Zithrin 500 mg

Description

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

Pharmacology Azithromycin, the active ingredient in Zithrin, is stable in acidic environments and can be taken orally without the need for gastric protection. It is efficiently absorbed, with better absorption occurring on an empty stomach. The peak plasma concentration is achieved within 2.1 to 3.2 hours following oral administration. Due to its high concentration in phagocytes, azithromycin is actively transported to infection sites and is released in significant amounts during phagocytosis. Tissue concentrations can exceed plasma levels by over 50 times due to ion trapping and its lipid solubility.

Azithromycin has an extended half-life, allowing for a single large dose to maintain bacteriostatic levels in infected tissues for several days. After a 500 mg dose, plasma levels decrease in a polyphasic manner, with an average plasma clearance rate of 630 mL/min and a terminal elimination half-life of 68 hours. The primary route of elimination is biliary excretion, with approximately 6% of the administered dose excreted unchanged in urine over a week.

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

• Aerobic and facultative gram-positive bacteria: Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae, Streptococcus pyogenes.
• Aerobic and facultative gram-negative bacteria: Haemophilus ducreyi, Haemophilus influenzae, Moraxella catarrhalis, Neisseria gonorrhoeae.
• Other bacteria: Chlamydia pneumoniae, Chlamydia trachomatis, Mycoplasma pneumoniae.
• Additional aerobic and facultative gram-positive bacteria: Streptococci (Groups C, F, G), Viridans group streptococci.
• Aerobic and facultative gram-negative bacteria: Bordetella pertussis, Legionella pneumophila.
• Anaerobic bacteria: Peptostreptococcus species, Prevotella bivia.

Dosage and Administration

Oral Dosage:

• Adults: 500 mg once daily for 3 days, or 500 mg on the first day followed by 250 mg daily for the next 4 days.
• Sexually transmitted infections caused by Chlamydia trachomatis: 1 g as a single dose or 500 mg on the first day, followed by 250 mg daily for the next 2 days.
• Children (over 6 months):
  • 10 mg/kg body weight once daily for 3 days.
  • 200 mg daily for 3 days for body weight 15-25 kg.
  • 300 mg daily for 3 days for body weight 26-35 kg.
  • 400 mg daily for 3 days for body weight 36-45 kg.
  • Typhoid fever: 500 mg daily for 7-10 days.

Intravenous Infusion (IV Only):

• Community-acquired pneumonia: 500 mg IV once daily for at least two days, followed by 500 mg orally daily to complete a 7 to 10-day course.
• Pelvic inflammatory disease: 500 mg IV once daily for 1-2 days, followed by 250 mg orally daily to complete a 7-day course.

Reconstitution Procedure for Suspension:

1. Shake the bottle to loosen the powder.
2. Add boiled and cooled water up to the marked level.
3. Shake well until fully mixed.
4. Administer at least 1 hour before or 2 hours after meals.

Drug Interactions

• Antacids: Azithromycin should be taken at least 1 hour before or 2 hours after antacids.
• Carbamazepine: No significant effect on plasma levels was observed.
• Cyclosporine: Caution is advised as some macrolides interfere with cyclosporine metabolism. Monitoring is recommended if co-administered.
• Digoxin: Possible impaired metabolism leading to increased digoxin levels; monitoring is required.
• Ergot Derivatives: Risk of ergotism; co-administration should be avoided.
• Methylprednisolone: No significant interaction observed.
• Theophylline: No significant interaction, but monitoring is advised.
• Warfarin: No alteration in anticoagulant effects, but prothrombin time should be monitored.
• Terfenadine: No significant effect on pharmacokinetics or cardiac repolarization.

Contraindications Azithromycin is contraindicated in individuals with known hypersensitivity to azithromycin or other macrolide antibiotics. Co-administration with ergot derivatives is not recommended. Patients with hepatic disease should avoid its use.

Side Effects Common side effects include gastrointestinal discomfort such as nausea, abdominal pain, vomiting, flatulence, diarrhea, and loose stools. Allergic reactions like rash or photosensitivity may occur. Rare cases of serious hypersensitivity reactions, reversible liver enzyme elevations, and transient mild neutrophil reductions have been reported. Hearing impairment has been observed in some patients receiving prolonged high doses.

Use in Pregnancy & Lactation Azithromycin falls under Pregnancy Category B. Animal studies have shown no harm to the fetus, but adequate human studies are lacking. It should be used during pregnancy only if no safer alternatives are available. It is unknown if azithromycin is excreted in breast milk, so caution is advised for nursing mothers.

Precautions & Warnings Serious allergic reactions, including angioneurotic edema and anaphylaxis, have been reported. Some cases required prolonged observation and treatment. Caution is advised in patients with renal impairment (creatinine clearance <40 ml/min) and hepatic impairment due to the liver being the main route of excretion. No significant effect on driving or operating machinery has been observed.

Overdose Effects Overdose symptoms may include hearing loss, severe nausea, vomiting, and diarrhea. Treatment involves gastric lavage and supportive care.

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

Frequently Asked Questions

• Can Zithrin cause diarrhea? Yes, it may affect gut bacteria balance, leading to diarrhea. Severe cases should be reported to a doctor.
• Is Zithrin an antibiotic? Yes, it is a macrolide antibiotic used to treat bacterial infections.
• What should I do if symptoms persist after taking Zithrin? If symptoms do not improve within three days, consult a doctor.
• Can I take Zithrin with antacids? Avoid taking antacids within two hours before or after Zithrin.

Quick Tips

• Complete the full prescribed course even if symptoms improve early.
• Take Zithrin at least 1 hour before or 2 hours after food.
• Inform your doctor if severe diarrhea or allergic reactions occur.