Oral doxycycline reduces pterygium lesions; results from a double blind, randomized, placebo controlled clinical trial

Abstract

Purpose: To determine whether oral doxycycline treatment reduces pterygium lesions.

Design: Double blind, randomized, placebo controlled clinical trial.

Participants: 98 adult patients with primary pterygium.

Methods: Patients were randomly assigned to receive 100 mg oral doxycycline twice a day (49 subjects), or placebo (49 subjects), for 30 days. Photographs of the lesion were taken at the time of recruitment and at the end of the treatment. Follow-up sessions were performed 6 and 12 months post-treatment. Statistical analyses for both continuous and categorical variables were applied. p values of less than 0.05 were considered to indicate statistical significance.

Main outcome measures: The primary endpoint was the change in lesion size after 30 days of treatment.

Results: The primary endpoint was not met for the whole population but subgroup analysis showed that doxycycline was effective in patients of Caucasian origin while other ethnicities, mostly Hispanic, did not respond to the treatment. Moreover, there was a correlation between age and better response (p = 0.003). Adverse events were uncommon, mild, and in agreement with previous reports on short doxycycline treatments.

Conclusions: Oral doxycycline was superior to placebo for the treatment of primary pterygia in older Caucasian patients. These findings support the use of doxycycline for pterygium treatment in particular populations.

Trial registration: European Union Clinical Trials Register EudraCT 2008-007178-39.

Figure 1. Consort flow diagram.

The major reasons for not meeting the inclusion criteria were pregnancy (8) and being on a treatment with doxycycline incompatible drugs (6). Many patients were lost to follow-up probably due to the high number of immigrants, a very mobile population, that were enrolled in the trial. Six patients had to suspend treatment due to mild adverse events. Several patients had more than one pterygium, so the total number of pterygia is also included.

Figure 2. Photographs of the eye of patient number 20 (male, 61 year-old, Caucasian) before (A) and after (B) the treatment with doxycycline for 30 days.

A clear reduction of the lesion's size can be appreciated, from 5.44 mm² to 3.95 mm².

Figure 3. Correlation plot between patient's age (abscises) and relative response to treatment (ordinates) for patients that received either placebo (green circles) or doxycycline (red squares).

The green and red lines represent the correlation slope for each set. There is a significant correlation for doxycycline treatment (Spearman's r = −0.4783, 95% CI −0.7025 to −0.1678, p = 0.003). Relative change in surface is the quotient between the size of the lesion in the second visit divided by the size in the first visit.

Figure 4. Waterfall representation of the relative changes in pterygium surface for all intention-to-treat patients treated with placebo (A, C) or with doxycycline (B, D), according to race.

Each bar represents an individual pterygium. To comply with waterfall representation conventions, values are represented as relative change in surface minus 1, so that positive values represent lesion growth and negative values represent lesion reduction.