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== Up-and-down procedure ==

The '''Up-and-down procedure''' (pronunciation: /ʌp ænd daʊn prəˈsiːdʒər/) is a method used in [[pharmacology]] and [[anesthesiology]] to determine the [[median effective dose]] (ED50) or the [[median lethal dose]] (LD50) of a drug. The procedure is also known as the '''Dixon's up-and-down method''' after its developer, W.J. Dixon.

=== Etymology ===

The term "up-and-down procedure" is derived from the method's process, which involves increasing (up) or decreasing (down) the dosage of a drug based on the response of the previous subject. The term was first used in this context by W.J. Dixon in 1965.

=== Procedure ===

The up-and-down procedure begins with the administration of a drug at a certain dose to a subject. If the subject shows a positive response, the dose is decreased (down) for the next subject. If the subject shows a negative response, the dose is increased (up) for the next subject. This process is repeated until a dose is found that produces a positive response in 50% of the subjects, which is the ED50 or LD50.

=== Related Terms ===

* [[Dose-response relationship]]: The relationship between the dose of a drug and the response it produces.
* [[Therapeutic index]]: The ratio of the toxic dose to the therapeutic dose of a drug.
* [[Pharmacodynamics]]: The study of the biochemical and physiological effects of drugs and their mechanisms of action.
* [[Pharmacokinetics]]: The study of how a drug is absorbed, distributed, metabolized, and excreted by the body.

[[Category:Pharmacology]]
[[Category:Anesthesiology]]
[[Category:Medical terminology]]

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