ZMAX

Indications

• Bacterial infections
• Mild to moderate typhoid due to multiple-antibacterial resistant organisms
• Respiratory-tract infections
• Otitis media
• Skin and soft tissue infections
• Chlamydia trachomatis genital infection
• Chronic Pseudomonas aeruginosa infection in cystic fibrosis
• Prevention of group A streptococcal infection in patients allergic to penicillin

Dosage

Children: Child 6 months–17 years: 10 mg/kg once daily (max. per dose 500 mg) for 3 days, repeated after 1 week if necessary. Refer to BNF for Children for specific dosing based on age and weight.

Adults: 500 mg once daily for 3 to 5 days depending on the infection being treated. For certain cases, doses may be adjusted based on clinical judgment.

Mechanism of action

Azithromycin binds to the 50S ribosomal subunit of bacteria, inhibiting protein synthesis and thus preventing bacterial growth.

Pharmacodynamics

Azithromycin exhibits bacteriostatic activity against susceptible bacteria. It has a long half-life, allowing for once-daily dosing and effective treatment of infections.

Pharmacokinetics

Azithromycin is well-absorbed after oral administration, with a bioavailability of approximately 37%. It penetrates well into tissues, with a half-life of about 68 hours, and is primarily excreted in bile, with minimal renal excretion.

Adverse effects

• Appetite decreased
• Diarrhoea
• Dizziness
• Gastrointestinal discomfort
• Headache
• Hearing impairment
• Insomnia
• Nausea
• Pancreatitis
• Paraesthesia
• Skin reactions
• Taste altered
• Vomiting
• Angioedema
• Anxiety
• Arrhythmias
• Chest pain
• Constipation
• Drowsiness
• Eosinophilia
• Hepatic disorders
• Leucopenia
• Neutropenia
• Palpitations
• QT interval prolongation
• Severe cutaneous adverse reactions (SCARs)
• Tinnitus
• Vertigo
• Antibiotic associated colitis
• Myasthenia gravis
• Nephritis tubulointerstitial
• Hallucination
• Hypotension
• Seizure
• Acute kidney injury
• Aggression
• Akathisia
• Hemolytic anemia
• Syncope

Interactions

• Azithromycin + ticagrelor: Moderate (increases exposure)
• Azithromycin + aliskiren: Unknown (increases exposure)
• Azithromycin + aminophylline: Unknown (increases exposure)
• Azithromycin + colchicine: Unknown (increases exposure)
• Azithromycin + erlotinib: Unknown (increases exposure)
• Azithromycin + lomitapide: Unknown (increases exposure)
• Azithromycin + rimegepant: Unknown (increases exposure)
• Azithromycin + taxanes: Unknown (increases exposure)
• Azithromycin + docetaxel: Unknown (increases exposure)
• Azithromycin + paclitaxel: Unknown (increases exposure)

Precautions

• Use with caution in patients with electrolyte disturbances
• Use with caution if estimated glomerular filtration rate is less than 10 mL/minute/1.73 m2
• Predisposition to QT interval prolongation may be aggravated

Indications

• Controlled drug delivery
• Targeted therapy
• Cancer treatment
• Vaccination
• Hormonal therapy

Dosage

Children: Dosing for paediatric patients should be determined based on the specific formulation and the clinical context. Consult relevant guidelines and product information for appropriate dosing.

Adults: Dosing information varies widely based on the specific drug formulation and the clinical condition being treated. Refer to specific product information and clinical guidelines for accurate dosing.

Mechanism of action

Microspheres function primarily by encapsulating drugs within their polymeric matrix. This encapsulation allows for controlled release, protecting the drug from degradation and enhancing its absorption. Depending on the formulation, microspheres can be engineered to release their content in response to specific stimuli, such as pH changes or temperature variations, which aids in targeted therapy.

Pharmacodynamics

The pharmacodynamic properties of microspheres vary depending on the encapsulated drug and the release mechanism. Generally, they improve the pharmacological profile of drugs by prolonging their action, reducing side effects, and allowing for sustained therapeutic concentrations in the target area. This results in enhanced efficacy and safety.

Pharmacokinetics

The pharmacokinetics of microspheres is influenced by their size, composition, and the drug they carry. After administration, they can be absorbed through various routes, including oral, intravenous, or subcutaneous. The release rate of the drug from the microspheres affects its absorption, distribution, metabolism, and excretion. Typically, microspheres are designed to provide a controlled release over a specific period, which can lead to prolonged therapeutic effects and reduced dosing frequency.

Adverse effects

• Injection site reactions
• Local inflammation
• Systemic allergic reactions
• Headache
• Nausea
• Fatigue

Precautions

• Monitor for allergic reactions, especially in patients with known hypersensitivity
• Use with caution in patients with compromised immune systems

Pregnancy

Safety during pregnancy has not been established. Use only if the benefits outweigh the risks.

Breast-feeding

Excretion in breast milk is unknown. Caution is advised when administering to breastfeeding mothers.

Storage

Store at controlled room temperature, away from heat and moisture. Do not freeze.

Formulations

• Microsphere injection
• Microsphere implant

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.