Dichloroisoprenaline also known as dichlorosisoproterenol, was the first beta blocker

Beta blocker

Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...

 ever to be developed. It is non-selective for the β₁-adrenergic and β₂-adrenergic receptors. DCI has low potency

Potency

Potency may refer to:* Potency , a measure of the activity of a drug in a biological system* Virility* Potency is a measure of the differentiation potential of stem cells...

 and acts as a partial agonist

Partial agonist

Partial agonists bind and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist...

/antagonist

Receptor antagonist

A receptor antagonist is a type of receptor ligand or drug that does not provoke a biological response itself upon binding to a receptor, but blocks or dampens agonist-mediated responses...

 at these receptor

Receptor (biochemistry)

In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...

s.

Although DCI was of no clinical value itself, further developments from DCI eventually led to the development of the clinical candidate pronethalol

Pronethalol

Pronethalol was an early non-selective beta blocker clinical candidate. It was never used clinically due to carcinogenicity in mice, which was thought to result from formation of a carcinogenic naphthalene epoxide metabolite....

 (withdrawn due to carcinogenicity) and subsequently propranolol (the first clinically-successful beta blocker).

Dichloroisoprenaline is a racemic mixture of enantiomers.