(-)-Propranolol is a small molecule β-adrenergic receptor antagonist and the active isomer of (±)-Propranolol preparations. (-)-Propranolol blocks the binding of epinephrine, norepinephrine, and other endogenous catecholamines to the β-adrenergic receptor, impeding increases in cardiac flow velocity and general stimulation of the sympathetic nervous system signaled by the association of these molecules to the β-adrenergic receptor. In addition to blockade of agonist binding, antagonism of the β-adrenergic receptor by (-)-Propranolol produces negative chronotropic and inotropic action, effectively dampening the force and rate of cardiac contraction. These negative chronotropic and inotropic effects correlate to a demonstrated suppression of adrenaline-induced cardiac arrhythmia by (-)-Propranolol. Suppression of β-adrenergic receptor activation by (-)-Propranolol has been widely exploited in counteracting situations sensitive to heightened cardiac activity including hypertension, angina pectoris, and cardiac ischemia.

Carazolol is a beta1/beta2 adrenoreceptor blocking agent. Activity and safety of the drug were evaluated in clinical trials that were conducted in healthy subjects and in patients suffering from either chronic bronchitis or asthma. The drug, however, was not developed for human use. Instead, carazolol is used in to reduce stress in animals during transportation. In veterinary medicine, carazolol is given by intramuscular injection to pigs is indicated in stress-inducing situations. In cattle, carazolol is intended to be used for the prevention of shipment stress caused by transportation and formation of new herds.

Dopexamine hydrochloride is a synthetic catecholamine, structurally related to dopamine, with marked intrinsic agonist activity at beta 2-adrenoceptors, lesser agonist activity at dopamine DA1- and DA2-receptors and beta 1-adrenoceptors, and an inhibitory action on the neuronal catecholamine uptake mechanism. The drug is administered by intravenous infusion, and is characterized by a rapid onset and short duration of action. Dopexamine is being tested as a treatment for heart failure and sepsis.

Bucumolol is a beta-adrenergic antagonist. It can be used in the treatment of myocardial ischemia and hypertension.

Trimetoquinol hydrochloride dilates bronchial muscle selectively by stimulating Beta 2-receptors. It is used for the relief of bronchoconstriction associated with bronchitis, asthmatic bronchitis and bronchial asthma. Since the concurrent use of the drug with catecholamines such as Epinephrine and Isoproterenol may induce arrythmia or cardiac arrest in some cases, concurrent use is not recommended. Adverse reactions : Palpitation may occur occasionally, and alteration of blood pressure and precordial pain may appear rarely; headache may occur occasionally; tremor, dizziness, feverish sensation may also be encountered in a rare incidence; occasionally, nausea and anorexia may appear.

Zinterol (MJ-9184-1) is an beta-adregenrgic agonist demostrated activity toward beta1-3 receptors. Oral zinterol caused a fast-appearing and long-lasting bronchodilator effect in patients with with stable chronic obstructive lung disease, however it seems development of zinterol was discontitued.

Clorprenaline is a β2-adrenergic receptor agonist. As a bronchodilator it has been used for the treatment of bronchial asthma, bronchitis and other respiratory diseases. It is a potential new lean meat-boosting feed additive because it can promote animal muscular mass growth and decrease fat accumulation.

Dilevalol, the RR-stereoisomer of labetalol, is a non-cardioselective β-adrenoceptor antagonist with substantial partial β2-agonist and negligible α1-blocking activity. Reduction in blood pressure during dilevalol administration is associated with peripheral vasodilatation, and heart rate remains essentially unchanged. Following oral administration, dilevalol is completely absorbed. Once-daily administration is possible, due to a long elimination half-life. In vitro and in vivo animal studies and results obtained in humans reveal that dilevalol is a nonselective blocker of β1- and β2-adrenoceptors, with a similar potency to propranolol, but has negligible antagonistic activity at α1-receptors. Dilevalol, the R,R′ stereoisomer, makes up 25% of racemic labetalol, the drug, approved by FDA for the treatment of hypertension. The relaxing potency of dilevalol was approximately 4.7 times more potent than that of labetalol. Dilevalol markedly reduced the diastolic blood pressure with only a slight increase of heart rate In pithed rats, while isoproterenol and pindolol caused moderate to marked positive chronotropic effects in proportion to their hypotensive effects. These results suggest that dilevalol has more potent ISA than labetalol. In contrast to labetalol, dilevalol possesses little, if any, alpha-adrenergic blocking activity. The compound is 3 to 10 times less potent than labetalol at α1-adrenergic receptors under a variety of experimental conditions. Moreover, it is 300- to 1000-fold less potent at alpha1-adrenergic receptors compared with β1-adrenergic receptors. The pA2 values for dilevalol as an α antagonist range from 5.9 to 6.4. Because maximal plasma concentrations of the drug after administration of a 400-mg dose are approximately 0.5 pmol, it is doubtful that alpha blockade is involved in the antihypertensive response to dilevalol in humans.

Tulobuterol is a long-acting beta2-adrenergic receptor agonist. Tulobuterol has almost no effects on blood pressure and heart rate and is highly selective for the tracheal muscle. It is indicated to improve symptoms such as respiratory distress caused by airway obstruction of bronchial asthma, bronchitis, chronic obstructive pulmonary disease (COPD) and emphysema. Serious side effects detected were: tremor, palpitations and serum potassium level decrease.

Ractopamine hydrochloride, a beta-adrenoceptor agonist, is a phenethanolamine salt approved for use as a feed additive. Recently published studies indicate that the RR-isomer (butopamine) is the stereoisomer with the most activity at the beta-adrenoceptor. Butopamine was shown to be a non-selective ligand at the beta1 and beta2-adrenoceptors, but signal transduction is more efficiently coupled through the b2-adrenoceptor than the beta1 adrenoceptor. Therefore, the RR-isomer of ractopamine is considered to be a full agonist at the beta2-adrenoceptor and a partial agonist at the beta1¬adrenoceptor. These results are consistent with the pharmacological characterization of racemic ractopamine in isolated cardiac (atria) and smooth muscle (costo-uterine, vas deferens, trachea), which shows a maximal response at beta2- and a submaximal response at beta1¬adrenoceptors when compared with the full beta1 and beta2-adrenoceptor agonist isoproterenol. Butopamine is chemically similar to dobutamine but, unlike dobutamine, it is not a catecholamine. Butopamine induces a positive inotropic response in patients with congestive heart failure but for equal increments in cardiac output, butopamine increases heart rate more than dobutamine. Butopamine inproved cardiac performance in patients with ventricular dysfunction and congestive heart failure. Butopamine was prepared by Tuttle et al (unpublished data) and has a structure similar to dobutamine. This compound is refractory to the action of catechol-O-methyl transferase and thus it is orally active and has a longlasting action. Clinical findings in acute heart failure cases have been reported by Thompson et al. Intravenous administration produced an increase in the cardiac index and heart rate and shortening of systolic time intervals. A few patients experienced ventricular ectopy, especially with the higher doses used. No data pertaining to oral administration are available.