Zibac 500 mg

Description

Indications
Zibac is prescribed for infections caused by susceptible organisms. It is used to treat lower respiratory tract infections such as bronchitis and pneumonia, upper respiratory tract infections including sinusitis and pharyngitis/tonsillitis, as well as otitis media. Additionally, it is effective in treating skin and soft tissue infections. In cases of sexually transmitted diseases, Zibac is indicated for the treatment of non-gonococcal urethritis and cervicitis caused by Chlamydia trachomatis.

Pharmacology
Azithromycin is acid-stable, making it suitable for oral administration without requiring protection from gastric acids. It is readily absorbed, with better absorption on an empty stomach. The peak concentration in adults occurs within 2.1 to 3.2 hours after oral intake. Azithromycin accumulates in phagocytes and is actively transported to infection sites, where it is released in high concentrations during active phagocytosis. Tissue concentrations can exceed plasma levels by more than 50 times due to ion trapping and high lipid solubility.

Azithromycin’s long half-life allows for single-dose administration while maintaining bacteriostatic levels in infected tissues for several days. Following a 500 mg dose, the plasma clearance is approximately 630 mL/min, with a terminal elimination half-life of 68 hours. It is mainly excreted via bile in an unchanged form, while around 6% of the administered dose is excreted unchanged in urine over a week.

Microbiology
Azithromycin functions by binding to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis while leaving nucleic acid synthesis unaffected. It is effective against various bacteria, including:

• Gram-positive bacteria: Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae, Streptococcus pyogenes
• Gram-negative bacteria: Haemophilus ducreyi, Haemophilus influenzae, Moraxella catarrhalis, Neisseria gonorrhoeae
• Other bacteria: Chlamydia pneumoniae, Chlamydia trachomatis, Mycoplasma pneumoniae
• Additional microorganisms: Bordetella pertussis, Legionella pneumophila
• Anaerobic bacteria: Peptostreptococcus species, Prevotella bivia

Dosage and Administration
Oral Administration:

• Adults: 500 mg once daily for 3 days or 500 mg on the first day followed by 250 mg once daily for the next 4 days. For Chlamydia trachomatis-induced sexually transmitted infections, a single 1 g dose is recommended, or alternatively, 500 mg on day 1 followed by 250 mg daily for 2 more days.
• Children: Dosage depends on body weight:
  • 10 mg/kg once daily for 3 days for children over 6 months
  • 15-25 kg: 200 mg (1 teaspoon) daily for 3 days
  • 26-35 kg: 300 mg (1.5 teaspoons) daily for 3 days
  • 36-45 kg: 400 mg (2 teaspoons) daily for 3 days
  • For typhoid fever: 500 mg (2.5 teaspoons) once daily for 7-10 days

Intravenous Infusion (for adults only):

• Community-acquired pneumonia: 500 mg daily via IV for at least 2 days, followed by oral azithromycin (500 mg daily for 7-10 days).
• Pelvic inflammatory disease: 500 mg daily via IV for 1-2 days, followed by oral azithromycin (250 mg daily for 7 days).

Azithromycin for IV infusion is not recommended for children under 16 years.

Administration Instructions
For oral suspension:

1. Shake the bottle well to loosen the powder.
2. Add previously boiled and cooled water up to the water mark.
3. Shake the bottle thoroughly until the powder is fully dissolved.

Azithromycin should be taken at least 1 hour before or 2 hours after meals.

Drug Interactions

• Antacids: Take azithromycin at least 1 hour before or 2 hours after antacids.
• Carbamazepine: No significant interaction observed.
• Cyclosporine: May require dose adjustment; monitor levels closely.
• Digoxin: Risk of increased digoxin levels; monitor accordingly.
• Ergot derivatives: Avoid co-administration due to potential ergotism.
• Methylprednisolone: No significant pharmacokinetic interaction.
• Theophylline: Generally safe, but theophylline levels should be monitored.
• Warfarin: No significant interaction observed, but prothrombin time should be monitored.
• Terfenadine: No notable effects on cardiac repolarization.

Contraindications
Azithromycin is contraindicated in patients with hypersensitivity to azithromycin or other macrolide antibiotics. It should not be taken alongside ergot derivatives or in cases of hepatic disease.

Side Effects
Zibac is generally well tolerated, with most side effects being mild to moderate. Common gastrointestinal effects include nausea, abdominal discomfort, vomiting, flatulence, diarrhea, and loose stools. Allergic reactions such as rash or photosensitivity may occur. Rare cases of hypersensitivity reactions, transient mild reductions in neutrophil counts, cholestatic jaundice, and reversible hearing impairment have been reported in high-dose, prolonged treatments.

Pregnancy and Lactation
Azithromycin falls under Pregnancy Category B, indicating no evidence of fetal harm in animal studies. However, human studies are limited. It should only be used during pregnancy if necessary. It is unclear whether azithromycin passes into breast milk, so caution is advised for nursing mothers.

Precautions and Warnings
Serious allergic reactions, including angioedema and anaphylaxis, have been reported. Some cases required prolonged monitoring and treatment.

• Renal Impairment: No dose adjustment is needed for mild renal impairment (creatinine clearance >40 mL/min), but caution is advised in severe cases.
• Hepatic Impairment: Avoid use in patients with liver disease.
• Driving and Machinery Use: No known effects on alertness or coordination.

Overdose Effects
Symptoms of overdose include hearing loss, severe nausea, vomiting, and diarrhea. Treatment involves gastric lavage and supportive care.

Storage Conditions
Store in a dry place away from heat and light. Keep out of reach of children.

Common Questions

• What is Zibac 500 mg used for?
  It treats bacterial infections such as pneumonia, pharyngitis, and skin infections.
• Is Zibac safe?
  Yes, when used as prescribed by a doctor.
• Can Zibac cause diarrhea?
  Yes, as it affects gut bacteria. If severe, consult a doctor.
• What if symptoms do not improve?
  If no improvement is seen after 3 days, consult a doctor.

Quick Tips

• Complete the full treatment course, even if you feel better.
• Take on an empty stomach for best absorption.
• Avoid antacids 2 hours before or after taking Zibac.
• Stop immediately and seek medical help if allergic reactions occur.