Isoproterenol

Absorption

Data regarding absorption kinetics of isoprenaline are not readily available.

Toxicity

Patients experiencing an overdose may present with tachycardia, arrhythmias, palpitations, angina, hypotension, or hypertension. Overdose should be treated by reducing or stopping administration of isoprenaline and monitoring blood pressure, pulse, respiration, and ECG.
In rats, the LD50 is 2221 mg/kg orally, 128 mg/kg intraperitoneally, and 600 mg/kg subcutaneously. In mice, the LD50 is 1260 orally and 450 mg/kg intraperitoneally.

Description

Isoproterenol is a representative of the sympathomimetic drugs with high selectivity to β- adrenoreceptors. As was already noted, the addition to compounds of a bulky iso-propyl or tert-butyl group at the nitrogen atom of the β-phenylethylamino skeleton is associated with higher affinity to β-adrenergic receptive regions than to α-adrenergic. Isoproterenol is devoid of significant α-adrenergic agonistic action. Activation of β1-adrenergic receptors in the heart increases positive chronotropic and ionotropic action. Peripheral vascular resistance is increased by the widening of blood vessels, primarily in skeletal muscle, but also in renal and mesenteric blood circulation, which is caused by the β2-adrenergic system.

Originator

Isonorin,Smith, Miller and Patch,US,1949

The Uses of Isoproterenol

Isoproterenol is used in bronchospasms, asthma, cardiac block, and shock.

The Uses of Isoproterenol

Bronchodilator.

The Uses of Isoproterenol

Isoprenaline is a potent β-agonist primarily acting at the β1-receptor. It is mainly used for the temporary emergency treatment of bradyarrhythmias. β2 effects lead to broncho- and vasodilatation, with a decrease in SVR. Isoprenaline is only available in the UK via specialist importing companies. It is administered by i.v. infusion at a dose range of 0.5–20 μg min–1.

Background

Isoprenaline is a non-selective beta adrenergic receptor agonist indicated to treat heart block, Adams-Stokes attacks, bronchospasm in anesthesia, cadiac arrest, hypovolemic shocks, septic shock, hypoperfusion, congestive hear failure, and cardiogenic shock.
Isoprenaline research in the 1940s found that this isopropyl analog of epinephrine dilated the bronchi, as well as raising the heart rate and cardiac output, without vasoconstriction. The US patent from 1943 states that this compound had a wider therapeutic index and a stronger action than adrenaline.
Isoprenaline was granted FDA approval on 19 February 1948.

Indications

Isoprenaline is indicated to treat mild or transient episodes of heart block not requiring electric shock or pacemakers, serious episodes of heart block and Adams-Stokes attacks not caused by ventricular tachycardia or fibrillation, and bronchospasm during anesthesia. Isoprenaline is also indicated for cases of cardiac arrest until preferable treatments like electric shock and pacemakers are available. Isoprenaline is also indicated as an adjunct therapy to fluid and electrolyte replacement therapy in hypovolemic shock, septic shock, hypoperfusion, congestive heart failure, and cardiogenic shock.

Definition

ChEBI: A secondary amino compound that is noradrenaline in which one of the hydrogens attached to the nitrogen is replaced by an isopropyl group. A sympathomimetic acting almost exclusively on beta-adrenergic receptors, it is used (mainly as the hy rochloride salt) as a bronghodilator and heart stimulant for the management of a variety of cardiac disorders.

Indications

Isoproterenol is administered almost exclusively by inhalation from metered-dose inhalers or from nebulizers. The response to inhaled isoproterenol and other inhaled adrenomimetics is instantaneous. The action of isoproterenol is short-lived, although an objective measurement of pulmonary function has shown an effective duration of up to 3 hours. When it is administered by inhalation, the cardiac effects of isoproterenol are relatively mild, although in some cases a substantial increase in heart rate occurs.

Manufacturing Process

As described in US Patent 2,308,232, 100 g 3,4-dihydroxy-ω- chloroacetophenone, 200 cc ethyl alcohol and 200 cc of about 50% aqueous isopropylamine solution are boiled during 3 hours on the water bath with the use of a reflux condenser, whereupon neutralizing with diluted sulfuric acid is carried out and the sulfate, obtained upon cooling, from alcohol of 50% is recrystallized; its MP is 245°C.
21 g 3,4-dihydroxy-ω-isopropylaminoacetophenone sulfate are hydrogenated with 50 cc methyl alcohol and 50 cc water, 0.5 g carbon and 3 cc palladium chloride solution of 2%. After 2 hours the hydrogen absorption comes to a standstill, after the theoretical quantity of hydrogen has been absorbed. After concentrating, the isopropylaminomethyl-(3,4-dihydroxyphenyl)carbinolsulfate crystallizes out. It has a MP of 180°C after refining.

brand name

Medihaler-ISO (3M Pharmaceuticals);Aerolone;Aerotrol;Afdosa;Aldo asma;Aleudrina;Anthastmin;Asmadren;Asmastop;Atom-asma;Dey-dose;Dispos-a-med;Duo-autohaler;Duo-medihaler;Dyspnoesan;Erydin;Frenal composium;Imuprel;Ingelan;Intal compositum;Iso-autohaler;Isonorin;Isoprel-neomistometer;Isoprop;Isorenin;Katwilon n;Lenoprel;Luf-iso;Medihaler-duo;Meterdos-iso;Neo epinine;Nephenalin;Norisodrin aerotol;Norisodrin with calcium idodide;Norosodrine;Older;Orotenol;Prenomiser;Propynalin;Protenol;Sedantosol;Sooner.

Therapeutic Function

Bronchodilator

World Health Organization (WHO)

Isoprenaline, a beta-adrenoreceptor agonist, was introduced in 1949 as treatment for a number of cardiac disorders and as a bronchial dilator for the symptomatic treatment of asthma. There is evidence that regular inhalation of bronchodilator drugs is associated, in some cases with exacerbation of the disease and with increased fatality rates. The underlying causes are disputed, but an increasing body of opinion now advocates regular maintenance therapy with inhaled, corticosteroids coupled with supplementary use as required of bronchial drugs to suppress exacerbations.

General Description

Isoproterenol is a nonselective and prototypical -agonist ( β2/ β1=1). After oral administration,the absorption of ISO is rather erratic and undependable.The principal reason for its poor absorption characteristicsand relatively short DOA is its facile metabolism by sulfateand glucuronide conjugation of the phenolic OH groupsand O-methylation by COMT. Because it is a catechol, it issensitive to light and air. Aqueous solutions become pinkon standing. Unlike E and NE, ISO does not appear to undergo oxidative deamination by MAO. The drug hasDOA of 1 to 3 hours after inhalation.

Pharmacokinetics

Isoprenaline is a non-selective beta adrenergic receptor agonist used in a number of indications for the heart, as well as bronchospasm in anesthesia. Isoprenaline has a short duration of action as it is rapidly cleared, and a wide therapeutic index. Patients should be counselled regarding the risks of isoprenaline in the treatment of cardiogenic shock following myocardial infarction, paradoxical worsening of heart block, or precipitation of Adams-Stokes attacks.

Clinical Use

The cardiac stimulation caused by its 1-activity andits lack of oral activity have led to its diminished use infavor of more selective -agonists. The problems have beenovercome at least partially by the design and developmentof several noncatechol selective 2-agonists. These agentsrelax smooth muscle of the bronchi, uterus, and skeletalmuscle vascular supply. They find their primary use as bronchodilatorsin the treatment of acute and chronic bronchialasthma and other obstructive pulmonary diseases.

Clinical Use

Isoproterenol is used principally by inhalation for the management of bronchospasm. It is also used intravenously for asthma and as a stimulant in cardiac arrest.

Safety Profile

Poison by ingestion, subcutaneous, intravenous, and intraperitoneal routes. An experimental teratogen. Other experimental reproductive effects. Human systemic effects by intramuscular route: increased pulse and cardac rate. A bronchodilator. Mutation data reported. When heated to decomposition it emits toxic fumes of NOx

Synthesis

Isoproterenol, 1-(3,4-dihydroxyphenyl)-2-iso-propylaminoethanol (11.1.8), is synthesized by an analogous scheme of making epinephrine. Interaction of |?-chloro-3,4- dihydroxyacetophenone (chloroacetylpyrocatechol) with isopropylamine gives |?-isopropylamino-3,4-dihydroxyacetophenone (11.1.7), reduction of the carbonyl group of which by hydrogen using a palladium on carbon catalyst gives isoproterenol (11.1.8) [11,12].

Metabolism

Isoprenaline is predominantly metabolized to glucuronide conjugates. Isoprenaline can also be O-methylated by catechol O-methyltransferase to the metabolite 3-O-methylisoprenaline, which can also be further glucuronidated.