Metoprolol

Originator

Betaloc,Astra,UK,1975

The Uses of Metoprolol

Metoprolol is used in moderate hypertension, serious conditions of myocardial infarction, for preventing death of cardiovascular tissue, in angina, tachycardia, extrasystole, and for secondary prophylaxis after a heart attack.

The Uses of Metoprolol

Metoprolol is a β-adrenergic blocking antihypertensive and antianginal agent; to treat raised blood pressure; to prevent attacks of angina (pain from an inadequate oxygen supply to the heart); after a heart attack to prevent further damage to the heart muscle; treatment of some disturbances of heart rhythm; used to help prevent attacks of migraine; in ophthalmic preparations; treatment of myocardial infarcts.

The Uses of Metoprolol

Antiadrenergic (β-receptor).

Definition

ChEBI: Metoprolol is a propanolamine that is 1-(propan-2-ylamino)propan-2-ol substituted by a 4-(2-methoxyethyl)phenoxy group at position 1. It has a role as a beta-adrenergic antagonist, an antihypertensive agent, a xenobiotic, an environmental contaminant and a geroprotector. It is a propanolamine, an aromatic ether, a secondary alcohol and a secondary amino compound.

Manufacturing Process

The starting material 1,2-epoxy-3-[p-(β-methoxyethyl)phenoxy]-propane was obtained from p-(β-methoxyethyl)-phenol which was reacted with epichlorohydrin whereafter the reaction product was distilled at 118°C to 128°C at a pressure of 0.35mm Hg.
1,2-Epoxy-3-[p-(β-methoxyethyl)-phenoxy]-propane (16.7g) was dissolved in 50 ml isopropanol and mixed with 20 ml isopropylamine. The mixture was heated in an autoclave on boiling water-bath overnight, whereafter it was evaporated and the remainder dissolved in 2 N HCI. The solution was extracted first with ether and thereafter with methylene chloride. After evaporating the methylene chloride phase, the hydrochloride of 1- isopropylamino-3-[p(β-methoxyethyl)-phenoxy] -propanol-2 was obtained which, after recrystallization from ethyl acetate, weighed 10.4 g. Melting point 83°C. Equivalent weight: found 304.0, calculated 303.8.
The hydrochloride is then converted to the tartrate.

brand name

Lopressor (Novartis).

Therapeutic Function

Beta-adrenergic blocker

Mechanism of action

Unlike propranolol, which blocks both β1 and β2-adrenoreceptors, metroprolol exhibits cardioselective action, i.e. in therapeutic doses, it blocks β1-adrenoreceptors with insignificant effects on β2-adrenoreceptors.

Synthesis

Metoprolol, 1-(iso-propylamino)-3-[4??(2-methoxyethyl)phenoxy]-2- propanol (12.1.5), is synthesized by reacting 4-(2-methoxyethyl)phenol with epichlorhydride in the presence of a base, isolating 1,2-epoxy-3-[4??(2-methoxyethyl)phenoxy] propane (12.1.4), the subsequent reaction of which, analogous to that described before, with iso-propylamine, gives an opening of the epoxide ring and leads to the formation of metoprolol (12.1.5) [7,8].

Metabolism

The pharmacokinetic profile of metoprolol (Lopressor) is similar to that of propranolol. Metoprolol is readily and rapidly absorbed after oral administration and is subject to a significant amount of first-pass metabolism by the liver. Curiously, the duration of metoprolol’s action is longer than one would predict from its plasma half-life, which ranges from 0.5 to 2.5 hours. The degree of binding of metoprolol to plasma proteins is modest (10%). The extensive distribution of metoprolol to the lungs and kidney is typical of a moderately lipophilic drug. Metoprolol undergoes considerable metabolism;only 3 to 10% of an administered dose is recovered as unchanged drug.The metabolites are essentially inactive as -receptor blocking agents and are eliminated primarily by renal excretion. Small amounts of the drug are present in the feces.