A US pilot study has shown that low-dose doxycycline, an antibiotic with anti-inflammatory characteristics used to treat bacterial infections, meibomian gland dysfunction and rosacea, may be a useful adjunct therapy for intraocular pressure (IOP) reduction.

In a poster presented at the AAO 2022 conference, researchers from the Illinois College of Optometry reported that mild and moderate glaucoma patients with ocular surface disease were treated with daily 50mg doxycycline hyclate for 90 days. The patients maintained their topical IOP-lowering drops at the same level throughout the study while their IOP was measured at baseline, 30, 90 and 180 days. Mean baseline IOP was 16.0 mmHg ± 3.58. At one month there was an 8.31% reduction in IOP; at three months, IOP was down 15.63% from baseline; while at six months (90 days after discontinuing doxycycline), IOP was only 4.38% lower than baseline and 11.76% higher when compared to mean IOP at three months (p=0.006).

Though they acknowledged they did not understand the mechanism for why low-dose doxycycline lowered IOP, the researchers hypothesised doxycycline’s anti-inflammatory effect may reduce trabecular meshwork inflammation and thus outflow resistance. “Because our initial cohort demonstrated a clinical and statistically significant IOP reduction, we plan to continue the study with the goal of enrolling 30-plus patients,” study co-author Dr Dominick Opitz told Healio.