Glycylcycline
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2008-05-28T13:03:26Z
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'''Glycylcyclines''' are a new class of antibiotics derived from [[tetracycline]]. These tetracycline analogues are specifically designed to overcome two common mechanisms of [[Tetracycline#Mechanism and resistance|tetracycline resistance]], namely resistance mediated by acquired [[Efflux (microbiology)|efflux pumps]] and/or ribosomal protection. Presently, there is only one glycylcycline antibiotic for clinical use: [[tigecycline]].
== History ==
The development of these agents was spurred by the increasing prevalence of bacteria resistant to tetracyclines. These agents were first synthesized in the early 1990's by making modifications to the tetracyclines. By adding a bulky N,N-dimethylglycylamido [[side chain]] to position 9 of [[minocycline]], the compound became less susceptible to tetracycline resistance mediated by acquired efflux pumps and/or ribosomal protection. Further development of this initial work led to the creation of [[tigecycline]], the first glycylcycline available for clinical use.
== Mechanism of Action ==
Glycylcycline antibiotics have a similar [[mechanism of action]] as tetracycline antibiotics. Both classes of antibiotics bind to the 30S [[Ribosome|ribosomal]] subunit to prevent the amino-acyl tRNA from binding to the A site of the ribosome. However, the glycylcyclines appear to bind more effectively than the tetracyclines [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8878615&query_hl=1].
== Mechanisms of Resistance ==
While glycylcyclines have greater efficacy against organisms with tetracycline resistance mediated by acquired efflux pumps and/or ribosomal protection, the glycylcyclines are not effective against organisms with chromosomal efflux pumps, such as ''[[Pseudomonas]]'' and Proteeae[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16120626&query_hl=3].
== Side Effects and Contraindications ==
Since glycylcyclines are similar to tetracyclines, they share many of the same side effects and contraindications as tetracyclines. These side effects may include nausea/vomiting, headache, [[photosensitivity]], discoloration of growing teeth, and fetal damage.
These antibiotics should not be given to pregnant women due to risk of fetal harm. Additionally, these drugs should not be administered during periods of tooth development because of the risk of tooth discoloration. Due to glycylcyclines' similarities with tetracyclines, hypersensitivity reactions to tetracycline antibiotics may predispose one to hypersensitivity reactions with glycylcycline antibiotics; hence, glycylcyclines should be used with caution in these patients.
== References ==
* [http://www.formularyjournal.com/formulary/article/articleDetail.jsp?id=177008 Tigecycline: A novel glycylcycline antiobiotic]. Aug 1, 2005. By: Kara L. Smith, BSc, Sarah M. McCabe, BSc, Jeffrey R. Aeschlimann, PharmD. ''Formulary''.
== External links ==
* [http://www.tygacil.com/ Tygacil (tigecycline IV) manufacturer website.]
* {{cite journal |author=Zhanel GG, Homenuik K, Nichol K, ''et al'' |title=The glycylcyclines: a comparative review with the tetracyclines |journal=Drugs |volume=64 |issue=1 |pages=63–88 |year=2004 |pmid=14723559 |doi=}}
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[[Category:Glycylcycline antibiotics|*]]
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