peter Erchick , John Fernandes , and Heather McIntosh. ... Drawing of a cell membrane A cell membrane, plasma membrane or plasmalemma is a selectively permeable lipid bilayer coated by proteins which comprises the outer layer of a cell. ... A diagonal molecular slab from the DPPC lipid bilayer simulation1; color scheme: PO4 - green, N(CH3)3 - violet, water - blue, terminal CH3 - yellow, O - red, glycol C - brown, chain C - grey. ... Scheme of semipermeable membrane during hemodialysis. ... ...

Due to the Henderson-Hasselbalch equation, drugs that are weak acids (such as aspirin) will be present mainly in their non-ionic form, and weak bases will be in their ionic form. Since non-ionic species diffuse more readily through cell membranes, weak acids will have a higher absorption in the highly-acidic stomach. The Henderson-Hasselbalch (frequently misspelled Henderson-Hasselbach) equation in chemistry describes the derivation of pH as a measure of acidity (using pKa, the acid dissociation constant) in biological and chemical systems. ... A weak acid is an acid that does not fully ionize in solution; that is, if the acid was represented by the general formula HA, then in aqueous solution a significant amount of undissolved HA still remains. ... Aspirin or acetylsalicylic acid (acetosal) is a drug in the family of salicylates, often used as an analgesic (against minor pains and aches), antipyretic (against fever), and anti-inflammatory. ... An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss (or addition) of an electron. ... Drawing of a cell membrane A cell membrane, plasma membrane or plasmalemma is a selectively permeable lipid bilayer coated by proteins which comprises the outer layer of a cell. ... In anatomy, the stomach (in ancient Greek στόμαχος) is an organ in the gastrointestinal tract used to digest food. ...

However, the reverse is true in the basic environment of the intestines-- weak bases (such as caffeine) will diffuse more readily since they will be non-ionic. A bases in chemistry is a chemical substance which has a free pair of electrons to bind a Hydrogen ion commonly referred to as a proton (IUPAC definition). ... Caffeine is a xanthine alkaloid compound that acts as a stimulant in humans. ...

This aspect of absorption has been targeted by medicinal chemistry. For example, a suitable analog may be chosen so that the drug is more likely to be in a non-ionic form. Also, prodrugs of a compound may be developed by medicinal chemists-- these chemical variants may be more readily absorbed and then metabolized by the body into the active compound. However, changing the structure of a molecule is less predictable than altering dissolution properties, since changes in chemical structure may affect the pharmacodynamic properties of a drug. An analog is in chemistry a chemical closely related to another usually sharing the same nucleus. ... A prodrug is a pharmacological substance (drug) which is administered in an inactive (or significantly less active) form. ... Pharmacodynamics is the study of the biochemical and physiological effects of drugs and the mechanisms of drug action and the relationship between drug concentration and effect. ...

Other factors

Absorption may be further influenced by gut motility, prior surgery to the intestines, simultaneous intake of food, other drugs, and many other factors. The intestine is the portion of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine. ... Motility is the ability to move spontaneously and independently. ... Intraoperative X-Ray of a Humerus fixated by Kirschner wires Surgery (from the Greek meaning hand work) is the medical specialty that treats diseases or injuries by operative manual and instrumental treatment. ... The intestine is the portion of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine. ...