Study of the pharmacokinetics of levofloxacin when combined with st. John’s wort preparations in healthy volunteers and in patients with lower respiratory tract infection

In patients with pneumonia and concomitant diseases, the administration of antimicrobial agents together with other medications accompanied by the risk of side effects and drug-drug interactions. We studied the pharmacokinetics (PK) of levofloxacin when combined with a herbal preparation (common St. John’s wort extract) in healthy volunteers and in patients with community-acquired pneumonia on the days 1 and 5 of the drugs intake. Individual differences in the average concentrations (AUC analog) of the antibiotic before and after the course of administration of the St. John’s wort extract within each group were quite significant; however, the group-average differences were statistically insignificant. Intergroup differences in PK with St. John’s wort intake were also statistically insignificant. To search for factors that make a significant contribution to the variations observed in PK indices, we used a statistical multivariate analysis of variance which included factors such as gender, age, body mass index, smoking history, and cardiovascular system parameters. We found that smoking only and, to a lesser extent, the patient’s gender had an effect on levofloxacin PK, while the intake of St. John’s wort completely eliminated this effect. Other factors played an insignificant role in the antibiotic PK regardless of the St. John’s wort administration.