Dose (biochemistry)

Dose (biochemistry)

A dose is a quantity of something (chemical, physical, or biological) that may impact an organism biologically; the greater the quantity, the larger the dose. In nutrition, the term is usually applied to how much of a specific nutrient is in a person's diet or in a particular food, meal, or dietary supplement. In medicine, the term is usually applied to the quantity of a drug or other agent administered for therapeutic purposes. In toxicology dose may refer to the amount of a harmful agent (such as a poison, carcinogen, mutagen, or teratogen), 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 and medications are measured in milligrams (mg), but some are measured in micrograms because of their potency. Nonmedicinal poisons span the measurement scale; some poisons are so dangerous that a single microgram of it could be deadly, whereas other substances take much more. For example, even water is toxic when consumed in large enough quantities.

Contents

Effects are dose-dependent

See also: The dose makes the poison

Dosage (the size of each dose) determines the strength and duration of the health benefits of nutrients, and also of the therapeutic effects of medical treatments. Dosage also determines the severity of adverse effects of treatments and toxins.

Duration 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 by which a dose is exposed to, may affect the outcome, because some medications have different effects depending on whether they are inhaled, ingested, taken transdermally, injected, or inserted.

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 (e.g., mg/kg) or surface area (e.g., mg/m2) based on weight2/3.[1] See also Body surface area. Desirable dosages may also vary *among* humans according to body weight and other factors.

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, 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, a dose that 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 regulations
  • STEL = Short-Term Exposure Limit, the highest concentration permitted for short periods of time, in general 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

Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • Dose — means quantity in the following fields: In nutrition, medicine, and toxicology: Dose (biochemistry), the quantity of something that may be eaten by or administered to an organism, or that an organism may be exposed to Medicine and toxicology… …   Wikipedia

  • Dose-response relationship — Semi log plots of two agonists with different Kd. The dose response relationship, or exposure response relationship, describes the change in effect on an organism caused by differing levels of exposure (or doses) to a stressor (usually a… …   Wikipedia

  • Copper in health — Normal absorption and distribution of copper. Cu = copper, CP = ceruloplasmin, green = ATP7B carrying copper. Copper is an essential trace element that is vital to the health of all living things (humans, plants, animals, and microorganisms). In… …   Wikipedia

  • Antioxidant — Model of the antioxidant metabolite glutathione. The yellow sphere is the redox active sulfur atom that provides antioxidant activity, while the red, blue, white, and dark grey spheres represent oxygen, nitrogen, hydrogen, and carbon atoms,… …   Wikipedia

  • Heparin — Systematic (IUPAC) name see Hep …   Wikipedia

  • pharmaceutical industry — Producers of pharmaceuticals, substances used in the diagnosis, treatment, and prevention of disease and the modification of organic functions. The earliest records of medicinal plants and minerals are those of the ancient Chinese, Hindu, and… …   Universalium

  • Vitamin C — This article is about ascorbic acid as a nutrient; for its chemical properties, see the article ascorbic acid; for other uses, see the disambiguation page. Vitamin C …   Wikipedia

  • Gundu Hirisave Rama Rao — was born in Tumkur (Karnataka), India, on 23 August 1937. He is a scientist, entrepreneur and a tenured professor at the Academic Health Center, University of Minnesota. He and Professor John Eaton visited India in 1981 under a National Science… …   Wikipedia

  • Dimethyltryptamine — Systematic (IUPAC) name 2 (1H indol 3 yl) N …   Wikipedia

  • Lovastatin — Systematic (IUPAC) name (1S,3R,7S,8S …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”