Zinc a zero: Rosacea unresponsive to dietary supplementation, trial indicates

December 1, 2009

A recent clinical trial found that the dietary supplementation of oral zinc sulfate is ineffective in treating patients suffering from moderate-to-severe rosacea. The apparent failure of this particular clinical trial is of particular interest in that it was a near-duplicate of a 3-year-old clinical trial found in the literature, which showed that oral zinc supplementation was beneficial in the treatment of rosacea.

Key Points

Duluth, Minn. - A recent clinical trial found that the dietary supplementation of oral zinc sulfate is ineffective in treating patients suffering from moderate-to-severe rosacea. The apparent failure of this particular clinical trial is of particular interest in that it was a near-duplicate of a 3-year-old clinical trial found in the literature, which showed that oral zinc supplementation was beneficial in the treatment of rosacea.

According to one expert, the stark discrepancy of the results of this trial when compared to the results of the near-identical trial found in the literature leaves unanswered questions, including the reliability of patient specifics documented in clinical trials.

Therapeutic approaches

Oral zinc supplementation is proven to be helpful in a variety of dermatologic conditions, particularly in the treatment of acne. In an attempt to confirm just how effective oral zinc sulfate is in the treatment of rosacea, Joel T.M. Bamford, M.D., department of dermatology and research, SMDC, Duluth, Minn., and colleagues, conducted a prospective, double-blind, randomized, placebo-controlled clinical trial comparing the efficacy of oral zinc to placebo in patients with moderate-to-severe rosacea.

The study was originally designed to include 80 patients with moderate-to-severe rosacea, with each patient either receiving a twice-daily 220 mg oral dose of zinc sulfate (101.6 mg elemental zinc per day) or placebo for 90 days. Beginning and end of therapy evaluations included quality of life, photographs, blood samples (zinc, copper and hemoglobin levels) and improvement in severity of rosacea.

The results of the interim data analysis of 53 patients showed that zinc sulfate was ineffective in improving rosacea, witnessed in the pre- and post-rosacea severity scores and, therefore, the trial was discontinued. The blood zinc level of patients who received the supplement increased, and changes in ceruloplasmin were seen, suggesting that they had, in fact, received zinc supplements, but no improvements in rosacea were observed.

"It is puzzling why the supplementation of oral zinc sulfate showed to be ineffective in improving rosacea in our patients, especially after near-duplicating a trial from Khalifa E. Sharquie, Ph.D. (Sharquie; Int J Dermatol. 45(7):857-861, July 2006), in which zinc sulfate was found to significantly improve rosacea. Was there a dietary, ethnic or other confounding factor? In his trial, I do not think that the question was asked as to whether these patients were zinc deficient or not at baseline, and some distinction in the trial patient populations may explain the difference in trial outcomes," Dr. Bamford tells Dermatology Times.

Challenges

According to Dr. Bamford, one of the challenges at hand is how one can verify the research results that one achieved in a clinical trial. In order to achieve reliable and reproducible evidence, on which to base practice decisions, the Cochrane review and some journal editors have suggested that documentation of the study protocols be published before any study is initiated.

If this new approach were to be taken, study methods and design of future trials could possibly receive a wave of scrutiny and constructive criticism from colleagues. Dr. Bamford says this would also help to avoid any "cherry-picking" of studies, reporting only on positive outcomes, and would assist those trying to confirm findings, as in their study.

"I hope that dermatologists would look at this poster/abstract report and Sharquie's peer-reviewed published article to think out other ways, confounding factors, why this study culminated in failure to confirm their results," Dr. Bamford says.

Disclosure: Dr. Bamford reports no relevant financial interests.