Editing Racemic mixture (section)

==Racemic pharmaceuticals==
{{see also|Enantiopure drug}}

Some [[Small molecule|drug molecules]] are chiral, and the enantiomers have different effects on biological entities. They can be sold as one enantiomer or as a racemic mixture. Examples include [[thalidomide]], [[ibuprofen]], [[cetirizine]] and [[salbutamol]]. A well known drug that has different effects depending on its ratio of enantiomers is [[amphetamine]]. [[Adderall]] is an unequal mixture of both [[amphetamine]] enantiomers. A single Adderall dose combines the neutral sulfate salts of [[dextroamphetamine]] and amphetamine, with the dextro isomer of amphetamine saccharate and D/L-amphetamine aspartate monohydrate. The original [[Benzedrine]] was a racemic mixture, and isolated dextroamphetamine was later introduced to the market as Dexedrine. The prescription analgesic [[tramadol]] is also a racemate.

In some cases (e.g., [[ibuprofen]] and [[thalidomide]]), the enantiomers interconvert or [[racemize]] ''[[in vivo]]''. This means that preparing a pure enantiomer for medication is largely pointless. However, sometimes samples containing pure enantiomers may be made and sold at a higher cost in cases where the use requires specifically one isomer (e.g., for a [[stereospecific]] reagent); compare [[omeprazole]] and [[esomeprazole]]. Moving from a racemic drug to a chiral specific drug may be done for a better safety profile or an improved therapeutic index. This process is called '''chiral switching''' and the resulting enantiopure drug is called a [[chiral switch]].<ref>{{cite journal |last1=Agranat |first1=Israel |last2=Wainschtein |first2=Silvya R. |title=The strategy of enantiomer patents of drugs |journal=Drug Discovery Today |date=March 2010 |volume=15 |issue=5–6 |pages=163–170 |doi=10.1016/j.drudis.2010.01.007 |pmid=20116449 }}</ref> As examples, [[esomeprazole]] is a chiral switch of  (±)-omeprazole and [[levocetirizine]] is a chiral switch of (±)-cetirizine.

While often only one enantiomer of the drug may be active, there are cases in which the other enantiomer is harmful, like [[salbutamol]]<ref>{{cite journal |last1=Ameredes |first1=Bill T. |last2=Calhoun |first2=William J. |title=(R)-Albuterol for Asthma: Pro [a.k.a. (S)-Albuterol for Asthma: Con] |journal=American Journal of Respiratory and Critical Care Medicine |date=November 2006 |volume=174 |issue=9 |pages=965–969 |doi=10.1164/rccm.2606001 |pmid=17060667 }}</ref> and [[thalidomide]]. The (R) enantiomer of thalidomide is effective against morning sickness, while the (S) enantiomer is teratogenic, causing birth defects. Since the drug racemizes, the drug cannot be considered safe for use by women of child-bearing age,<ref>{{cite journal |last1=de Jesus |first1=Soraya Machado |last2=Santana |first2=Rafael Santos |last3=Leite |first3=Silvana Nair |title=Comparative analysis of the use and control of thalidomide in Brazil and different countries: is it possible to say there is safety? |journal=Expert Opinion on Drug Safety |date=2 January 2022 |volume=21 |issue=1 |pages=67–81 |doi=10.1080/14740338.2021.1953467 |pmid=34232089 |s2cid=235759079 }}</ref> and its use is tightly controlled when used for treating other illness.<ref name="nyt-fda">{{cite news |last1=Stolberg |first1=Sheryl Gay |title=Thalidomide Approved to Treat Leprosy, With Other Uses Seen |url=https://www.nytimes.com/1998/07/17/us/thalidomide-approved-to-treat-leprosy-with-other-uses-seen.html |work=The New York Times |date=17 July 1998 }}</ref>

[[Methamphetamine]] is available by prescription under the brand name [[Desoxyn]]. The active component of Desoxyn is [[dextromethamphetamine (medical)|dextromethamphetamine hydrochloride]]. This is the right-handed isomer of methamphetamine. The left-handed isomer of methamphetamine, [[levomethamphetamine]], is an [[Over-the-counter drug|OTC]] drug that is less centrally-acting and more peripherally-acting. Methedrine during the 20th century was a 50:50 racemic mixture of both methamphetamine isomers (levo and dextro).