What is the prescription and usage for Z pack (azithromycin)?

Z-Pack (Azithromycin): Prescription and Clinical Uses

Azithromycin (Z-Pack) is prescribed as 500 mg on day 1, followed by 250 mg daily on days 2-5 for adults, and is FDA-approved for treating community-acquired pneumonia, acute bacterial sinusitis, acute exacerbations of chronic bronchitis, pharyngitis/tonsillitis, uncomplicated skin infections, and certain sexually transmitted infections including chlamydia and gonorrhea. 1

Standard Dosing Regimens

Adults

• Respiratory infections: 500 mg on day 1, then 250 mg daily for days 2-5 (total 5-day course) 2, 1
• Chlamydia/gonorrhea: Single 1-gram dose 2, 3
• Community-acquired pneumonia: 500 mg on day 1, then 250 mg daily for days 2-5 2, 1

Pediatric Dosing

• Infants <6 months: 10 mg/kg daily for 5 days 2
• Children ≥6 months: 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg daily (max 250 mg) on days 2-5 2
• Alternative pediatric regimen: 12 mg/kg daily for 5 days for streptococcal pharyngitis 4

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 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 infections due to Staphylococcus aureus, Streptococcus pyogenes, or Streptococcus agalactiae 1

Sexually Transmitted Infections

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

Critical Contraindications and Warnings

Absolute Contraindications

• Hypersensitivity to azithromycin, erythromycin, any macrolide, or ketolide 2, 5
• History of cholestatic jaundice or hepatic dysfunction with prior azithromycin use 2
• Active non-tuberculous mycobacterial infection (for long-term therapy) 5

Cardiovascular Risks

• QT prolongation warning: Azithromycin can cause ventricular tachycardia and torsades de pointes; avoid or use with extreme caution in patients with known QT prolongation 2, 5
• Do not combine with terfenadine, astemizole, pimozide, or cisapride due to fatal arrhythmia risk 2, 5

Important Clinical Limitations

• Not appropriate for pneumonia in patients with moderate-to-severe illness, cystic fibrosis, nosocomial infections, bacteremia, hospitalized patients, elderly/debilitated patients, or immunodeficiency 1
• Avoid monotherapy in regions with >25% macrolide-resistant S. pneumoniae 5
• Cannot treat syphilis: All patients with STIs should have syphilis testing, as azithromycin may mask incubating syphilis 1

Special Populations

Pregnancy

• FDA Category B: Azithromycin is the preferred macrolide during pregnancy, safer than clarithromycin 5
• Appropriate for treating chlamydia and other bacterial infections in pregnant women 2, 5

Pediatric Considerations

• Infants <1 month: Azithromycin is preferred over erythromycin for pertussis due to lower risk of infantile hypertrophic pyloric stenosis (IHPS) 2
• Monitor infants receiving macrolides for IHPS and other serious adverse events 2

HIV-Infected Patients

• Azithromycin is appropriate for bacterial respiratory infections in HIV-infected patients 5
• Same dosing regimens as HIV-negative patients 2

Resistance and Screening Considerations

Tuberculosis Screening

• Screen high-risk populations for TB before initiating empiric azithromycin for pneumonia to avoid delayed tuberculosis diagnosis 5

Macrolide Resistance

• Erythromycin-resistant organisms are also resistant to azithromycin 6
• For streptococcal pharyngitis, susceptibility testing should be performed as some strains are resistant 1
• Azithromycin efficacy for Mycoplasma genitalium has declined from 85.3% (pre-2009) to 67.0% (post-2009) 5

Common Adverse Effects

Gastrointestinal (Most Common)

• Nausea, vomiting, diarrhea, abdominal pain, and anorexia 2
• Better gastrointestinal tolerance than erythromycin 7, 8

Serious Adverse Events

• Pseudomembranous colitis, hepatitis, pancreatitis 2
• Stevens-Johnson syndrome, toxic epidermal necrolysis 2
• Reversible hearing loss, acute renal failure 2

Drug Interactions

Avoid Concurrent Use

• Aluminum- or magnesium-containing antacids (reduce absorption; separate dosing) 2
• Drugs metabolized by cytochrome P450 system require monitoring 2

Use Caution With

• Digoxin, triazolam, ergot alkaloids 2
• Oral anticoagulants, azole antifungals, benzodiazepines, calcium-channel blockers, carbamazepine 2, 5

Key Clinical Pearls

• Single-dose advantage: For chlamydia, the 1-gram single dose offers superior compliance compared to multi-day regimens 6, 3
• Tissue penetration: Low serum concentrations are offset by extensive tissue distribution and intracellular accumulation 6, 7
• Long half-life: Terminal elimination half-life up to 5 days allows once-daily dosing 7, 8
• Food interaction: Taking with a large meal may reduce absorption by up to 50% 7