Therapeutic Efficacy of Metipranolol Eye Drops 0.3% Versus Timolol Eye Drops 0.25%
Since the introduction of β-sympathicolytics in the treatment of elevated intraocular pressure a great number of studies on β-receptor blocking agents dealing with the dynamics of the aqueous humour have been conducted. Ever since the pressure reducing effect was first described in 1970 , timolol represents the most widely used β-blocking agent. Timolol is to be classified along with the noncardioselective β-blocking agents, i. e. responsible for the blockade both at the cardial β-1-receptors and at the extra-cardial β-2-receptors of the bronchi and vessels. The newly developed β-blocking agent metipranolol demonstrates slight β-blocking equipotent doses to inhibit isoproterinol tachycardia compared with propranolol. It exhibits very slight sympathomimetic properties and, measured by the elevation of the fibrillation threshold in electrically stimulated rabbits hearts , it shows extremely slight membrane-stabilizing properties. The slight β-stimulating property (intrinsic sympathicomimetic activity) both of metipranolol and timolol as well as their slight cardioselectivity already indicate that both drugs are contraindicated in patients with obstructive airways diseases. Relevant studies on the action of non-cardioselective β-blocking agents with and without this effect on the airway resistance  and in patients with small airways disease  have already been presented. A first clinical study on the action of metipranolol in glaucomatous eyes was published in 1982 . On the basis of the comparison with timolol with regard to maximum reductions in intraocular pressure after single medication with mean value and calculation of range of diffusion, the authors concluded that the action of metipranolol and timolol on intraocular pressure in glaucoma patients is about equal. Studies are also available on the topical anaesthetising effect of metipranolol on corneal sensitivity .
KeywordsIntraocular Pressure Obstructive Airway Disease Elevated Intraocular Pressure Small Airway Disease Heart Frequency
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