AZYLYM TABLETS

Indications

• Community-acquired pneumonia
• Acute bacterial sinusitis
• Skin and soft tissue infections
• Chlamydia infections
• Gonorrhea
• Pharyngitis and tonsillitis
• Acne vulgaris
• Chronic obstructive pulmonary disease exacerbations

Dosage

Children: For children, dosing varies by indication and weight. Refer to the BNF for Children for specific dosing recommendations based on the child's age and condition.

Adults: The usual adult dosage is 500 mg on the first day, followed by 250 mg once daily for the next 4 days. In the treatment of certain infections, refer to specific guidelines and the BNF for precise dosing adjustments.

Mechanism of action

Azithromycin binds to the 23S rRNA of the bacterial 50S ribosomal subunit. This binding inhibits the transpeptidation/translocation step of protein synthesis and prevents the assembly of the 50S ribosomal subunit, leading to the inhibition of polypeptide synthesis. While primarily bacteriostatic, it can exhibit bactericidal activity against certain organisms at high concentrations.

Pharmacodynamics

Azithromycin exhibits broad-spectrum antibacterial activity by inhibiting protein synthesis and translation. It has immunomodulatory effects, which can be beneficial in treating chronic respiratory inflammatory diseases. Its pharmacological profile allows it to effectively manage various bacterial infections.

Pharmacokinetics

Azithromycin has a long half-life and is characterized by extensive tissue distribution. It concentrates in phagocytes and is primarily eliminated through biliary excretion. The drug's stability at low pH enhances its bioavailability, and it is known to maintain effective concentrations in tissues for extended periods.

Adverse effects

• nausea
• vomiting
• diarrhea
• abdominal pain
• anorexia
• rash
• headache
• dizziness
• hearing loss
• QT interval prolongation

Interactions

• Antacids containing aluminum or magnesium may reduce the absorption of azithromycin.
• CYP3A4 inducers (e.g., rifampicin, carbamazepine) may decrease azithromycin effectiveness.
• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin) may increase azithromycin levels.

Precautions

• Use with caution in patients with hepatic impairment.
• Monitor for signs of superinfection due to prolonged use.
• Assess for potential QT prolongation in patients with cardiac conditions.

Pregnancy

Azithromycin is classified as category B. Animal reproduction studies have not demonstrated a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women.

Breast-feeding

Azithromycin is excreted in breast milk. Caution is advised when administering to nursing mothers.

Storage

Store at room temperature (15-30°C). Protect from light and moisture.

Formulations

• Tablets (250 mg, 500 mg)
• Oral suspension (100 mg/5 mL, 200 mg/5 mL)
• Injectable solution (500 mg)

Mechanism of action

In order to replicate, bacteria require a specific process of protein synthesis, enabled by ribosomal proteins. 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. Azithromycin is highly stable at a low pH, giving it a longer serum half-life and increasing its concentrations in tissues compared to erythromycin. Azithromycin usually is bacteriostatic, although the drug may be bactericidal in high concentrations against selected organisms. Bactericidal activity has been observed in vitro against Streptococcus pyogenes, S. pneumoniae, and Haemophilus influenzae. Azithromycin inhibits protein synthesis in susceptible organisms by penetrating the cell wall and binding to 50S ribosomal subunits, thereby inhibiting translocation of aminoacyl transfer-RNA and inhibiting polypeptide synthesis. The site of action of azithromycin appears to be the same as that of the macrolides (i.e., erythromycin, clarithromycin), clindamycin, lincomycin, and chloramphenicol. The antimicrobial activity of azithromycin is reduced at low pH. Azithromycin concentrates in phagocytes, including polymorphonuclear leukocytes, monocytes, macrophages, and fibroblasts. Penetration of the drug into phagocytic cells is necessary for activity against intracellular pathogens (e.g., Staphylococcus aureus, Legionella pneumophila, Chlamydia trachomatis, Salmonella typhi).

Pharmacodynamics

Macrolides stop bacterial growth by inhibiting protein synthesis and translation, treating bacterial infections. Azithromycin has additional immunomodulatory effects and has been used in chronic respiratory inflammatory diseases for this purpose.