Unoprostone (isopropyl unoprostone) is a docosanoid compound which is related to a metabolite of prostaglandin (PG)F2 alpha. Unoprostone has oculo-hypotensive effects. The drug is thought to lower intraocular pressure (IOP) by increasing aqueous humour outflow. Aqueous humour production remains unaffected. Marked reductions in IOP have been demonstrated in healthy volunteers and patients with glaucoma or ocular hypertension after instillation of unoprostone 0.12%. Unoprostone 0.12% appears to have similar efficacy to timolol 0.5% in patients with primary open-angle glaucoma or ocular hypertension. In phase II and III clinical studies, adverse events observed with unoprostone were predominantly local; systemic effects occurred less frequently.