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Developed in the late 1970’s Azithromycin is Azithromycin shows good retention in a sim- still one of the worlds most popular antibiot- ple isocratic mobile phase system, the high ics1. Present on the WHO’s (World Health Or- pH/high organic mobile phase system mean- ganisations) Essential Medicines Library, due ing that the compounds stays in solution well in part to the clinical efficacy of single dose and also gives good sensitivity, meeting the azithromycin2. Used to treat certain bacterial requirements of the various monograph com- infections, concerned mainly with ear infec- pendial methods. The variety of its structure tion, troat, pneumonia, typhoid and sinusitis. It m leads to difficulty if other lower pH reversed- is derived from Erthromycin a macrolide anti- bacterial compound, differing in that a methyl substituted nitrogen atom is incorporated into the lactone ring, thus making the lactone ring FortisTM C18 allows for good retention, sen- 15 membered. Azithromycin interfer’s with sitivity and selectivity of Azithromycin. The the protein synthesis of bacteria’s growth method developed allows for the simple use mechanism3. Pliva is the original developer of mobile phase conditions which are com- of Azithromycin in Crotia and in 1981 they 0 . 00 2 . 0 0 5 6 . 0 0 1100 . 0 0 1 4 . 1050 1 8 . 0 0 20 2 2 . 0 0 25 2 6 . 0 0 330.00 patible with todays most sensitive detection patented the drug, and sell under the name suspect in water hence high concentrations of technologies, Mass Spectroscopy and ELSD Sumamed in Europe, whilst Pfizer sells the organic solvent are general y preferred. In the (Light Scattering Detector).
licensed product under the name Zithromax. Ph.Eur. monograph potassium phosphate is Azithromycin is a popular drug with great In 2005 the patent ran out so now azithromy- used to provide this increased pH level. Unfor- proliferation, by having this simple analysis cin is manufactured as a generic drug mak- tunately not many columns wil handle these method for QC and a highly stable column ing it widely available at a competitive price.
then robustness and reproducibility can be In this application note FortisTM C18 was used assured.
since it can provide analysis at high pH upto pH 12. Typical y C18 columns wil not operate at these higher pH values. Fortis C18’s opti- mised bonding al ows for excel ant stbility and 1. http://www.wipo.int/sme/en/case_stud- lifetime at high pH. An ammonia buffer was ies/pliva.htm used instead of the recommended phosphate 2. http://apps.who.int/emlib/MedicineDisplay.
buffer in order to make the methodology more aspx?Language=EN&MedIDName=423%40 compatible with LC-MS. The volatile nature azithromycin of ammonia al owing for a good spray in MS 3. Yamauchi K., et al., Azithromycin sup- without suppression of signal and therefore no presses interleukin-12p40 expression in Arithromycin is readily transported to the site loss of sensitivity. An isocratic mix of aque- of infection by the phagocytes where large ous:organic provides a suitable mobile phase stimulated macrophages. Int. J. Biochem. Cell doses can be realised and with a good half- for solubility, retention and selectivity from any Biol. 5, 667-678, (2009) life and a propensity for lipid layers the drug possible degradents.
can remain at the infected tissue site for a sig- nificant length of time. The active substance p/n F18-050905 azithromycin is the subject of a European Pharmacopeia (Ph.Eur.) and USP monograph. Mobile phase Azithromycin is best analysed by HPLC if a high Temp: 20oCpH mobile phase can be utilised. Solubility is Detection: UV 200nm www.fortis-technologies.com Tel: +44 151 336 2266

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