A randomized, double-blind, placebo-controlled trial of the combined effect of doxycycline hyclate 20-mg tablets and metronidazole 0.75% topical lotion in the treatment of rosacea

Background: Subantimicrobial doses of doxycycline may improve outcomes in rosacea when combined with topical metronidazole and used as maintenance monotherapy. Objective: The purpose of this Study was to evaluate the safety and efficacy of doxycycline hyclate 20 mg (subantimicrobial dose doxycycline) administered twice daily as an adjunct to metronidazole 0.75% topical lotion in the treatment of rosacea. Methods: Patients received subantimicrobial doses of doxycycline twice daily Plus metronidazole (n = 20) or placebo plus metronidazole (n = 20) for 12 weeks. Subantimicrobial-dose doxycycline or placebo monotherapy continued for 4 weeks. The primary efficacy measure was change from baseline in total inflammatory lesions at weeks 2 and 16. Results: Total inflammatory lesions were reduced significantly (P =.048) by week 4 and by all subsequent visits in the subantimicrobial-dose doxycycline/metronidazole group compared with placebo/ metronidazole. Changes from baseline increased over time and were maintained during subantimicrobialdose doxycycline monotherapy. Conclusion: Adjunctive use of subantimicrobial dose doxycycline significandy reduced the clinical signs of rosacea compared with metronidazole alone and may be useful maintenance monotherapy.