Comparative effectiveness of tetracycline, minocycline and doxycycline in treatment of acute-on-chronic bronchitis. A study based on sputum levels.

After the administration of minocycline, doxycyline and tetracycline in recommended therapeutic doses to 11, 10 and 12 patients respectively, sputum levels of these antibiotics were determined. Only 20% of patients given doxcycline had a satisfactory sputum level and in the remainder levels were either low or absent. For patients receiving tetracycline and minocycline, 67% and 64% respectively had satisfactory sputum levels. Patients selected for this study had a history of chronic bronchitis and were producing copious amounts of purulent sputum. Minimum inhibitory concentrations of these three antibiotics were similar for 25 freshly isolated strains of Haemophilus influenzae, with minocycline being the most inhibitory and doxcycline the least inhibitory.