Azithromycin
For additional information see Macrolides
For drug interactions see Macrolides, Azithromycin
HIDE CLASS
Mode of action
Mode of action from Macrolides
Bacteriostatic; inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit. They also have immunomodulatory and anti-inflammatory effects.
Indications
Chlamydial infections, eg cervicitis, trachoma
Streptococcal pharyngitis/tonsillitis
Community-acquired pneumonia
Prevention and treatment of Mycobacterium avium complex (MAC) infection, with other agents
Donovanosis (granuloma inguinale)
Typhoid, paratyphoid (enteric fever)
Traveller’s diarrhoea
Prevention and treatment of pertussis
Indications from Macrolides
Treatment and prevention of infections due to susceptible bacteria (including use in penicillin or cephalosporin allergy)
Precautions
Risk factors for prolonged QT interval—azithromycin has been associated with prolonged QT interval.
Diabetes—oral liquid contains sucrose 3.87 g/5 mL.
Hepatic
Use with caution in severe impairment; consider dose reduction.
Children
Limited information about use in children <6 months, especially in neonates, however, it has been associated with infantile hypertrophic pyloric stenosis (below).
Precautions from Macrolides
Serious allergy to macrolides—contraindicated.
Myasthenia gravis—macrolides may aggravate condition.
Pregnancy
Considered safe to use if it is the treatment of choice.
Breastfeeding
Safe to use; may cause loose bowel actions in infant.
Adverse effects
Common (>1%)
inflammation and pain at infusion site
Rare (<0.1%)
torsades de pointes (very rare), infantile hypertrophic pyloric stenosis (below), multi-organ hypersensitivity syndrome
Infantile hypertrophic pyloric stenosis
Has been associated with use of azithromycin, particularly during the first 2 weeks of life; after this, the risk decreases, with no increased risk after 7 weeks of age. Risk is less than with erythromycin.
Adverse effects from Macrolides
Common (>1%)
nausea, vomiting, diarrhoea, abdominal pain and cramps, candidal infections
Infrequent (0.1–1%)
rash, headache
Rare (<0.1%)
hypersensitivity (eg anaphylaxis, fixed drug eruptions, Stevens-Johnson syndrome, interstitial nephritis), psychiatric disturbances, ototoxicity (eg tinnitus, dizziness, hearing loss), Clostridioides difficile-associated disease, cholestatic hepatitis, pancreatitis, prolonged QT interval, blood dyscrasias, eg thrombocytopenia
Dosage – Azithromycin
Adult
Oral, 500 mg once on day 1. Then give 500 mg once daily for 2 days or 250 mg once daily for 4 days. The higher dose can be given for >3 days, depending on the infection.
Child
>6 months, oral 10 mg/kg (maximum 500 mg) once on day 1. Then give 10 mg/kg (maximum 500 mg) once daily for 2 days or 5 mg/kg (maximum 250 mg) once daily for 4 days. The higher dose can be given for >3 days, depending on the infection.
Chlamydial infection, gonococcal genital infection
Adult, oral 1 g as a single dose. Seek specialist advice if treating an infection due to Mycoplasma genitalium as it may be resistant to azithromycin.
Trachoma and Chlamydia trachomatis conjunctivitis
Adult, child, oral 20 mg/kg (maximum 1 g) as a single dose.
Community-acquired pneumonia
Adult, IV 500 mg once daily; change to oral route when possible.
MAC
Treatment
HIV-negative adult, oral 250 mg once daily.
HIV-positive adult, oral 500–600 mg once daily.
HIV-positive child, oral 10 mg/kg (maximum 500 mg) once daily.
Prevention
Primary prevention, adult, oral 1.2 g taken once a week.
Primary prevention, child, oral 20 mg/kg (maximum 1.2 g) once a week or 5 mg/kg (maximum 250 mg) once daily.
Secondary prevention, adult, oral 500–600 mg once daily.
Secondary prevention, child, oral 5 mg/kg (maximum 250 mg) once daily.
Donovanosis (granuloma inguinale)
Adult, oral 500 mg once daily for 7 days; or 1 g as a single dose once a week for 4 weeks or until healed.
Typhoid, paratyphoid
Adult, child >1 year, oral 20 mg/kg (maximum 1 g) once daily for 5–7 days.
Traveller’s diarrhoea
Adult, oral 1 g single dose or 500 mg once daily for 3 days.
Child, oral 10 mg/kg (maximum 500 mg) once daily for 3 days has been suggested but evidence is lacking.
Pertussis prevention and treatment
Adult, oral 500 mg on day 1, then 250 mg once daily for 4 days.
Child >6 months, oral 10 mg/kg (maximum 500 mg) on day 1, then 5 mg/kg (maximum 250 mg) once daily for 4 days.
Child <6 months, oral 10 mg/kg once daily for 5 days.
Maximum
Oral, 1.2 g as a single dose (in MAC).
Administration advice
Give a 500 mg dose IV over at least 1 hour; ideally infuse a concentration of 1 mg/mL over 3 hours and one of 2 mg/mL over 1 hour.
Counselling
Parents of neonates: tell your doctor if your baby develops vomiting or is irritable when feeding while taking azithromycin.
Practice points
high level azithromycin resistance in S. pneumoniae can occur after a single dose of azithromycin
Practice points from Macrolides
there is often cross-resistance between macrolides and lincosamides (clindamycin and lincomycin)
the immunomodulatory and anti-inflammatory effects of macrolides are used in:
diffuse panbronchiolitis, where improved lung function has greatly increased survival
cystic fibrosis, where azithromycin may help improve or maintain lung function and decrease the number of antibacterial courses (however, with long-term treatment, pulmonary function may again deteriorate and macrolide resistance in S. aureus occurs)
although inactive against P. aeruginosa, macrolides reduce biofilm production in mucoid strains and also inhibit some virulence factors; this may contribute to their effects in cystic fibrosis and diffuse panbronchiolitis
Products
Search for Azithromycin on the PBS
tab, 500 mg, 2, 3, Zithromaxa, PBS‑R[2]1,2/RPBS‑R[3]3
tab, 500 mg (scored), 2, 3, Zithroa, PBS‑R[2]1,2/RPBS‑R[3]3
tab, 600 mg (scored), 8, Zithromax, PBS‑S100[16]4
oral liquid, 40 mg/mL (powder), 15 mL, Zithromax, PBS‑R2
inj, 500 mg (powder), 1, Azith, Zithromaxa
inj, 500 mg (powder), 5, Azithromycin
1 uncomplicated urethritis or cervicitis due to C. trachomatis
2 trachoma
3 upper and lower respiratory tract infections
4 prevention of MAC infections in HIV infection, see PBS
a generic brands available