Dose (biochemistry) in the context of "Toxicity"

Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (cytotoxicity) or an organ such as the liver (hepatotoxicity). Sometimes the word is more or less synonymous with poisoning in everyday usage.

A central concept of toxicology is that the effects of a toxicant are dose-dependent; even water can lead to water intoxication when taken in too high a dose, whereas for even a very toxic substance such as snake venom there is a dose below which there is no detectable toxic effect. Toxicity is species-specific, making cross-species analysis problematic. Newer paradigms and metrics are evolving to bypass animal testing, while maintaining the concept of toxicity endpoints.

An adverse effect is an undesired harmful 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. The term complication is similar to adverse effect, but the latter is typically used in pharmacological contexts, or when the negative effect is expected or common. If the negative effect results from an unsuitable or incorrect dosage or procedure, this is called a medical error and not an adverse effect. Adverse effects are sometimes referred to as "iatrogenic" because they are generated by a physician/treatment. Some adverse effects occur only when starting, increasing or discontinuing a treatment.Using a drug or other medical intervention which is contraindicated may increase the risk of adverse effects. Adverse effects may cause complications of a disease or procedure and negatively affect its prognosis. They may also lead to non-compliance with a treatment regimen. Adverse effects of medical treatment resulted in 142,000 deaths in 2013 up from 94,000 deaths in 1990 globally.

The harmful outcome is usually indicated by some result such as morbidity, mortality, alteration in body weight, levels of enzymes, loss of function, or as a pathological change detected at the microscopic, macroscopic or physiological level. It may also be indicated by symptoms reported by a patient. Adverse effects may cause a reversible or irreversible change, including an increase or decrease in the susceptibility of the individual to other chemicals, foods, or procedures, such as drug interactions.

The British National Formulary (BNF) is a United Kingdom (UK) pharmaceutical reference book that contains a wide spectrum of information and advice on prescribing and pharmacology, along with specific facts and details about many medicines available on the UK National Health Service (NHS). Information within the BNF includes indication(s), contraindications, side effects, doses, legal classification, names and prices of available proprietary and generic formulations, and any other notable points. Though it is a national formulary, it nevertheless also includes entries for some medicines which are not available under the NHS, and must be prescribed and/or purchased privately. A symbol clearly denotes such drugs in their entry.

It is used by pharmacists and doctors (both general practitioners (GPs) and generalist hospital practitioners) and by other prescribing healthcare professionals (such as nurses, pharmacy technicians, paramedics, and dentists); as a reference for correct dosage, indication, interactions and side effects of drugs. It is also used for reassurance by those administering drugs, for example a nurse on a hospital ward, and even for patients and others seeking an authoritative source of advice on any aspect of pharmacotherapy.

Dosage forms (also called unit doses) are pharmaceutical drug products presented in a specific form for use. They contain a mixture of active ingredients and inactive components (excipients), configured in a particular way (such as a capsule shell) and apportioned into a specific dose. For example, two products may both be amoxicillin, but one may come in 500 mg capsules, while another may be in 250 mg chewable tablets.

The term unit dose can also refer to non-reusable packaging, particularly when each drug product is individually packaged. However, the FDA differentiates this by referring to it as unit-dose "packaging" or "dispensing". Depending on the context, multi(ple) unit dose may refer to multiple distinct drug products packaged together or a single product containing multiple drugs and/or doses.

Dosing generally applies to feeding chemicals or medicines when used in small quantities.

For medicines the term dose is generally used. In the case of inanimate objects the word dosing is typical. The term dose titration, referring to stepwise adjustment of doses until a desired level of effect is reached, is common in medicine.

The dose–response relationship, or exposure–response relationship describes the magnitude of the response of a biochemical or cell-based assay or an organism, as a function of exposure (or doses) to a stimulus or stressor (usually a chemical) after a certain exposure time. Dose–response relationships can be described by dose–response curves, or concentration-response curves. This is explained further in the following sections. A stimulus response function or stimulus response curve is defined more broadly as the response from any type of stimulus, not limited to chemicals.

In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or pharmacophore but can be modified by the other constituents. Among the various properties of chemical compounds, pharmacological/biological activity plays a crucial role since it suggests uses of the compounds in the medical applications. However, chemical compounds may show some adverse and toxic effects which may prevent their use in medical practice.

Biological activity is usually measured by a bioassay and the activity is generally dosage-dependent, which is investigated via dose-response curves. Further, it is common to have effects ranging from beneficial to adverse for one substance when going from low to high doses. Activity depends critically on fulfillment of the ADME criteria. To be an effective drug, a compound not only must be active against a target, but also possess the appropriate ADME (Absorption, Distribution, Metabolism, and Excretion) properties necessary to make it suitable for use as a drug. Because of the costs of the measurement, biological activities are often predicted with computational methods, so-called QSAR models.