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azithromycin

azithromycin

introduction

  • azithromycin is a broad spectrum antibiotic which acts by inhibition of protein synthesis in bacteria by binding to the 50S ribosomal subunit and preventing translocation of peptides.
  • it is the first of a class of antibiotics designated chemically as azalides, a subclass of macrolide antibiotics
  • category B1 in pregnancy
  • should only be used in breastfeeding women where adequate alternatives are not available as no data available on excretion into milk.
  • safety not verified in children

antibiotic spectrum

  • Gram positive aerobic bacteria including St. aureus, Streptococcus pyogenes, Strep. pneumoniae
    • cross resistance with erythromycin resistant Gram positive strains
    • In Australia, macrolide resistance for Strep. pneumoniae and Staph. aureus has been increasing since the late 1990s. Resistance rates of 15% or more are regularly reported.
  • Gram negative aerobic bacteria including H. influenzae, Legionella, B. pertussis, Shigella, V. cholerae
    • variable activity against E.coli, Salmonella, Enterobacter, Klebsiella
    • Proteus, Serratia, Morganella and Pseudomonas are usually resistant
  • Anaerobic bacteria including Bacteroides, Clostridium perfringens, Propionibacterium acnes
  • sexually transmitted infections (STDs/STIs) organisms including Chlamydia, syphilis, gonococcus
  • other bacteria including Borrelia, Mycoplasma, Ureaplasma, Campylobacter, Listeria and Mycobacterium avium-intracellulare complex.

contraindications

  • Known hypersensitivity to azithromycin, erythromycin or any macrolide or ketolide antibiotic

adverse effects

  • allergic reactions including anaphylaxis but these are rare
  • diarrhoea, nausea, abdominal pain occur uncommonly
  • candidiasis
  • interstitial nephritis
  • prolonged QTc (rare) thus avoid with drugs that also prolong QTc
  • hepatitis and cholestatic jaundice which in rare cases may be fatal
  • deafness and tinnitus have been reported

drug interactions of note

  • may increase toxicity of colchicine via increased concentrations
  • may increase risk of rhabdomyolysis in patients on statins
  • in patients receiving ergot derivatives, ergotism has been precipitated by coadministration of some macrolide antibiotics
  • care with concurrent administration with cyclosporin as cyclosporin serum levels increase
  • macrolide antibiotics may alter gut flora and cause increased serum levels of digoxin in patients on digoxin.
  • avoid concomitant antacid administration with oral doses as reduces peak concentration of azithromycin

indications

Australian PBS approved indications

  • trachoma
  • uncomplicated urethritis or cervicitis due to Chlamydia trachomatis
  • prevention of Mycobacterium avium complex in patients with HIV / AIDS and low CD4 counts
  • respiratory tract infections (Repat schedule only)

other indications

dosage

  • no dose adjustment is needed in patient's with mild or moderate renal impairment (GFR 10-80 mL/min).
  • no dose adjustment is recommended for patients with mild to moderate hepatic impairment but care sghould be taken in those with liver impairment.

iv infusion dose

  • do not administer as an iv bolus or as an intramuscular injection
  • administer iv dose as an intravenous infusion over not less than 60 minutes
  • infusion should be either 1 mg/mL over three hours or 2 mg/mL over one hour1)
  • usual adult dose 500mg daily for 2 days then change to oral

adult oral dose

    • 1g oral as single dose or weekly for up to 3 weeks
  • pneumonia following initial 2 days of iv Rx:
    • 500mg o daily for 7-10days
  • prevention of disseminated Mycobacterium avium complex disease:
    • 1.2 g once wkly (+/- rifabutin)
  • other indications:
    • 500 mg on day 1, 250 mg daily on days 2-5; alternative regimen: 500 mg daily for 3 days;
1)
MIMS Zithromax PI 2011
azithromycin.txt · Last modified: 2015/06/06 17:58 (external edit)