Arotinolol

The stereospecificity of arotinolol is very important for its pharmacokinetic characteristics. Arotinolol is highly bound to serum proteins reaching a ratio of the original dose of 95.3% in the form of the R-enantiomer and 84.5% of the S-enantiomer. The presented stereospecificity is thought to be related to the α1-acid glycoprotein.

Preclinical studies showed a lack of intrinsic sympathomimetic activities or membrane-establishing properties. It is confirmed that arotinolol presents vasorelaxant activity. This characteristic is also proved to be mainly mediated by its α1-blocking property. In preclinical hypertension trials, there is a specific acute bradycardiac and antihypertensive activity with a pronounced reduction in heart rate. Some reports indicate a delayed development of hypertension when arotinolol is administered daily. Arotinolol has a dose-dependent decrease in cardiac contractility and coronary blood flow as well as an increase in total peripheral resistance. The effects of arotinolol have been confirmed in clinical trials where this drug was able to decrease cardiac index and thus, blood pressure.

Arotinolol binds to the β1-, β2- and α1- adrenergic receptor sites with a very high affinity. Radioligand studies have shown that arotinolol presents a higher affinity to the β-receptor compared to the α-receptor. The elucidated mechanism of action seems to be the result of a reduction in the cardiac output via the β-blockade and an additional inhibition of the counter-regulatory increase in peripheral resistance mediated by the α-blockade.