Zithrox 500 Tablet

Indications

Azithromycin is used to treat infections in the lower respiratory tract, such as bronchitis and pneumonia, as well as infections in the upper respiratory tract, such as sinusitis and pharyngitis/tonsillitis, otitis media, and skin and soft tissue infections. Azithromycin is used to treat non-gonococcal infections in both men and women who have sexually transmitted diseases.

Pharmacology

Azithromycin is stable to acid, so it can be taken orally without protecting stomach acid. Easily absorbed; greater absorption on an empty stomach. For oral dosage forms, the time for adults to reach maximum concentration is 2.1 to 3.2 hours. Due to the high concentration in phagocytes, azithromycin is actively transported to the site of infection. During active phagocytosis, high concentrations of azithromycin are released. The concentration of azithromycin in tissues can be 50 times higher than in plasma. This is due to ion trapping and high fat solubility.

 Azithromycin allows a single high-dose administration, but it can still maintain the antibacterial level in the infected tissue for several days. After a single administration of 500 mg, the plasma concentration of azithromycin showed a multiphasic decline, the average apparent plasma clearance rate was 630 ml/min, and the terminal elimination half-life was 68 hours. The extended terminal half-life is believed to be due to the high absorption and subsequent release of the drug from the tissue. The bile excretion of azithromycin (mainly unchanged) is the main route of elimination. Over the course of a week, approximately 6% of the administered dose appeared as the parent drug in the urine.

Microbiology: Azithromycin works by binding to the 50S ribosomal subunit of susceptible microorganisms, thus interfering with microbial protein synthesis. Nucleic acid synthesis is not affected. In vitro and in clinical infections, azithromycin has been shown to be active against most isolates of the following microorganisms:

facultative gram-positive and aerobic microorganisms: Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae, Pyogenic Streptococcus facultative aerobic microorganisms, and  facultative Haemophilic negative microorganisms: , Haemophilus influenzae, Moraxella catarrhalis, Neisseria gonorrhoeae Other microorganisms: Chlamydia pneumoniae, Chlamydia trachomatis, Mycoplasma pneumoniae, β-lactamase production Has no effect on azithromycin activity. Aerobic and gram-positive microorganisms: Streptococcus (group C, F, G), Streptococcus viridans  Aerobic and gram-negative microorganisms: Bordetella pertussis, Legionella pneumophila Anaerobic microorganisms: Distreptococcus, Peptostreptococcus.

Dosage & Administration

Oral-
Adult:

• 500 mg once daily orally for 3 days or 500 mg once on day 1, then 250 mg once on days 2-5 for 4 days.
• For sexually transmitted diseases caused by Chlamydia trachomatis in adults, the dose is 1 gm given as a single dose or 500 mg once on day 1, followed by 250 mg once daily for next 2 days may also be given.

Children:

• 10 mg/kg body weight once daily for 3 days for child over 6 months
• 200 mg (1 teaspoonful) for 3 days if body weight is 15-25 kg
• 300 mg (1½ teaspoonfuls) for 3 days if body weight is 26-35 kg; 400 mg (2 teaspoonfuls) for 3 days if body weight is 36-45 kg.
• In typhoid fever, 500 mg (2½ teaspoonfuls) once daily for 7-10 days is given.

Azithromycin Injection (For IV Infusion only): The recommended dose of Azithromycin for injection for the treatment of adult patients with community-acquired pneumonia due to the indicated organisms is:

• 500 mg as a single daily dose by the intravenous route for at least two days. Intravenous therapy should be followed by Azithromycin by the oral route at a single, daily dose of 500 mg, administered as two 250-mg tablets to complete a 7 to 10-day course of therapy. The timing of the switch to oral therapy should be done at the discretion of the physician and in accordance with clinical response.
• The recommended dose of Azithromycin for the treatment of adult patients with pelvic inflammatory disease due to the indicated organisms is: 500 mg as a single daily dose by the intravenous route for one or two days. Intravenous therapy should be followed by Azithromycin by the oral route at a single, daily dose of 250 mg to complete a 7-day course of therapy. The timing of the switch to oral therapy should be done at the discretion of the physician and in accordance with clinical response. If anaerobic microorganisms are suspected of contributing to the infection, an antimicrobial agent with anaerobic activity should be administered in combination with Azithromycin.
• Safety and effectiveness of azithromycin for injection in children or adolescents under 16 years have not been established.

Interaction

In the presence of food and antacids, the absorption of azithromycin will be reduced. Patients receiving ergot alkaloids should avoid azithromycin because the interaction of azithromycin with the cytochrome P450 system can cause ergot poisoning. Since macrolides increase the plasma concentration of digoxin and cyclosporine, caution should be exercised when combining them. There are no drug interactions between azithromycin and warfarin, theophylline, carbamazepine, methylprednisolone, or cimetidine.

Contraindications

Patients who are hypersensitive to azithromycin or any other macrolide antibiotic should avoid taking it. Ergot derivatives and azithromycin should not be taken together. Patients with hepatic disorders should avoid azithromycin.

Side Effects

Azithromycin is a well-tolerated antibiotic with little adverse effects. Nausea, vomiting, abdominal discomfort (pain/cramps), flatulence, diarrhoea, headache, dizziness, and skin rashes are among the side effects, which are reversible as medication is stopped.

Pregnancy & Lactation

Azithromycin pregnancy category is B. Animal reproduction studies have shown that azithromycin is not harmful to the fetus. There are no adequate and well-controlled studies of pregnant women. Because animal reproduction studies do not always predict human response, azithromycin should be used during pregnancy only when no suitable alternatives are available. Whether azithromycin is secreted in human milk is unclear. Therefore, care should be taken when administering azithromycin to lactating women.

Precautions & Warnings

Azithromycin pregnancy category is B. Animal reproduction studies have shown that azithromycin is not harmful to the fetus. There are no adequate and well-controlled studies of pregnant women. Because animal reproduction studies do not always predict human response, azithromycin should be used during pregnancy only when no suitable alternatives are available. Whether azithromycin is secreted in human milk is unclear. Therefore, care should be taken when administering azithromycin to lactating women.

Therapeutic Class

Therapeutic Class.

Storage Conditions

Keep in a dry place away from light and heat. Keep out of the reach of children.

Pharmaceutical Name

Eskayef Pharmaceuticals Ltd.