Oral antibiotics for chronic blepharitis

Background Posterior blepharitis is common and causes ocular surface and lid damage as well as discomfort. It affects 37% to 47% of all ophthalmology patients; its incidence increasing with age. It is a multifactorial disease associated with multiple other pathologies, such as rosacea, meibomianitis, and infections. Treatment usually focuses on reliefing the symptoms by using artificial tears, lid scrubs, and warm compresses. The condition may be notoriously difficult to manage adequately once it becomes chronic. One such management approach for chronic blepharitis is the use of oral antibiotics for both their antibacterial as well as anti-inflammatory properties. There are currently no guidelines regarding the use of oral antibiotics, including antibiotic type, dosage, and treatment duration, for the treatment of chronic blepharitis. Objectives To assess the benefits and harms of oral antibiotic use for people with chronic blepharitis. Search methods We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2020, Issue 8); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature Database (LILACS); ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 29 August 2020. Selection criteria We included randomized controlled trials (RCTs) comparing oral antibiotics with placebo in adult participants with chronic blepharitis (including staphylococcal, seborrhoeic, or Meibomian Gland Dysfunction (MGD)). Data collection and analysis We used standard Cochrane methodology and graded the certainty of the body of evidence for six outcomes using the GRADE classification. Main results We included two studies with 220 participants (numbers of eyes unclear). One parallel-group RCT comparing oral doxycycline (40 mg once a day) with placebo enrolled 70 participants with blepharitis and facial rosacea in the USA. Follow-up duration was three months. One three-arm RCT conducted in South Korea investigated the effect of high-dose (200 mg twice a day) and low-dose (20 mg twice a day) doxycycline versus placebo after one month of study medication. It enrolled 50 participants with chronic MGD in each study arm (i.e. 150 participants enrolled in total). The two studies did not evaluate the same outcome measurements, which precluded any meta-analysis. The evidence for the effect of oral antibiotics on subjective improvement in symptoms was very uncertain. One study suggested that there was little to no effect of oral doxycycline on subjective symptoms based on the Ocular Surface Disease Index (OSDI) scores ranging from 0 to 100 (higher score indicates worse condition) (mean difference (MD) 3.55, 95% confidence interval (CI) -4.61 to 11.71; n = 70) and bulbar conjunctival hyperemia ranging from 0 (clear) to 4 (severe) (MD -0.01, 95% CI -0.38 to 0.36; n = 70) at 12 weeks. The three-arm RCT showed that oral doxycycline may slightly improve number of symptoms (MD -0.56, 95% CI -0.95 to -0.17; n = 93 (high-dose doxycycline versus placebo); MD -0.48, 95% CI -0.86 to -0.10; n = 93 (low-dose doxycycline versus placebo)) and proportion of participants with symptom improvement (risk ratio (RR) 6.13, 95% CI 2.61 to 14.42; n = 93 (high-dose doxycycline versus placebo); RR 6.54, 95% CI 2.79 to 15.30; n = 93 (low-dose doxycycline versus placebo)) at one month, but the evidence is very uncertain. We judged the certainty of evidence for subjective symptoms as very low. One study evaluated aqueous tear production by Schirmer's test (mm/5 min) (higher score indicates better condition) and tear film stability by measuring tear film break-up time (TBUT) in seconds (higher score indicates better condition) at one month. We found very low certainty evidence that oral doxycycline may improve these clinical signs. The estimated MD in Schirmer's test score after one month of treatment was 4.09 mm (95% CI 2.38 to 5.80; n = 93) in the high-dose doxycycline group versus the placebo group and 3.76 mm (95% CI 1.85 to 5.67; n = 93) in the low-dose doxycycline group versus the placebo group. The estimated MD in TBUT after one month was 1.58 seconds (95% CI 0.57 to 2.59; n = 93) when comparing the high-dose doxycycline group with the placebo group, and 1.70 seconds (95% CI 0.96 to 2.44; n = 93) when comparing the low-dose doxycycline group with the placebo group. Although there was a noted improvement in these scores, their clinical importance remains uncertain. One study suggested that oral doxycycline may increase the incidence of serious side effects: 18 (39%) participants in the high-dose doxycycline group, 8 (17%) in the low-dose doxycycline group, and 3 (6%) out of 47 participants in the placebo group experienced serious side effects (RR 6.13, 95% CI 1.94 to 19.41; n = 93 (high-dose doxycycline versus placebo); RR 2.72, 95% CI 0.77 to 9.64; n = 93 (low-dose doxycycline versus placebo)). Additionally, one study reported that one case of migraine headache and five cases of headache were observed in the oral doxycycline group, and one case of non-Hodgkin's lymphoma was observed in the placebo group. We judged the certainty of evidence for adverse events as very low. Authors' conclusions There was insufficient evidence to draw any meaningful conclusions on the use of oral antibiotics for chronic blepharitis. Very low certainty evidence suggests that oral antibiotics may improve clinical signs, but may cause more adverse events. The evidence for the effect of oral antibiotics on subjective symptoms is very uncertain. Further trials are needed to provide high quality evidence on the use of oral antibiotics in the treatment of chronic blepharitis.