Trimethoprim Alone Compared to Co-trimoxazole in Lower Respiratory Infections: Pharmacokinetics and Clinical Effectiveness

24 patients, admitted to hospital with lower respiratory tract infection, were treated with either co-trimoxazole (800 mg sulphamethoxazole + 160 mg trimethoprim) or trimethoprim (200 mg) orally twice daily. All showed a clinical improvement and with one exception respiratory pathogens were eliminated. Pharmacokinetics in blood, sputum and saliva were studied in 11 patients taking trimethoprim and 9 taking co-trimoxazole. No sulphamethoxazole was detected in either the sputum or saliva. Trimethoprim was found in higher concentrations in the sputum than in the blood, although there were wide and significant variations in individual patient's sputum pharmacokinetic profiles. Trimethoprim penetrates into the sputum at therapeutic concentrations in patients with chronic respiratory infections.