A dose is a quantity of something (chemical A chemical substance is a material with a specific chemical composition, physical, or biological Biology is the natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. The term biology in its modern sense appears to have been introduced independently by Karl Friedrich Burdach (1800), Gottfried Reinhold Treviranus (Biologie oder) that may impact an organism biologically; the greater the quantity, the larger the dose. In nutrition Nutrition is the provision, to cells and organisms, of the materials necessary (in the form of food) to support life. Many common health problems can be prevented or alleviated with a healthy diet, the term is usually applied to how much of a specific nutrient A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. Nutrients are the substances that enrich the body. They build and repair tissues, give heat and energy, and regulate body processes. Methods for nutrient intake vary, with animals and is in a person's diet or in a particular food, meal, or dietary supplement A dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to provide nutrients, such as vitamins, minerals, fiber, fatty acids or amino acids, that are missing or are not consumed in sufficient quantity in a person's diet. Some countries define dietary supplements as foods, while in others they are. In medicine Medicine is the art and science of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness, the term is usually applied to the quantity of a drug A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage or other agent administered for therapeutic Therapy , or treatment, is the attempted remediation of a health problem, usually following a diagnosis. In the medical field, it is synonymous with the word "treatment" purposes. In toxicology Toxicology is the study of the adverse effects of chemicals on living organisms. It is the study of symptoms, mechanisms, treatments and detection of poisoning, especially the poisoning of people dose may refer to the amount of a harmful agent (such as a poison In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism. Legally and in hazardous chemical labelling, poisons are especially toxic substances; less toxic substances are labelled ", carcinogen A carcinogen is any substance, radionuclide or radiation that is an agent directly involved in the exacerbation of cancer or in the increase of its propagation. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substances are considered carcinogens, but their carcinogenic, mutagen In biology, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are typically also carcinogens. Not all mutations are caused by mutagens: so-called "spontaneous, or teratogen Teratology is the study of abnormalities of physiological development. It is often thought of as the study of birth defects, but it is much broader than that, taking in other developmental stages, such as puberty; and other life forms, such as plants), to which an organism is exposed.

Chemicals are the most common things for which doses are measured, but there are others, such as radiation exposure. For humans, most doses of micronutrients Micronutrients are nutrients needed throughout life in small quantities. They are dietary minerals needed by the human body in very small quantities as opposed to macrominerals which are required in larger quantities. The Microminerals or trace elements include at least iron, cobalt, chromium, copper, iodine, manganese, selenium, zinc and and medications are measured in milligrams (mg.), but some are measured in micrograms In the metric system, a microgram is 1/1,000,000 of a gram (1 × 10–6), or 1/1000 of a milligram, is one of the smallest units of weight/mass commonly used. The abbreviation μg is often used in scientific literature, but JCAHO recommends that hospitals do not use this abbreviation in handwritten orders due to the risk that the Greek letter μ because of their potency. Nonmedicinal poisons span the measurement scale; some poisons are so dangerous that a single microgram of it could be deadly, while other substances take much more. For example, even water is toxic Water intoxication is a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside of safe limits by over-consumption of water. Normal, healthy (both physically and nutritionally) individuals have little reason to worry about accidentally consuming too much water. Nearly all when consumed in large enough quantities.

Effects are dose dependent

Dosage (the size of each dose Quantity is a kind of property which exists as magnitude or multitude. It is among the basic classes of things along with quality, substance, change, and relation. Quantity was first introduced as quantum, an entity having quantity. Being a fundamental term, quantity is used to refer to any type of quantitative properties or attributes of things) determines the strength and duration of the health benefits of nutrients, and also of the therapeutic effects A therapeutic effect is a consequence of a medical treatment of any kind, the results of which are judged to be desirable and beneficial. This is true whether the result was expected, unexpected, or even an unintended consequence of the treatment. An adverse effect, on the other hand, is a harmful and undesired effect of medical treatments. Dosage also determines the severity of adverse effects In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect, and may result from an unsuitable or incorrect dosage or procedure, which could be due to medical of treatments and toxins.

Duration Duration is an amount of time or a particular time interval. In sounds and music, a duration is a property of a tone that becomes one of the bases of rhythm of exposure, that is, the period of time over which the dose was received (all at once or gradually) also determines its effects (the body may build tolerance to gradual exposure to a drug, while a large immediate dose could be deadly).

The route Drug delivery is the method or process of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals. Drug delivery technologies are patent protected formulation technologies that modify drug release profile, absorption, distribution and elimination for the benefit of improving product efficacy and safety, as well by which a dose is exposed to, may affect the outcome, because some medications have different effects depending on whether they are inhaled Inhalation begins with the onset of contraction of the diaphragm, which results in expansion of the intrapleural space and an increase in negative pressure according to Boyle's Law. These negative pressure generates airflow because of the pressure difference between the atmosphere and alveolus. Air enters, inflating the lung through either the, ingested Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms, ingestion can take place through taking the substance through the cell wall, taken transdermally A transdermal patch or skin patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through the skin and into the bloodstream. Often, this promotes healing to an injured area of the body. An advantage of a transdermal drug delivery route over other types such as oral, topical, etc is that it provides, injected An injection is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body. An injection follows a parenteral route of administration, that is, administered other than through the digestive tract, or inserted A suppository is a drug delivery system that is inserted into the rectum , vagina (vaginal suppository), or urethra (urethral suppository), where it dissolves.

The dosage, route, concentration, and division over time may all be critical considerations in the administering of drugs, or in responding to exposure to a toxin. In nutrition, the route is usually a given, as nutrients are generally eaten; while dosage and the frequency of ingestion of nutrients are very important variables in preventing disease and promoting overall health.

Calculation of dose

Calculating drug dosages for humans based on the doses used in animal studies can be based on weight (eg. mg/kg) or surface area (eg. mg/m²) based on weight^2/3. ^[1] See also Body surface area In physiology and medicine, the body surface area is the measured or calculated surface of a human body. For many clinical purposes BSA is a better indicator of metabolic mass than body weight because it is less affected by abnormal adipose mass. Estimation of BSA is simpler than many measures of volume.

Biological agents

Biological agents (bacteria, viruses, parasites) may have different dosage units. This is because it is the ability of the organism to cause effects that is the important unit, not a specific quantity by weight, volume or even numerical count. Often the unit used is CFU (colony forming units), which is proportionate to the number of organisms present multiplied times the number able to reproduce on a culture medium such as a Petri dish.

Toxicology

In the realm of toxicology Toxicology is the study of the adverse effects of chemicals on living organisms. It is the study of symptoms, mechanisms, treatments and detection of poisoning, especially the poisoning of people, several measures are commonly used to describe toxic dosages according to the degree of effect on an organism or a population, and some are specifically defined by various laws or organizational usage. These include:

• LD50 = Median lethal dose In toxicology, the median lethal dose, LD50 , LC50 (Lethal Concentration, 50%) or LCt50 (Lethal Concentration & Time) of a toxic substance or radiation is the dose required to kill half the members of a tested population. LD50 figures are frequently used as a general indicator of a substance's acute toxicity. The test was created by J.W, a dose which will kill 50% of an exposed population;
• NOEL = No Observed Effect Level, the highest dose known to show no effect;
• NOAEL = No Observed Adverse Effect Level, the highest dose known to show no adverse effects;
• PEL = Personal Exposure Limit, the highest concentration permitted under US OSHA The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M Nixon, on December 29, 1970. Its mission is to prevent work-related injuries, illnesses, and occupational regulations;
• STEL = Short Term Exposure Limit, the highest concentration permitted for short periods of time, generally 15-30 minutes;
• TWA = Time Weighted Average, the average amount of an agent's concentration over a specified period of time, usually 8 hours;

References

1. ^ http://cancerres.aacrjournals.org/cgi/reprint/18/7/853.pdf "The Use of Body Surface Area as a Criterion of Drug Dosage in Cancer Chemotherapy" D Pinkel. Cancer Research 1958

Categories: Pharmacology Pharmacology (in Greek: pharmacon meaning drug, and logos (λόγος) meaning science) is the study of how chemical substances interact with living systems. If substances have medicinal properties, they are considered pharmaceuticals. The field encompasses drug composition and properties, interactions, toxicology, therapy, and medical | Toxicology Categories: Medical specialties | Ecology | Environmental science

See Also:

• Dose (Biochemistry)
• Effective Dose

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