A Phase I Determination of Azithromycin in Plasma during a 6-Week Period in Normal Volunteers after a Standard Dose of 500mg Once Daily for 3 Days

Authors: Crokaert F.¹; Hubloux A.²; Cauchie P.²

Source: Clinical Drug Investigation, Volume 16, Number 2, 1 August 1998 , pp. 161-166(6)

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Abstract:

Objectives: The pharmacokinetics of azithromycin were evaluated in 12 healthy volunteers.

Methods: This was an open study in 12 healthy male subjects. Participants received a single dose of 2 × 250mg azithromycin (two azithromycin capsules) administered orally in the fasting state with 240ml water on three consecutive days.

Results: After oral intake of two capsules of 250mg azithromycin over three consecutive days (the normal treatment regimen in adults), azithromycin was present in measurable levels in plasma (>5 µg/L) for 7 to 17 days after the beginning of treatment. The apparent elimination half-life was very long (observed range: 49 to 108 hours, i.e. about 2 to 4.5 days). From the results in plasma, one can extrapolate that the azithromycin concentration would remain above 1 µg/L (corresponding to concentrations in tissues above 0.1 mg/L) for up to 15 to 30 days following treatment. The elimination half-life of azithromycin (average of 76 hours) was in agreement with values of depletion rates in tissues corresponding to a half-life of 60 to 72 hours.

Conclusion: In conclusion, the utility of the long exposure of patients with benign respiratory infections to azithromycin and to subinhibitory concentrations of azithromycin should be questioned.

Keywords: Azithromycin, pharmacokinetics; Clinical-pharmacokinetics; Antibacterials, pharmacokinetics

Document Type: Original article

Affiliations: 1: Institut Jules Bordet, Brussels, Belgium 2: Abbott, Louvain-la-Neuve, Belgium

Publication date: 1998-08-01