INDO 500

Indications

• Bacterial infections of the respiratory tract
• Skin and soft tissue infections
• Chlamydia infections
• Legionnaires' disease
• Pertussis (whooping cough)
• Mycoplasma pneumonia
• Acne vulgaris (as part of combination therapy)

Dosage

Children: Refer to the BNF for Children for appropriate dosing in paediatric patients.

Adults: Refer to the specific guidelines or BNF for appropriate dosing regimens based on the infection being treated.

Mechanism of action

Erythromycin exerts its antibacterial effects by binding to the 50S subunit of the bacterial ribosome. This binding inhibits the translocation step of protein synthesis, effectively stopping the growth of bacteria. Erythromycin is primarily bacteriostatic, meaning it inhibits bacterial growth rather than killing bacteria outright.

Pharmacodynamics

The primary pharmacodynamic effect of erythromycin is its ability to inhibit bacterial protein synthesis. The drug is effective against many strains of Streptococcus, Staphylococcus, and certain strains of Bacillus, as well as some intracellular pathogens like Chlamydia and Mycoplasma. The efficacy of erythromycin can be influenced by the site of infection, the bacterial strain, and local antibiotic resistance patterns.

Pharmacokinetics

Erythromycin is well absorbed from the gastrointestinal tract, but its bioavailability can be affected by food. It is extensively metabolized in the liver, with a half-life ranging from 1.5 to 2 hours. The drug is excreted primarily in the bile, with some renal excretion. Erythromycin can penetrate tissues well and is often used for respiratory tract infections due to its good distribution in lung tissues.

Contra-indications

• Hypersensitivity to erythromycin or any of its components
• History of cholestatic jaundice or hepatic dysfunction associated with previous erythromycin use
• Concomitant use of certain medications that may lead to life-threatening arrhythmias

Adverse effects

• Gastrointestinal disturbances (nausea, vomiting, diarrhea, abdominal pain)
• Hepatotoxicity (elevated liver enzymes, jaundice)
• Allergic reactions (rash, urticaria, anaphylaxis)
• Ototoxicity (hearing loss, tinnitus)
• Cardiac arrhythmias (QT prolongation)

Interactions

• Increased risk of cardiotoxicity when administered with drugs that prolong the QT interval (e.g., antipsychotics, certain antiarrhythmics)
• Erythromycin may inhibit cytochrome P450 enzymes, affecting the metabolism of drugs like theophylline, warfarin, and statins
• Concomitant use with drugs that are substrates of the P-glycoprotein transporter may alter their effects

Precautions

• Use with caution in patients with liver disease or myasthenia gravis
• Monitor for signs of hepatotoxicity during prolonged therapy
• Assess for potential drug interactions before starting therapy

Pregnancy

Erythromycin is generally considered safe to use during pregnancy. However, it should only be used if clearly needed and after consulting with a healthcare provider.

Breast-feeding

Erythromycin is excreted in breast milk. While generally considered safe, breastfeeding mothers should consult with healthcare providers before use.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Oral tablets
• Oral suspension
• Topical ointment
• Injectable solution