DALACIN T Topical solution Ref.[6727] Active ingredients: Clindamycin

Pharmacotherapeutic group: Anti-infectives for treatment of acne
ATC Code: DA10AF01

Mechanism of action

Clindamycin is a lincosamide antibiotic that inhibits bacterial protein synthesis. It binds to the 50S ribosomal subunit and affects both ribosome assembly and the translation process. Although clindamycin phosphate is inactive in vitro, rapid in vivo hydrolysis converts this compound to the antibacterially active clindamycin.

Clindamycin has been shown to have in vitro activity against isolates of the following organisms;

Anaerobic gram positive non spore forming bacilli, including:

Propionibacterium acnes.

Pharmacodynamic effects

Efficacy is related to the time period that the agent level is above the minimum inhibitory concentration (MIC) of the pathogen (%T/MIC).

Resistance

Resistance to clindamycin in Propionibacterium acnes can be caused by mutations at the rRNA antibiotic binding site or by methylation of specific nucleotides in the 23S RNA of the 50S ribosomal subunit. These alterations can determine cross resistance to macrolides and streptogramins B (MLSB phenotype). Macrolide-resistant isolates should be tested for inducible resistance to clindamycin using the D zone test.

The prevalence of acquired resistance may vary geographically and with time for selected species and local information on resistance is desirable, particularly when treating severe infections. As necessary, expert advice should be sought when the local prevalence of resistance is such that the utility of the agent in at least some types of infections is questionable. Particularly in severe infections or therapy failure microbiological diagnosis with verification of the pathogen and its susceptibility to clindamycin is recommended.

Resistance is usually defined by susceptibility interpretive criteria (breakpoints) established by EUCAST for systemically administered antibiotics. These breakpoints may be less relevant for topically administered clindamycin. Although clindamycin is not specifically cited, EUCAST has suggested that, for topically applied antimicrobials, resistance might be better defined by epidemiological cut-off values (ECOFFS) rather than the clinical breakpoints determined for systemic administration. However, MIC distributions and ECOFFS have not been published by EUCAST for P. acnes. Based on correlations between clinical results in acne patients and the clindamycin MICs for their P. acnes isolates, values as high as 256 mg/L are considered susceptible for topically administered clindamycin.

A Belgian surveillance study (2011-2012) of anaerobic bacteria included 22 P. acnes isolates; 95.5% were susceptible to clindamycin. An earlier European surveillance study, which included 304 isolates of P. acnes, had reported a resistance rate of 15% to clindamycin. However, this study used a breakpoint of 0.12 mg/L; using the current breakpoint of 4 mg/L, there were no resistant isolates.

Breakpoints

EUCAST breakpoints for Gram-positive anaerobes are listed below. These breakpoints are based on use in systemic infections.

EUCAST Breakpoints for Systemically Administered Clindamycin:

In a U.S. surveillance study, clindamycin MICs were ≤4 mg/L for 97% of P. acnes isolates tested.

In some bacterial species, cross resistance has been demonstrated in vitro among lincosamides, macrolides, and streptogramins B.

Clinical efficacy and safety

P. acnes produces an extracellular lipase that hydrolyses sebum triglycerides to glycerol, used by the organism as a growth substrate, and free fatty acids, which have pro-inflammatory and comedogenic properties. A double-blind study had been conducted to examine the effect of topical 1% clindamycin hydrochloride hydrate in a hydroalcoholic vehicle as compared to the effect of the vehicle alone. Fourteen patients applied clindamycin or vehicle alone twice daily for eight weeks. Free fatty acid surface lipid percentages, quantitative bacterial counts, and clinical response were assessed every two weeks. A significant reduction (88%) in the percentage of free fatty acids in the surface lipids was seen in the clindamycin-treated group and not in the vehicle-treated group. Free fatty acids on the skin surface have been decreased from approximately 14% to 2% following application of clindamycin solution in a hydroalcoholic base to 9 patients (average age 22.3 years) with acne vulgaris. There was no significant change in the surface microflora. Despite the short duration of treatment, objective clinical improvement was seen in three of nine treated patients, while none was observed in the placebo-treated patients.