This was a randomized, single-blind, controlled clinical trial, comparing the efficacy of ivermectin and combined therapy with ivermectin–metronidazole in the treatment of anterior blepharitis and skin lesions of D. folliculorum.

This study took place in the Dermatology and Ophthalmology Clinic of the Mansoura University Hospitals between June 2011 and February 2012.

One hundred twenty patients were enrolled (mean age 36.71?±?12.4 years) and categorized into four groups of 30 patients each (patients with acne vulgaris, rosacea, peri-oral dermatitis, and anterior blepharitis).

The selection criteria for patients with skin lesions were: a treatment-resistant infestation, with D. folliculorum mite density >5 mites/cm².

The potential criteria for the diagnosis of Demodex blepharitis are summarized as follows:¹⁶ (1) clinical history: high index of suspicion when blepharitis is refractory to conventional treatments, or when there is madarosis or recurrent trichiasis; (2) slit-lamp examination: typical cylindrical dandruff at the root of eyelashes; (3) microscopic confirmation: detection and counting of Demodex mites in epilated lashes.

Patients with a mite density ?5 mites/cm² for skin lesions or with <3 living mites/eyelash, a history of systemic or topical antibacterial or anti-inflammatory drugs in the 60 days before study entry, those with a known hypersensitivity to ivermectin or metronidazole, and pregnant women were excluded. In patients with anterior blepharitis, we also excluded those with posterior or mixed blepharitis, contact lenses, meibomian gland dysfunction, and any previous eye surgery.

Informed consent was obtained from each of the participants, and the study was performed in accordance with the principles of our institutional ethics committee.

At the time this study was designed there were insufficient data to perform a reliable sample size calculation. So we anticipated that two groups of 60 patients each would be sufficient to indicate efficacy of the two regimens at 4 weeks. Based on the outcome of this pilot study, we will design a larger randomized controlled trial, including a large number of patients, based on a power calculation.

The 120 participants were randomly assigned to either combined therapy or ivermectin treatment at a ratio of 1:1 (15 patients for each treatment regimen from each group) using a computer-generated randomization schedule. The assignment was done in a single-blinded manner, in which the subjects were blinded to the treatment assignment.

Since metronidazole has an anti-inflammatory and acaricidal action, it is expected to have a better effect in combination with ivermectin and improve the outcome of treated patients.

In each group 15 patients received combined therapy with metronidazole (does 250?mg three times per day for 2 weeks) and ivermectin (two doses of 200??g/kg, 1 week apart), and 15 patients received ivermectin alone (two doses of 200??g/kg, 1 week apart). All patients were then followed-up weekly for four visits.

For skin lesions, a standardized skin surface biopsy was performed for the detection of D. folliculorum in lesion areas. Subjects briefly washed their faces with a bland soap and water and then put on a pair of safety goggles. A drop (about 0.05?ml) of cyanoacrylate glue (Krazy Glue) was applied to one end of a plastic slide (1?×?3 inch plastic slides) and spread out to a uniform thickness using the nozzle of the Krazy Glue bottle. The slide was then pressed against a lesion area causing the glue to spread to a thin film the width of the slide (1 inch) and approximately half its length (1.5 inch). The slide was left in place for 5?min while the cyanoacrylate hardened as it polymerized. Initially a standard surface area of 1?cm had been drawn on the other side of the slide with a waterproof marker; the area of 1?cm was divided into four equal squares in order to make counting of the parasite easier after removal of the slide.¹⁷

For the detection of Demodex in anterior blepharitis, under a slit-lamp biomicroscope three eyelashes from each lower eyelid were epilated with fine forceps. Eyelashes were placed on a glass slide and mounted with a cover slip. Epilated eyelashes and skin samples were clarified with two to three drops of immersion oil and examined microscopically at standard magnifications (×40 to?×?100) as soon as possible (within 2–4?h), as the movement of mites decreases with time and they may even disintegrate.¹⁸ For eyelashes, determination of ?3 living parasites at the root of each eyelash was diagnosed as infestation. The Demodex count was recorded as the total number of mites found in a total of three lashes per eye. For the diagnosis of a skin sample infestation, >5 living parasites in an area 1?cm² was required.¹⁹ Patients were assessed prior to randomization and weekly for 1 month throughout the study.

The outcome measurements were done at the last visit. The primary outcome was a decrease in mite density for each treatment (?5 mites/cm² for skin lesions and <3 living mites/eyelash). Secondary outcomes were clinical improvements in itching, burning, redness, and scaling at the root of the lashes in anterior blepharitis patients, and improvements in erythema, dryness, scaling, roughness, and/or papules/pustules in skin lesions.

Assessment of the outcome samples was done by two unblinded parasitologists and then reviewed by another independent blinded professor of parasitology to avoid bias.

Data entry and analysis were all done using SPSS software version 17 (Chicago, IL, USA). Results were expressed as mean ± standard deviation (SD), or number (%). Comparisons between the mean values were done using the independent sample t-test and Mann–Whitney test. The Chi-square test was used to compare the primary outcome in ivermectin and combined regimens and for comparison between categorical data (number (%)). The 95% confidence interval (95% CI) for the difference between independent proportions was calculated by the Wilson with continuity correction method. A p-value of <0.05 was considered statistically significant.

One hundred twenty eligible patients were enrolled in this study; no patient missed any follow-up visit or discontinued treatment. Sixty patients were allocated to receive ivermectin and 60 to receive the combined therapy.

Baseline characteristics of the patients in each group are summarized in Table 1.

In the cases who received ivermectin alone, there was a gradual reduction in the mean follicle mite count at the first week visit (Table 2). However, rebound elevation in the mite count was evident in the third week in some patients with rosacea and those with anterior blepharitis lesions (Table 2).

In the combined therapy subgroup, the mean counts of Demodex were dramatically reduced in all patients within 1 week (Table 2).

In comparing the efficacy of the two regimens, we demonstrated that the combined therapy was superior in decreasing the mean count of D. folliculorum in all groups (p < 0.05) (Table 2) and in reducing the mite count to a normal level in rosacea (mite density ?5 mites/cm²) (p?<?0.001; 95% CI 0.4–0.9) (Figure 1; Table 3) and in blepharitis (<3 mites/eyelash) (p?=?0.002; 95% CI 0.2–0.8) (Figure 2; Table 3). The two regimens were comparable in terms of the reduction in mite count to a normal level in the acne group (p?=?0.1; 95% CI ?0.04–0.6) (Figure 3; Table 3) and peri-oral dermatitis group (p?=?0.5; 95% CI ?0.1–0.4) (Figure 4; Table 3) (mite density ?5 mites/cm²).

Figure 1

Mite density of rosacea group before treatment and through follow up visits using different regimen therapy.

View Large Image | View Hi-Res Image | Download PowerPoint Slide

Figure 2

Mite density of blepharitis group before treatment and through follow up visits using different regimen therapy.

View Large Image | View Hi-Res Image | Download PowerPoint Slide

Figure 3

Mite density of acne group before treatment and through follow up visits using different regimen therapy.

View Large Image | View Hi-Res Image | Download PowerPoint Slide

Figure 4

Mite density of peri-oral dermatitis group before treatment and through follow up visits using different regimen therapy.

View Large Image | View Hi-Res Image | Download PowerPoint Slide

With regard to clinical improvement, at the last visit for those on the combined therapy regimen, 1.7% of patients showed no clinical improvement, 26.7% showed a marked clinical improvement, and 71.6% showed complete remission, while in those on the ivermectin regimen, 27 patients had a mite count >5 mites/cm², 21.7% of them showed no clinical improvement, 33.3% showed a marked improvement, and 45% showed complete remission.

At the end of the follow-up, one case on the combined therapy regimen had an infestation that continued to be treatment-resistant (the mites were persistent in their lesions) and after histopathological examination of the lesion, the case was diagnosed as lupus miliaris disseminatus faciei (LMDF).