Metipranolol blocks beta1 and beta2 (non-selective) adrenergic receptors. It does not have significant intrinsic sympathomimetic activity, and has only weak local anesthetic (membrane-stabilizing) and myocardial depressant activity.
Orally administered beta-adrenergic blocking agents reduce cardiac output in both healthy subjects and patients with heart disease. In patients with severe impairment of myocardial function, beta-adrenergic receptor antagonists may inhibit the sympathetic stimulatory effect necessary to maintain adequate cardiac output.
Beta-adrenergic receptor blockade in the bronchi and bronchioles may result in significantly increased airway resistance from unopposed parasympathetic activity. Such an effect is potentially dangerous in patients with asthma or other bronchospastic conditions (see CONTRAINDICATIONS and WARNINGS).
OptiPranolol Ophthalmic Solution, when applied topically in the eye, has the action of reducing elevated as well as normal intraocular pressure (IOP), whether or not accompanied by glaucoma. Elevated intraocular pressure is a major risk factor in the pathogenesis of glaucomatous visual field loss.
The higher the level of intraocular pressure, the greater the likelihood of glaucomatous visual field loss and optic nerve damage.
The primary mechanism of the ocular hypotensive action of metipranolol is most likely due to a reduction in aqueous humor production. A slight increase in outflow may be an additional mechanism. OptiPranolol Ophthalmic Solution reduces IOP with little or no effect on pupil size or accommodation.
In controlled studies of patients with intraocular pressure greater than 24 mmHg at baseline, OptiPranolol Ophthalmic Solution reduced the average intraocular pressure approximately 20-26%.
The onset of action of OptiPranolol Ophthalmic Solution, as measured by a reduction in intraocular pressure, occurs within 30 minutes after a single administration. The maximum effect occurs at about 2 hours. A reduction in intraocular pressure can be demonstrated 24 hours after a single dose.
Clinical studies in patients with glaucoma treated for up to two years indicate that an intraocular pressure lowering effect is maintained.
In rabbits administered metipranolol in one eye at 2 to 4 fold increased concentrations, multi-focal interstitial nephritis was observed in male animals, and lympho-hystiocytic and heterophilic interstitial pneumonia was observed in female animals. The clinical relevance of these findings is unknown.