Q&A

Low-dose doxycycline moderately effective for acne

J Fam Pract. 2003 August;52(8):587-604
By
Seth T. Miller, MD
James J. Stevermer, MD, MSPH
Author and Disclosure Information

  • BACKGROUND: Doxycycline, when used in doses that are below its antimicrobial threshold, is effective in treating adult chronic periodontitis. Doxycycline hyclate 20 mg twice daily (Periostat) is believed to work by decreasing inflammation and does not appear to create bacterial resistance to itself. Given the role of host inflammatory response in acne, the researchers tested sub-antimicrobial dosing of doxycycline in adults with moderate acne.
  • POPULATION STUDIED: The subjects were 51 adults with moderate acne (defined as 6–200 comedones, 10–75 papules, and <6 nodules) drawn from 2 university-based outpatient clinics. Thirty-five (69%) were white, and the mean age was 23 years.
  • STUDY DESIGN AND VALIDITY: In this double-blind randomized study, patients were given either oral doxycycline hyclate 20 mg twice daily (n=26) or a matching placebo (n=25). Patients were assessed at baseline and at 2, 4, and 6 months.
  • OUTCOMES MEASURED: The primary outcomes measured were the number of lesions present at each evaluation. Secondary outcomes included the clinician global assessment and the patient self-assessment scores using a 7-point qualitative scale. Forehead skin flora samples were collected at baseline and at 6 months to assess for changes in microflora or resistance patterns.
  • RESULTS Six months after baseline, the doxycycline group showed a greater decrease in inflammatory lesions (50.4% fewer vs 30.2% fewer for placebo; P=.04) and comedones (53.6% fewer vs 10.6% fewer; P=.01). The clinician’s global assessment, however, was an improvement of only 0.4 on a 7-point scale at 6 months, a barely clinically significant difference (P=0.03). The change in patients’ global assessment was also towards improvement, but was not statistically significant.
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PRACTICE RECOMMENDATIONS

The authors propose that moderate acne may be treated with doxycycline in subantimicrobial doses (20-mg tablets taken twice daily). This regimen was well-tolerated, moderately effective in reducing skin lesions, and did not have a detectable effect on the antibiotic resistance of skin flora.

The cost of Periostat (the only form of doxycycline 20 mg available in the US) is about $55 per month, while generic doxycycline 100 mg is about $10.1 This study has some significant flaws, but a trial of low-dose doxycycline in an adult with acne severe enough to warrant antibiotics would still seem a reasonable, albeit expensive, option.

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