α-agonists in glaucoma

α-agonists in glaucoma

α-adrenoreceptor agonists lower the intraocular pressure by two mechanisms: They reduce aqueous humour production. Apraclonidine directly reduces aqueous humour production by stimulating the α2 receptor in the ciliary body. This drug also reduces ciliary blood flow

by activation of the α1receptor. This derivative of clonidine cannot pass the blood-brain-barrier and thus causes fewer side effects on blood pressure. They enhance the outflow of aqueous humour via the uveoscleral outflow (α2receptors).

α-agonists epinephrine and its pro-drug dipivefrine are non-selective. Epinephrine is poorly available at the site of action, while dipivefrine is highly lipophilic and can reach the ciliary body, where is it converted into epinephrine.