Isoproterenol

Isoproterenol hydrochloride or isoprenaline (Medihaler-Iso®) is a sympathomimetic beta adrenergic receptor agonist medication, used as an inhaled aerosol to treat asthma. Although it activates all beta adrenergic receptors, it works in a similar fashion to the more selective beta2-adrenergic receptor agonists e.g. salbutamol, by relaxing the airways to increase airflow.

It is also supplied in ampules under the brand name Isuprel® for injection and in sublingual pill form for treatment of asthma, chronic bronchitis and emphysema.

It is structurally similar to epinephrine but acts for the most part on beta receptors.

Used with caution, it can also be used to treat torsades de pointes, in conjunction with overdrive pacing and magnesium.

Pharmacological details
Isoprenaline is a synthetic derivative of noradrenaline that is not found in the body. It is also known as Isoproterenol.

It is a β1 and β2-adrenoceptor agonist which was commonly used to treat asthma before the more widespread use of salbutamol, which has more selective effects on the airways. Its route of administration is either intravaneous, oral, intranasal, subcutaneous or intramuscular depending on use.

Isoprenaline is a sympathomimetic agent and is a non-selective β-adrenoceptor agonist. It has unwanted side effects which include tachycardia and dysrhythmias that result from activation of β1 receptors in the heart. The plasma half life for isoprenaline is about 2 hours.

Stimulation of β1-adrenoceptors also leads to enhancing of phase 4 depolarisation in SA nodal cells, increasing the pacemaker potential (leading to increased frequency of contraction-chronotropy)

Warnings and Contraindications
Isoproterenol should not be administered to patients with myocardial ischaemia.