azithromycin

see also:

• macrolide antibiotics

• 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

• 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.

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

• 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
• antibiotic associated pseudomembranous colitis

• 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

• 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)

• community acquired pneumonia
• pertussis
• Legionella
• bronchiectasis, COPD - 3 doses per week reduces exacerbation rates but may increase macrolide-resistance especially in children, some may develop irreversible hearing loss
• sexually transmitted infections (STDs/STIs) such as epididymo-orchitis, pelvic inflammatory disease (PID), chancroid, granuloma inguinale
• bacterial enteritis such as Camplylobacter, Salmonella, cholera, traveller's diarrhoea, Salmonella typhi (typhoid enteric fever), paratyphoid enteric fever
• severe Cat scratch disease
• Australian tick typhus or scrub typhus
• as an immunomodulator (although new non-antibiotic agents will avoid antibiotic risks):
  • lung transplants resulting in bronchiolitis obliterans syndrome
  • cystic fibrosis
  • sepsis - to reduce cytokine storm
  • severe respiratory viral infections

• 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.

• 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

• sexually transmitted infections (STDs/STIs):
  • 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;