Zetron (Azithromycin)

Uses

Zetron (Azithromycin) is used for infections caused by susceptible organisms in-

Upper respiratory tract infections including sinusitis, pharyngitis and tonsillitis

Lower respiratory tract infections including bronchitis, acute bacterial exacerbations of chronic obstructive pulmonary

disease (COPD)

Otitis media

Skin and soft tissue infections including cellulitis, pyoderma, erysipelas, wound infections

Diarrhea, Shigellosis

Sexually transmitted diseases, especially in the treatment of non-gonococcal urethritis and cervicitis due to Chlamydia trachomatis

Genital ulcer disease in men due to Haemophilus ducreyi (chancroid)

Mild or moderate typhoid due to multiple-antibacterial resistant organisms

Prophylaxis against a-hemolytic (viridans group) streptococcal bacterial endocarditis

Other infections including odontogenic infections, bartonella infections, toxoplasmosis, babesiosis

Zetron (Azithromycin) is also used to associated treatment for these conditions: Acute Bacterial Sinusitis (ABS), Acute Otitis Media, Acute bacterial exacerbation of COPD caused by Haemophilus Influenza Infections, Moraxella Catarrhalis Infection, Streptococcus Pneumoniae Infections, Bacterial Conjunctivitis, Bacterial Sinusitis, Cervicitis, Chancroid, Community Acquired Pneumonia (CAP), Genital Ulcer Disease (GUD), Pelvic Inflammatory Disease (PID), Pharyngitis, Streptococcal Pharyngitis, Streptococcal tonsillitis, Tonsillitis bacterial, Traveler's Diarrhea, Uncomplicated Skin and Skin Structure Infections, Urethritis

How Zetron (Azithromycin) works

In order to replicate, bacteria require a specific process of protein synthesis, enabled by ribosomal proteins . Zetron (Azithromycin) binds to the 23S rRNA of the bacterial 50S ribosomal subunit. It stops bacterial protein synthesis by inhibiting the transpeptidation/translocation step of protein synthesis and by inhibiting the assembly of the 50S ribosomal subunit , . This results in the control of various bacterial infections , . The strong affinity of macrolides, including azithromycin, for bacterial ribosomes, is consistent with their broad‐spectrum antibacterial activities .

Zetron (Azithromycin) is highly stable at a low pH, giving it a longer serum half-life and increasing its concentrations in tissues compared to erythromycin .

Dosage

Zetron (Azithromycin) dosage

Zetron (Azithromycin) tablet can be taken with or without food. Zetron (Azithromycin) suspension should be taken at least 1 hour before or 2 hours after meal.

Oral:

Adult:

For respiratory tract infections, otitis media and skin & soft tissue infections: 500 mg once daily for 3 days or an alternative to this as 500 mg once on day 1, followed by 250 mg once daily for next 4 days. For sexually transmitted diseases like genital ulcer, non-gonococcal urethritis and cervicitis due to Chlamydia trachomatis : a single 1 gm (1000 mg) dose. For the treatment of urethritis and cervicitis due to Neisseria gonorrhoeae : a single 2 gm (2000 mg) dose. In typhoid, 500 mg once daily for 7 days. In Cholera, a single 1 gm (1000 mg) dose. In Shigellosis, 500 mg once on day 1, followed by 250 mg once daily for next 4 days.

Zetron (Azithromycin) can be taken with or without food.

To reconstitute Zetron (Azithromycin) 15 ml powder for suspension: Add 10 ml or 2 tea spoonfuls of just boiled and cooled water to the content of the bottle and shake well to mix uniformly.

To reconstitute Zetron (Azithromycin) 30 ml powder for suspension: Add 20 ml or 4 tea spoonfuls of just boiled and cooled water to the content of the bottle and shake well to mix uniformly.

To reconstitute Zetron (Azithromycin) 50 ml powder for suspension: Add 35 ml or 7 tea spoonfuls of just boiled and cooled water to the content of the bottle and shake well to mix uniformly.

Side Effects

Zetron (Azithromycin) is well tolerated with a low incidence of side efects. The side effects include nausea, vomiting, abdominal discomfort (pain/cramps), flatulence, diarrhea, headache, dizziness, and skin rashes and are reversible upon discontinuation of therapy. Reversible elevations in liver transaminases have been observed occasionally. Transient mild reductions in neutrophil counts have occasionally been observed in clinical trials, although causal relationship to Zetron (Azithromycin) has not been established.

Toxicity

Rat Oral LD50: >2000 mk/kg

Possible major adverse effects include cardiovascular arrhythmias and hearing loss. Macrolide resistance is also an ongoing issue. Hepatotoxicity has been observed in rare cases.

A note on the risk of liver toxicity:

Due to the act that azithromycin is mainly eliminated by the liver, caution should be observed when azithromycin is given to patients with decreased hepatic function .

A note on potential renal toxicity:

Because limited data in patients with renal GFR Label.

Use in Pregnancy:

This drug is categorized as a pregnancy category B drug. Reproduction studies have been done in rats and mice at doses up to moderately maternally toxic doses (for example, 200 mg/kg/day). These doses, based on a mg/m2 basis, are approximately 4 and 2 times, respectively, the human daily dose of 500 mg. In the animal studies, no harmful effects to the fetus due to azithromycin were observed. There are, at this time, no conclusive and well-controlled studies that have been done in pregnant women. Because animal reproduction studies do not always predict human response, azithromycin should be used during pregnancy only if clearly needed .

Nursing Mothers:

It is unknown at this time whether azithromycin is excreted in human milk. Because many other drugs are excreted in human milk, caution should be observed when azithromycin is given to a nursing woman .

Carcinogenesis, Mutagenesis, Impairment of Fertility:

Long-term studies in animals have not been performed to study carcinogenic potential. Zetron (Azithromycin) has demonstrated no potential to be mutagenic in standard laboratory tests. No evidence of negative effects on fertility due to azithromycin was found .

Precaution

As with any antibiotic, observation for signs of super infection with non-susceptable organisms, including fungi, is recommended. Precaution should be taken in patients with more severe renal impairment.

Interaction

Antacids: Peak serum levels but not the total extent of absorption are reduced by aluminium and magnesium containing antacids in the stomach. Zetron (Azithromycin) should therefore be taken at least 1 hour before or 2 hours after taking these antacids.

Ergot Derivatives: Because of the theoretical possibility of ergotism, concomitant administration of ergot derivatives and Zetron (Azithromycin) should be avoided. Digoxin & Cyclosporin: Macrolides have been known to increase the plasma concentration of Digoxin & Cyclosporin and so caution should be exercised while co-administration is necessary.

Anti-Histamines: A potentially life threatening interaction between erythromycin and terfenadine or astemizole have been reported. Although such an interaction with Zetron (Azithromycin) is not established yet, it is wise to avoid concomitant use of Zetron (Azithromycin) and terfenadine or astemizole.

Food Interaction

• Take on an empty stomach. Take at least 1 hour before or 2 hours after meals.

Zetron (Azithromycin) Drug Interaction

Moderate: albuterol, albuterolUnknown: diphenhydramine, diphenhydramine, fluticasone nasal, fluticasone nasal, guaifenesin, guaifenesin, montelukast, montelukast, acetaminophen, acetaminophen, cyanocobalamin, cyanocobalamin, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol, cetirizine, cetirizine

Zetron (Azithromycin) Disease Interaction

Major: colitis, QT prolongationModerate: liver disease, myasthenia gravis

Volume of Distribution

After oral administration, azithromycin is widely distributed in tissues with an apparent steady-state volume of distribution of 31.1 L/kg . Significantly greater azithromycin concentrations have been measured in the tissues rather than in plasma or serum , . The lung, tonsils and prostate are organs have shown a particularly high rate of azithromycin uptake .

This drug is concentrated within macrophages and polymorphonucleocytes, allowing for effective activity against Chlamydia trachomatis . In addition, azithromycin is found to be concentrated in phagocytes and fibroblasts, shown by in vitro incubation techniques. In vivo studies demonstrate that concentration in phagocytes may contribute to azithromycin distribution to inflamed tissues .

Elimination Route

Bioavailability of azithromycin is 37% following oral administration. Absorption is not affected by food. Macrolide absorption in the intestines is believed to be mediated by P-glycoprotein (ABCB1) efflux transporters, which are known to be encoded by the ABCB1 gene .

Half Life

Terminal elimination half-life: 68 hours

Clearance

Mean apparent plasma cl=630 mL/min (following single 500 mg oral and i.v. dose)

Elimination Route

Biliary excretion of azithromycin, primarily as unchanged drug, is a major route of elimination. Over a 1 week period, approximately 6% of the administered dose is found as unchanged drug in urine .

Pregnancy & Breastfeeding use

Pregnancy: US FDA pregnancy category B. In the animal studies, no evidence of harm to the fetus due to Zetron (Azithromycin) was found. Because animal reproduction studies are not always predictive of human response, Zetron (Azithromycin) should be used during pregnancy only if clearly needed.

Lactation: It is not known whether Zetron (Azithromycin) is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Zetron (Azithromycin) is administered to nursing mother.

Contraindication

Zetron (Azithromycin) is contraindicated in patients hypersensitive to Zetron (Azithromycin) or any other macrolide antibiotic. Co-administration of ergot derivatives and Zetron (Azithromycin) is contraindicated. Zetron (Azithromycin) is contraindicated in patients with hepatic diseases.

Special Warning

Pediatric Use: Zetron (Azithromycin) oral dosage forms can be administered to pediatric patients from 6 months of age. Safety and effectiveness of azithromycin for injection in children or adolescents under 16 years have not been established.

Acute Overdose

There are no data available on overdose with Zetron (Azithromycin). Typical symptoms of overdosage with macrolide antibiotics include hearing loss, severe nausea, vomiting and diarrhoea. Gastric lavage and general supportive measures are indicated.

Interaction with other Medicine

Peak serum levels but not the total extent of absorption were reduced by the presence of magnesium and aluminum-containing antacids. Zetron (Azithromycin) should be taken at least 1 hr before or 2 hrs after these antacids. In patients receiving ergot alkaloids, Zetron (Azithromycin) should be avoided concurrently because of the possibilty of ergotism result in from interaction of Zetron (Azithromycin) with the cytochrome P-450 system However, no cases of such interaction have been reported. Macrolides have been known to increase the plasma concentration of digoxin and cyclosporine. Therefore, if co-administration is necessary caution should be exercised and serum levels of digoxin and cyclosporine should be checked. There have been no pharmacokinetic drug interactions between Zetron (Azithromycin) and warfarin, theophylline, carbamazepine, methylprednisolone and cimetidine.

Storage Condition

Zetron (Azithromycin) IV infusion: When diluted according to the instructions, azithromycin for injection is stable for 24 hours at or below room temperature 30° C, or for 7 days if stored under refrigeration 5° C.

Zetron (Azithromycin) capsule, tablet and dry powder for suspension: should be stored at room temperature (below 30° C). Any unused portion of reconstituted Zetron (Azithromycin) suspension should be discarded after 5 days.

Zetron (Azithromycin) eye drops: Store unopened bottle under refrigeration at 2°C to 8°C. Once the bottle is opened, store at 2°C to 25°C for up to 14 days. Discard after the 14 days.

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