Telithromycin is a semisynthetic ketolide antibacterial API structurally related to the macrolide antibiotic family. It was developed as a derivative of erythromycin and incorporates structural modifications intended to provide activity against selected respiratory pathogens, including certain macrolide-resistant Streptococcus pneumoniae. The marketed pharmaceutical product is associated with the brand Ketek. FDA describes telithromycin as a ketolide antibacterial for oral administration.
Telithromycin has the molecular formula C43H65N5O10 and molecular weight approximately 812.03 g/mol. FDA describes the substance as a white to off-white crystalline powder. The commonly listed CAS number is 191114-48-4, while an FDA chemistry review also records 173838-31-8 in its chemical-identity documentation.
Telithromycin is a chemically complex macrolide-derived antibacterial containing a ketolide 3-keto functionality and a substituted C11–C12 carbamate side chain containing imidazole and pyridine groups. These structural modifications distinguish telithromycin from conventional macrolides.
The API is a small-molecule pharmaceutical active ingredient intended for antibacterial pharmaceutical development and manufacturing. Commercial and research specifications describe the material as a white to off-white crystalline powder.
Telithromycin is chemically derived from erythromycin and belongs to the ketolide class. Removal of the α-L-cladinose group at position 3 produces the characteristic 3-keto functionality. The molecule also contains a carbamate substituent and a side chain incorporating pyridyl-imidazole functionality.
Its molecular formula is C43H65N5O10, with a molecular weight of 812.03 g/mol. PubChem reports approximately 13 defined stereocenters, reflecting the complex stereochemical architecture of the macrolide framework.
Telithromycin inhibits bacterial protein synthesis by binding to bacterial ribosomal RNA. FDA describes binding to domains II and V of the 23S rRNA component of the 50S ribosomal subunit. This interferes with bacterial protein synthesis and contributes to antibacterial activity.
The binding profile of telithromycin provides activity against certain Gram-positive respiratory pathogens, including Streptococcus pneumoniae. Its interaction with multiple ribosomal regions was developed in part to retain activity against organisms carrying certain macrolide-resistance mechanisms.
Telithromycin API is primarily associated with antibacterial pharmaceutical development and oral dosage forms.
Historically, telithromycin tablets were marketed in 300 mg and 400 mg strengths. FDA's labeling identifies telithromycin as a ketolide antibacterial intended for oral administration.
Pharmaceutical applications include:
Telithromycin requires comprehensive analytical control because of its complex molecular structure and multiple stereochemical centers. Suitable quality-control testing can include identity, assay, related substances, water or moisture, inorganic residue, residual solvents and other applicable pharmaceutical quality attributes.
FDA chemistry documentation identifies telithromycin as a chemically defined drug substance and provides its molecular identity and structural information. Published analytical research has also demonstrated stability-indicating liquid chromatographic methods capable of separating telithromycin from degradation products.
A published stability-indicating LC method reported a detection limit of 0.0027 μg/mL and quantification limit of 0.0082 μg/mL. These are analytical-method performance characteristics and must not be presented as API release specifications.
Telithromycin is manufactured through a semisynthetic process based on the macrolide/erythromycin structural framework, followed by chemical modification, purification and isolation of the final active ingredient.
Manufacturing controls should address:
The final pharmaceutical API should be released against a validated specification appropriate to the intended regulatory market.
FDA confirms the molecular formula, molecular weight and crystalline appearance, while PubChem reports the experimental melting-point and solubility data.
Published data describe telithromycin as sparingly soluble in water. PubChem reports an experimental solubility value of approximately 300 mg/L, equivalent to approximately 0.30 mg/mL. Other chemical-reference sources describe limited solubility in water and slight solubility in solvents such as methanol, DMSO and chloroform.
The 300 mg/L value should be regarded as a physicochemical reference value and not as a pharmaceutical release specification.
Telithromycin API should be stored in suitable pharmaceutical-grade, well-closed containers that protect the material from moisture, contamination and unsuitable environmental exposure.
Published commercial material specifications report storage conditions ranging from 2–8°C to −20°C, depending on the material grade and supplier. Therefore, the storage condition for pharmaceutical API should be established from the manufacturer's validated stability data and applicable specification rather than using a generic research-material storage condition.
Pharmaceutical-grade Telithromycin API documentation may include:
Telithromycin is a structurally complex ketolide API requiring consistent control of assay, related substances, moisture, inorganic residues and physical characteristics. A quality-focused manufacturing process should employ validated chromatographic and spectroscopic analytical procedures and appropriate pharmaceutical quality systems.
For pharmaceutical development and commercial manufacturing, Telithromycin API should be supplied according to the applicable customer, pharmacopoeial and regulatory requirements, with complete analytical documentation and batch-specific quality data.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.2% |
| Heavy Metals | NMT 10 ppm |
| Individual Impurity | NMT 0.5% |
| Total Impurities | ≤ 1.5% |
| Water Content | NMT 1.0% |