What is a Z pack (azithromycin) used for?

What is a Z-Pack (Azithromycin) Used For?

Azithromycin (Z-Pack) is FDA-approved for treating respiratory tract infections (community-acquired pneumonia, acute bacterial sinusitis, COPD exacerbations), pharyngitis/tonsillitis, uncomplicated skin infections, and sexually transmitted infections (chlamydia, gonorrhea, chancroid), though it should NOT be first-line for most of these conditions due to rising resistance and safety concerns. 1

FDA-Approved Indications

Respiratory Tract Infections

• Community-acquired pneumonia caused by Chlamydophila pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, or Streptococcus pneumoniae in patients appropriate for oral therapy 1
• Acute bacterial sinusitis due to H. influenzae, Moraxella catarrhalis, or S. pneumoniae 1
• Acute bacterial exacerbations of COPD due to H. influenzae, M. catarrhalis, or S. pneumoniae 1
• Pharyngitis/tonsillitis caused by Streptococcus pyogenes as an alternative when first-line therapy cannot be used 1

Skin and Soft Tissue Infections

• Uncomplicated skin and skin structure infections due to Staphylococcus aureus, Streptococcus pyogenes, or Streptococcus agalactiae (abscesses require surgical drainage) 1

Sexually Transmitted Infections

• Urethritis and cervicitis due to Chlamydia trachomatis or Neisseria gonorrhoeae 1
• Genital ulcer disease (chancroid) in men due to Haemophilus ducreyi 1

Critical Prescribing Limitations

When NOT to Use Azithromycin as First-Line

For Community-Acquired Pneumonia:

• Do NOT use in moderate-to-severe illness, hospitalized patients, cystic fibrosis, nosocomial infections, suspected bacteremia, elderly/debilitated patients, or those with immunodeficiency/functional asplenia 1
• Beta-lactams remain first-line for hospitalized CAP patients 2
• Avoid monotherapy in regions with >25% macrolide-resistant S. pneumoniae 3

For Sexually Transmitted Infections:

• Doxycycline is preferred for chlamydial and non-gonococcal urethritis; use azithromycin ONLY if doxycycline fails, is contraindicated, or adherence is a major concern 4, 2, 3
• Azithromycin efficacy for Mycoplasma genitalium has declined dramatically from 85.3% (before 2009) to 67.0% (since 2009) 4, 3

For Pharyngitis/Tonsillitis:

• Penicillin remains the drug of choice for S. pyogenes infection and rheumatic fever prophylaxis 1
• Azithromycin results in more recurrence than penicillin, necessitating higher dosing (12 mg/kg/day for 5 days in children) 5

Specialized Long-Term Uses

Cystic Fibrosis

• Chronic azithromycin (500mg three times weekly or 250mg daily) is recommended for patients ≥6 years with persistent Pseudomonas aeruginosa in airway cultures 2, 3
• Improves lung function (FEV1 increase of 3.6-6.2%) and reduces exacerbations 3, 6
• Also beneficial in CF patients WITHOUT P. aeruginosa for reducing exacerbations 2

COPD

• Long-term azithromycin reduces exacerbations in moderate-to-severe COPD (rate reduction from 1.83 to 1.48 per patient-year, RR 0.83) 6

Critical Safety Warnings

Cardiac Risks

• Can cause fatal cardiac arrhythmias including torsades de pointes 2, 3
• Avoid or use with extreme caution in patients with known QT prolongation or history of torsades de pointes 2, 3
• Risk of fatal arrhythmias is 1.1 cases per 1000 person-years 6

Contraindications

• Hypersensitivity to azithromycin, erythromycin, any macrolide, or ketolide 3
• Current non-tuberculous mycobacteria (NTM) infection is an absolute contraindication for long-term therapy 3
• Screen for TB in high-risk populations before initiating empiric azithromycin for pneumonia to avoid delayed tuberculosis diagnosis 2, 3

Resistance Concerns

• High macrolide resistance creates a prolonged "window" of subinhibitory drug concentrations lasting 14-20 days, promoting resistance development 2
• Consider local resistance patterns before prescribing 2

Dosing Considerations

• Standard adult dosing: 500mg on day 1, then 250mg daily for days 2-5 (total 7-10 days for CAP) 2, 7, 8
• Single-dose regimen: 1g single dose for certain STIs 7, 8
• Pediatric dosing: 10mg/kg/day for 3 days OR 10mg/kg day 1, then 5mg/kg/day for 4 days 5

Drug Interactions and Precautions

• Monitor prothrombin time carefully when co-administered with oral anticoagulants 1
• Do NOT take simultaneously with aluminum- and magnesium-containing antacids 1
• Avoid concurrent use with terfenadine, astemizole, pimozide, or cisapride due to fatal arrhythmia risk 3
• Exercise caution in impaired hepatic function and severe renal insufficiency (GFR <10 mL/min) 1
• Can exacerbate myasthenia gravis symptoms 1

Common Adverse Effects

• Gastrointestinal effects (nausea, diarrhea, abdominal pain, dispepsia, colitis) occur in <5% of patients 6, 7
• Better GI tolerance than erythromycin 7, 8
• Long-term use may cause hearing loss and colonization with resistant organisms 6