Isoprenaline (INN) or isoproterenol (USAN, trade names Medihaler-Iso and Isuprel) is a medication used for the treatment of bradycardia (slow heart rate), heart block, and rarely for asthma. It is a non-selective beta-adrenergic agonist and structurally similar to adrenaline.

Its primary use is for bradycardia or heart block. By activating β₁-receptors on the heart, it induces positive chronotropic, dromotropic, and inotropic effects.

It can be used as an inhaled aerosol to treat asthma, although this is currently a rare treatment. Although it activates all beta adrenergic receptors, it works in a similar fashion to the more selective β₂-adrenergic 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.

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