Journal Article

Measurement of tissue azithromycin levels in self-collected vaginal swabs post treatment using liquid chromatography and tandem mass spectrometry (LC-MS/MS)

McConville, Malcolm J., Vodstrcil, Lenka A., Bradshaw, Catriona S., Worthington, Karen, Timms, Peter, Tabrizi, Sepehr N., Rupasinghe, Thusitha W. T., Fairley, Christopher K., Huston, Wilhelmina M., Chen, Marcus Y., Kong, Fabian Y. S., Hocking, Jane S., Tull, Dedreia

2017

Overview

Azithromycin is recommended for the treatment of uncomplicated urogenital chlamydia infection although the standard 1gram dose sometimes fails to eradicate the infection (treatment failure). One hypothesis proposed for treatment failure has been insufficient levels of the antibiotic at the site of infection. We developed an assay using liquid chromatography and tandem mass spectrometry (LC-MS/MS) to measure azithromycin concentration in high-vaginal swabs and monitor how concentration changes over time following routine azithromycin treatment. Azithromycin concentrations were measured in two groups of women either within the first 24h of taking a 1g dose (N = 11) or over 9 days (N = 10). Azithromycin concentrations were normalised to an internal standard (leucine enkephalin), and the bulk lipid species phosphatidylcholine [PC(34:1)], using an Agilent 6490 triple quadrupole instrument in positive ionisation mode. The abundances of azithromycin, PC(34:1), and leu-enkephalin were determined by multiple reaction monitoring and absolute levels of azithromycin estimated using standard curves prepared on vaginal specimens. Vaginal azithromycin concentrations of women were rapidly obtained after 5h post-treatment (mean concentration = 1031mcg/mg of lipid, range = 173-2693mcg/mg). In women followed for 9 days, peak concentrations were highest after day 2 (mean concentration = 2206mcg/mg, range = 721-5791mcg/mg), and remained high for at least 9 days with a mean concentration of 384mcg/mg (range = 139-1024mcg/mg) on day 9. Our study confirmed that a single 1g dose of azithromycin is rapidly absorbed and remains in the vagina at relatively high levels for at least a week, suggesting that poor antibiotic absorption is unlikely to be an explanation for treatment failure.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Anti-Bacterial Agents - blood / Anti-Bacterial Agents - metabolism / Anti-Bacterial Agents - pharmacokinetics / Antibiotics / Antimicrobial agents / Azithromycin / Azithromycin - blood / Azithromycin - metabolism / Azithromycin - pharmacokinetics / Biology and Life Sciences / Care and treatment / Chemotherapy / Chlamydia / Chlamydia infections / Chromatography / Chromatography, Liquid - methods / Condoms / Development and progression / Diagnosis / Dosage and administration / Drug dosages / Drug resistance / Enkephalin (leucine) / Enkephalin, Leucine - blood / Enkephalin, Leucine - metabolism / Enkephalin, Leucine - pharmacokinetics / Enkephalins / Epidemiology / Failure / Female / Health aspects / Humans / Infections / Infectious diseases / Lecithin / Leucine / Lipids / Liquid chromatography / Mass spectrometry / Mass spectroscopy / Measurement / Medicine and Health Sciences / Mutation / Phosphatidylcholine / Population / Quadrupoles / Research and Analysis Methods / Risk factors / Scientific imaging / Sexually transmitted diseases / Spectroscopy / STD / Tandem Mass Spectrometry - methods / Vagina / Vagina - metabolism / Vaginal diseases / Womens health