Pharmacokinetics and tolerability of a single oral 600-mg dose of doxycycline.

The pharmacokinetics of a single orally administered 600-mg dose of doxycycline (six 100-mg film-coated tablets) was studied in 18 healthy subjects. Plasma doxycycline levels remained above 1.35 mumol/L for 48 hours and compared favourably with the mean inhibitory concentrations of doxycycline against the common infecting organisms in chronic bronchitis. In a separate tolerability study in 37 healthy subjects, there was no significant difference between doxycycline and placebo in the incidence of adverse effects.