Zithrocin

Azithromycin dihydrate.

Each tablet contains: Azithromycin (as dihydrate) 500 mg.
Azithromycin is an azalide antibiotic, a subclass of macrolide antibiotics. Azalides are distinguished from other macrolides such as erythromycin, by the addition of nitrogen at position 9a of the lactone ring. Azithromycin has a broader spectrum of activity than that of erythromycin or clarithromycin.

Pharmacology: Pharmacodynamics and Pharmacokinetics: Like other macrolides, azithromycin inhibits RNA-dependent protein synthesis by binding to the 50S ribosomal sub unit of the 70S ribosome of susceptible bacteria. The site of action appears to be the same as that of the macrolides, clindamycin, lincomycin, and chloramphenicol. Azithromycin is less active than erythromycin against streptococci and staphylococci, but has greater activity in vitro against some Gram-negative organisms such as Haemaphilus influenzae and Moraxella catarrhalis (Branhamella catarrhalis), as well as having activity against same of the Enterabacteriaceae such as Escherichia coli, Salmonella and Shigella spp. Azithromycin is also more active than erythromycin against Chlamydia trachomatis and Ureaplasma urealyticum and same opportunistic mycobacteria including Mycobacterium avium complex. Azithromycin is active against the protozoa Taxoplasma gondii and Plasmodium falciparum.
Azithramycin is rapidly absorbed after oral intake and achieves peak plasma concentration in about 2-3 hours. Azithromycin is extensive distributed into the tissues and there is little diffusion into the CSF when the meninges are not inflamed. Excretion is main in bile as an unchanged drug it has terminal elimination half-life of about 68 hours.

Azithromycin is indicated for the treatment of mild to moderate infections caused by susceptible organisms: such as respiratory tract infections, uncomplicated skin and soft tissue infections, uncomplicated genital infections chlamydial infections and non-gonococcal urethritis, chancroid and pelvic inflammatory diseases.

Azithromycin should be administered as a single dose, with or without food.
For all indications other than sexually transmitted diseases, the total dose is 1.5 g, which should be given as 500 mg daily for 3 days. Alternatively an initial dose of 500 mg may be followed by 250 mg daily for 4 days.
For uncomplicated sexually transmitted disease caused by Chlamydia trachomatis the dose is 1 g given as a single dose. A single dose of 2 g has been given for uncomplicated gonorrhea.
For prophylaxis of disseminated MAC infections, azithromycin 1.2 g maybe given once weekly. For treatment or secondary prophylaxis, 500 mg once daily should be given with other antimycobacterials.
For mild to moderate typhoid caused by multidrug resistant strains, 500 mg once daily maybe given for 7 days.
Or as prescribed by the physician.

Treatment of overdosage is symptomatic and supportive. Dysrhythmias should be treated with appropriate antiarrhythmic drugs.
Gastric lavage and general supportive measures are indicated as required.

Azithromycin is contraindicated in patients with known hypersensitivity to azithromycin, erythromycin, or any macrolide antibiotics.

Use of azithromycin should be avoided in patients with hepatic function impairment because biliary excretion is the major route of elimination for azithromycin. It should also be used with caution in patients with renal impairment.

Reproduction studies done in animals given azithromycin at doses up to moderately maternal toxic dose have found no evidence of harm to the fetus. There are no adequate and well-controlled studies done in pregnant and nursing women. Azithromycin has been detected in human milk. Caution should be exercised when administering azithromycin to nursing women.

Most frequent adverse effects are gastrointestinal in origin with anorexia, nausea, abdominal discomfort, cramps, flatulence, vomiting and diarrhea. Adverse effects also include pruritus, urticaria, skin rashes as well as occasional cases of anaphylaxis. Stevens-Johnson syndrome and toxic epidermal necrosis have also been reported very rarely. Thrombocytopenia and mild transient neutropenia have been rarely reported in patients taking azithromycin. Azithromycin may aggravate muscle weakness in patients with myasthenia gravis. Other side effects reported include chest pain, melena, vaginitis, headache, taste disturbances, vertigo, dizziness, convulsions, somnolence, tinnitus and fatigue.
Azithromycin may cause reversible sensorineural hearing loss, eosinophilia, acute interstitial nephritis. Effects on fluid and electrolyte homeostasis have also been reported.
Azithromycin like other macrolides, may cause irregular heart beat. Patients at particular risk are those with history of existing QT interval prolongation, low blood levels of potassium or magnesium, and those taking certain drugs used to treat arrythmias.

Azithromycin may interact with antacids containing aluminum or magnesium salts and should be given at least an hour before or 2 hours after the antacid. Erythromycin and other macrolides have the potential to interact with a large number of drugs through their action on the hepatic cytochrome P450 isoenzymes, particular CYP1A2 and CYP3A4. These interactions can result in severe adverse effects, including ventricular arrhythmias with astemizole, cisapride and tertenadine. Other macrolides including azithromycin and dirithromycin are reported to have little or no effect on hepatic cytochrome, and consequently may produce fewer drug interactions.
Other mechanisms by which macrolides cause interactions include suppression of the gastrointestinal flora responsible for the inhaluminal metabolism of digoxin and possibly oral contraceptives, and the stimulant effect of macrolides on gastrointestinal motility which is believed to be responsible for the interaction between spiramycin and levodapa.
Serum concentrations of azithromycin are markedly increased when it is administered with nelfinavir, but the clinical significance of this is uncertain. Although dosage adjustment is not required the patient should be close monitored for adverse effects.
Macrolides have been reported rare to prolong the QT interval and should be used with caution with other drugs known to also have this effect.
Azithromycin may also interact with zidovudine, ergot derivates, coumarin and ciclosporin. Caution should be exercised before considering administration with these drugs.

Store at temperatures not exceeding 30°C.

Macrolides

J01FA10 - azithromycin ; Belongs to the class of macrolides. Used in the systemic treatment of infections.

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