• Telithromycin packaged and labeled.

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SKU: T015

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Telithromycin (Ketek, HMR 3647, RU 66647) is a semisynthetic antibacterial agent belonging to a class of drugs called ketolides, which are a variation on the existing class of antibiotics known as macrolides like erythromycin, whose structure includes a 14-molecule ring. Telithromycin was developed by the French pharmaceutical company Roussel Uclaf S.A., prior to 1997. 

Telithromycin fulfills a role that has arisen due to the rise of microbial resistance to existing macrolides and appears to be effective against macrolide-resistant Streptococcus pneumoniae. The defining differentiating characteristic of the ketolides, as opposed to other macrolides, is the removal of the neutral sugar, L-cladinose from the 3-position of the macrolide ring and the subsequent oxidation of the 3-hydroxyl to a 3-keto functional group.

Telithromycin show activity against gram-positive and gram-negative bacteria, as well as mycoplasma.  Telithromycin is a bacterial protein synthesis inhibitor that interacts with peptidyl transferase site of the 50S ribosomal subunit.  The main binding sites are with domains II and V of the 23S rRNA.

Telithromycin is sparingly soluble in water (0.3 mg/mL) and has a solubility of approximately 30mg/ml in organic solvents such as DMSO, ethanol, and dimethyl formamide (should be purged with inert gas).

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    Mechanism of Action

    Telithromycin is a very effective inhibitor of the translation function at the level of the 50S ribosomal subunit. It has been shown that 14‐ and 15‐membered ring macrolides are also able to inhibit a second cellular function, the assembly of the nascent 50S ribosomal subunit. Telithromycin, in addition, like many carbamate ketolides, is also able to inhibit the formation of the 30S ribosomal subunit.

    23S rRNA is composed of six domains. Domains V and II belong partly to the peptidyl transferase site, and erythromycin A interacts mainly with domain V.

    Telithromycin, like 14‐ and 15‐membered ring macrolides, interacts with the bacterial 23S rRNA. Interactions are limited to a region of domain V and additionally, for telithromycin, to domain II. The interaction with the 750 loop (position A‐752) of domain II is due to the C11–C12 carbamate chain.

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    Telithromycin shows activity against gram-positive and gram-negative bacteria, as well as mycoplasma. More specifically, Telithromycin retains its activity against erm-(MLS(B)) or mef-mediated macrolide-resistant Streptococcus pneumoniae and Streptococcus pyogenes and against Staphylococcus aureus resistant to macrolides through inducible MLS(B) mechanisms. Telithromycin also possesses high activity against the Gram-negative pathogens Haemophilus influenzae and Moraxella catarrhalis, regardless of beta-lactamase production. In vitro, it shows similar activity to azithromycin against H. influenzae, while in vivo its activity against H. influenzae is higher than that of azithromycin. Telithromycin's spectrum of activity also extends to the atypical, intracellular and cell-associated pathogens Legionella pneumophila, Mycoplasma pneumoniae and Chlamydia pneumoniae.


    Microbiology Applications

    Telithromycin is commonly used in clinical in vitromicrobiological antimicrobial susceptibility tests (panels, discs, and MIC strips) against gram positive microbial isolates. Medical microbiologists use AST results to recommend antibiotic treatment options for infected patients. Representative MIC values include:

    • Streptococcus pneumoniae 0.003 µg/mL – 0.5 µg/mL
    • Streptococcus pyogenes 0.015 µg/mL - 4 µg/mL
    • For a complete list of telithromycin MIC values, click here.





    White or off-white crystalline powder



    Water Content (Karl Fischer)

    Not more than 3.0%


    (HPLC, As Is): Not less than 98.0%



    Lovmar, Martin, and Tanel Tenson. "The Mechanism of Action of Macrolides, Lincosamides and Streptogramin B Reveals the Nascent Peptide Exit Path in the Ribosome."Journal of Molecular Microbiology 330.5 (2003): 1005-014.

    Telithromycin in the treatment of pneumococcal community-acquired respiratory tract infections: a review: C.M. Fogarty, et al.; Int. J. Infect. Dis. 10, 136 (2006)

    Felmingham, D., Zhanel, G., and Hoban, D. Activity of the ketolide antibacterial telithromycin against typical community-acquired respiratory pathogens. Journal of Antimicrobial Chemotherapy 48(Topic T1), 33-42 (2001).

    Hansen, L.H., Mauvais, P., and Douthwaite, S. The macrolide-ketolide antibiotic binding site is formed by structures in domains II and V of 23S ribosomal RNA. Molecular Microbiology 31(2), 623-631 (1999).

    The ketolide antibiotics HMR-3647 and HMR 3004 are active against Toxoplasma gondii in vitro and in murine models of infection: F.G. Araujo, et al.; Antimicrob. Agents Chemother. 41, 2137 (1997)

    The in-vitro activity of HMR 3647, a new ketolide antimicrobial agent: F.J. Boswell, et al.; J. Antimicrob. Chemother. 42, 703 (1998)

    Drugs of the 21st century: telithromycin (HMR 3647) - the first ketolide: G. Ackermann & A.C. Rodloff; J. Antimicrob. Chemother. 51, 497 (2003)

    Telithromycin: K. Wellington & S. Noble; Drugs 64, 1683 (2004)

    Telithromycin: A ketolide antibiotic for treatment of respiratory tract infections: J.R. Lonks & D.A. Goldmann; Clin. Inf. Dis. 40, 1657 (2005)

    Antibacterial drug discovery-Then, now and the genomics future: R. Monaghan & J.F. Barrett; Biochem. Pharmacol. 71, 901 (2006)

    Benefit-risk assessment of telithromycin in the treatment of community-acquired pneumonia: S.D. Brown; Drug Safety 31, 561 (2008)

    Time-dependent effects of Klebsiella pneumonia endotoxin on the telithromycin pharmacokinetics in rats; restoration of the parameters in 96-hour KPLPS rats to the control levels: J.H. Lee, et al.; Pulm. Pharmacol. Ther. 21, 860 (2008)

    Ketolides - the modern relatives of macrolides: the pharmacokinetic perspective: M. Zeitlinger, et al.; Clin. Pharmacokinet. 48, 23 (2009)

    Inducible expression of erm(B) by the ketolides telithromycin and cethromycin: P. Byoungduck & M. Yu-Hong; Int. J. Antimicrob. Agents 46, 226 (2015)

    ClpP-independent function of ClpX interferes with telithromycin resistance conferred by msr(A) in Staphylococcus aureus: V. Vimberg, et al.; Antimicrob. Agents Chemother. 59, 3611 (2015)

    Douthwaite, S., and Champney, W.S. Structures of ketolides and macrolides determine their mode of interaction with the ribosomal target site. Journal of Antimicrobial Chemotherapy 48 (Topic T1), 1-8 (2001).

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