Telithromycin (HMR 3647) is a novel ketolide antimicrobial with good activity against both common and atypical respiratory pathogens, including many resistant strains. This randomized, three-period crossover study determined the dose proportionality of telithromycin pharmacokinetics after single and multiple dosing in healthy subjects. In each treatment period, subjects received a single oral dose of 400, 800 or 1,600 mg of telithromycin followed 4 days later by the same dose once daily for 7 days. Blood and urine samples were taken throughout the study for determination of pharmacokinetic parameters for telithromycin and RU 76363, its main metabolite. Telithromycin and RU 76363 achieved steady state within 2 to 3 days of once-daily dosing. A slight accumulation of telithromycin was observed after 7 days of therapy, with values of the area under the concentration-time curve from 0 to 24 h approximately 1.5 times higher than those achieved with the single dose. The pharmacokinetics of telithromycin and RU 76363 deviated moderately from dose proportionality. At a dose of 800 mg/day, telithromycin attained mean maximal and trough plasma concentrations of 2.27 and 0.070 mg/liter respectively. Elimination was biphasic; initial and terminal half-lives were 2.87 and 9.81 h for the 800-mg dose. Study medication was well tolerated, although adverse events tended to be more frequent at the 1,600-mg dose. This study showed that telithromycin was generally well tolerated and suggests that a once-daily 800-mg oral dose of telithromycin maintains an effective concentration in plasma for the treatment of respiratory tract infections involving the key respiratory pathogens.

Zinc/clindamycin gel (Zindaclin 1%) gel, is a new once-daily topical acne treatment (Strakan Ltd) containing clindamycin phosphate equivalent to 1% clindamycin and zinc acetate in a formulation, which leads to a reduced systemic absorption of clindamycin through the skin. The objective of the study was to compare the systemic absorption of clindamycin from zinc/clindamycin gel and clindamycin lotion (Dalacin T topical lotion, Pharmacia Ltd) after repeated twice-daily topical administration for two periods of 5 days with an intervening gap of 2 weeks in 24 subjects with mild to moderate acne. Plasma Cmax, and AUC0-12 of clindamycin measured after single and multiple applications of zinc/clindamycin gel were between 30% and 50% lower than for clindamycin lotion. As zinc/clindamycin gel is a topical treatment for acne, the lower systemic bioavailability may be beneficial because there may be a correspondingly lower risk of systemic events in zinc/clindamycin gel-treated subjects.

The penetration of telithromycin (HMR 3647), a novel ketolide antimicrobial, has been assessed in an open, single-dose study in eight healthy male subjects. Following a single, oral, 600 mg dose the mean ratio of the concentration of telithromycin in blister fluid over plasma was 1.38. Significant blister fluid concentrations were maintained up to 24 h post-dose. These results indicate that telithromycin penetrates well into inflammatory extracellular fluid, achieving high and sustained concentrations in this medium.

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