By Perrie Susman
MIAMI BEACH, Fla -- March 9, 2010 -- Adapalene-benzoyl peroxide ointment plus doxycycline is effective in reducing colonisation of Propionibacterium acnes, researchers said here on March 7 at the 68th Annual Meeting of the American Academy of Dermatology (AAD).
P acnes is believed to play a major role in the pathogenesis of acne, according to Michael Jarratt, MD, DermResearch, Inc., Austin, Texas.
Dr. Jarratt and colleagues randomised 459 patients to study the safety and effectiveness of adapalene-benzoyl peroxide ointment and doxycycline to a vehicle gel and doxycycline.
Dr. Jarratt reported on the results of 38 of the patients, of whom 18 were treated with adapalene plus doxycycline and 20 with only with doxycycline, and all underwent fluorescence photoimaging.
"Ultraviolet fluorescence photography provided an evaluation of the presence of P acnes, which has been shown to be correlated with the intensity of orange red fluorescence from its metabolites," Dr. Jarratt reported. "This reliable, quick, and practical method measures the total spot area, or number of pixels associated with ultraviolet fluorescent spots, and when reduced has been found to correlate well with the decrease in presence of P acnes from scrub cultures."
Although this method cannot detect slight changes in the condition, it is reliable with large variations, which are more likely to be quantitatively relevant, he continued.
After the first 4 weeks of treatment, the researchers found a reduction of 60.3% in P acnes in the adapalene-doxycycline group versus 22% reduction in the vehicle group.
Most topical anti-acne drugs and topical antibiotics produce therapeutic effect through the elimination of P acnes. Some strains are resistant to antibiotics as a result of topical and systemic antibiotic usage.
"Adapalene-benzoyl peroxide ointment is a unique, antibiotic-free combination of a well-tolerated topical retinoid and a well-established antimicrobial agent at a low concentration," Dr. Jarratt said.
He explained that the reduction in P acnes seen in this subgroup correlates well with the improved lesion reduction and clinical benefit observed in the adapalene-doxycycline group compared with the vehicle-doxycycline group as part of the main study's primary endpoint.
"Taken together, these data suggest that adapalene-benzoyl peroxide ointment plus doxycycline is an effective regimen whose mechanism may be partly related to a decrease in P acnes on the skin," he said.
Funding for this study was provided by Galderma Laboratories.
[Presentation title: Treatment With Adapalene 0.1%-BPO 2.5% and Doxycycline 100 mg/day Resulted in Rapid and Sustained Decrease in Propionibacterium acnes. Abstract P102]
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