Editing Therapeutic index (section)

==Maximum tolerated dose==
The '''maximum tolerated dose''' (MTD) refers to the highest dose of a radiological or [[pharmacological agent|pharmacological]] treatment that will produce the desired effect without unacceptable [[toxicity]].<ref>{{cite web |publisher= National Cancer Institute |access-date=26 July 2010|url=http://www.cancer.gov/dictionary/?CdrID=546597 |title=maximum tolerated dose |work=Dictionary of Cancer Terms}}</ref><ref>{{CRS|article = Report for Congress: Agriculture: A Glossary of Terms, Programs, and Laws, 2005 Edition|url = http://ncseonline.org/nle/crsreports/05jun/97-905.pdf|author= Jasper Womach}}</ref> The purpose of administering MTD is to determine whether long-term exposure to a chemical might lead to unacceptable [[adverse health effect]]s in a population, when the level of exposure is not sufficient to cause premature [[mortality rate|mortality]] due to short-term [[toxic effect]]s. The maximum dose is used, rather than a lower dose, to reduce the number of [[human subjects research|test subjects]] (and, among other things, the cost of testing), to detect an effect that might occur only rarely. This type of analysis is also used in establishing [[chemical residue]] tolerances in foods. Maximum tolerated dose studies are also done in [[clinical trials]].

MTD is an essential aspect of a drug's profile. All modern healthcare systems dictate a maximum safe dose for each drug, and generally have numerous safeguards (e.g. insurance quantity limits and government-enforced maximum quantity/time-frame limits) to prevent the prescription and dispensing of quantities exceeding the highest dosage which has been demonstrated to be safe for members of the general patient population.

Patients are often unable to tolerate the theoretical MTD of a drug due to the occurrence of side-effects which are not innately a manifestation of toxicity (not considered to severely threaten a patient's health) but cause the patient sufficient distress and/or discomfort to result in non-compliance with treatment. Such examples include emotional "blunting" with antidepressants, [[pruritus]] with [[opiates]], and blurred vision with [[anticholinergics]].