Systemic absorption of clindamycin was estimated following a once-a-day intravaginal dose of one clindamycin phosphate vaginal suppository (equivalent to 100 mg clindamycin) administered to 11 healthy female volunteers for 3 days. Approximately 30% (range 6% to 70%) of the administered dose was absorbed systemically on day 3 of dosing based on area under the concentration-time curve (AUC). Systemic absorption was estimated using a subtherapeutic 100 mg intravenous dose of clindamycin phosphate as a comparator in the same volunteers. The mean AUC following day 3 of dosing with the suppository was 3.2 µg•hr/mL (range 0.42 to 11 µg•hr/mL). The Cmax observed on day 3 of dosing with the suppository averaged 0.27 µg/mL (range 0.03 to 0.67 µg/mL) and was observed about 5 hours after dosing (range 1 to 10 hours). In contrast, the AUC and Cmax after the single intravenous dose averaged 11 µg•hr/mL (range 5.1 to 26 µg•hr/mL) and 3.7 µg/mL (range 2.4 to 5.0 µg/mL), respectively. The mean apparent elimination half-life after dosing with the suppository was 11 hours (range 4 to 35 hours) and is considered to be limited by the absorption rate.
The results from this study showed that systemic exposure to clindamycin (based on AUC) from the suppository was, on average, three fold lower than that from a single subtherapeutic 100 mg intravenous dose of clindamycin. In addition, the recommended daily and total doses of intravaginal clindamycin suppository are far lower than those typically administered in oral or parenteral clindamycin therapy (100 mg of clindamycin per day for 3 days equivalent to about 30 mg absorbed per day from the ovule relative to 600 to 2700 mg/day for up to 10 days or more, orally or parenterally). The overall systemic exposure to clindamycin from Cleocin Vaginal Ovules is substantially lower than the systemic exposure from therapeutic doses of oral clindamycin hydrochloride (two-fold to 20-fold lower) or parenteral clindamycin phosphate (40-fold to 50-fold lower).
Clindamycin inhibits bacterial protein synthesis at the level of the bacterial ribosome. The antibiotic binds preferentially to the 50S ribosomal subunit and affects the process of peptide chain initiation. Although clindamycin phosphate is inactive in vitro, rapid in vivo hydrolysis converts this compound to the antibacterially active clindamycin.
Culture and sensitivity testing of bacteria are not routinely performed to establish the diagnosis of bacterial vaginosis. (See INDICATIONS AND USAGE.) Standard methodology for the susceptibility testing of the potential bacterial vaginosis pathogens, Gardnerella vaginalis, Mobiluncus spp, or Mycoplasma hominis, has not been defined. Nonetheless, clindamycin is an antimicrobial agent active in vitro against most strains of the following organisms that have been reported to be associated with bacterial vaginosis:
- Bacteroides spp
- Gardnerella vaginalis
- Mobiluncus spp
- Mycoplasma hominis
- Peptostreptococcus spp