Plasma and sputum erythromycin concentrations in chronic bronchitis

Area of Science:

• Pharmacology
• Respiratory Medicine
• Infectious Diseases

Background:

• Chronic bronchitis is a significant respiratory illness often requiring antibiotic treatment.
• Erythromycin is a macrolide antibiotic used for respiratory tract infections.
• Optimizing antibiotic delivery to respiratory tissues is crucial for treatment efficacy.

Purpose of the Study:

• To evaluate plasma and sputum concentrations of a new erythromycin stearate formulation.
• To assess the gastrointestinal absorption and tissue penetration of erythromycin in chronic bronchitis patients.
• To compare drug concentrations with minimal inhibitory concentrations (MICs) for relevant pathogens.

Main Methods:

• 10 patients with chronic bronchitis received an eight-day course of erythromycin stearate.
• Plasma and sputum samples were collected to measure erythromycin concentrations.
• Drug levels were compared to MICs for common respiratory pathogens.

Main Results:

• Plasma erythromycin levels were favorable compared to MICs, indicating good absorption when taken before food.
• Sputum erythromycin levels were highly variable, often low or undetectable.
• Measurable sputum levels were ~10% of plasma levels, with no accumulation observed.
• Sputum concentrations were generally similar to MICs, except for Haemophilus influenzae.
• No correlation found between sputum and plasma levels; trends suggested higher sputum levels with increased pus and plasma concentrations.

Conclusions:

• The new erythromycin stearate formulation demonstrates adequate gastrointestinal absorption.
• Variable sputum penetration may limit efficacy against certain respiratory pathogens in chronic bronchitis.
• Further research is needed to optimize erythromycin delivery to lung tissues for chronic bronchitis treatment.