Effects of Nebivolol, Atenolol and Propranolol on Airway β-Adrenergic Responsiveness in Normal Subjects

Pulmonary effects of nebivolol

The pharmacological control of arterial hypertension is a very frequent issue in clinical practice and some critical aspects can arise in particular circumstances and with particular molecules. In the case of hypertensive subjects with respiratory comorbidities, when first introduced, these beta-adrenergic receptor antagonists were described as affecting airway patency as a result of their antagonism against beta(2)-adrenergic receptors within airway muscles. New molecules with a better respiratory tolerability were subsequently designed in order to overcome the narrow therapeutic window of first-generation beta-adrenergic receptor antagonists. Nebivolol is a third-generation beta-adrenergic receptor antagonist with high beta(1)-selective adrenergic receptor antagonism and vasodilating properties that induces a substantial decrease of arterial pressure in hypertensive subjects while preserving their left ventricular function. Respiratory effects of nebivolol have been investigated in animal models, in healthy volunteers and in clinical trials carried out on patients suffering from bronchial asthma and chronic obstructive pulmonary disease (COPD). In contrast to older compounds, nebivolol, which modulates the endogenous production of nitric oxide and affects oxidative cascade, proved clinically well tolerated in terms of respiratory outcomes in this type of subject. Moreover, due to the substantial dissociation between its cardiac and pulmonary activity, nebivolol confirmed a very good safety profile when regularly administered to hypertensive subjects with obstructive respiratory comorbidities.

Nebivolol: pharmacologic profile of an ultraselective, vasodilatory beta1-blocker

Beta-blockers are well-established therapeutic agents in the treatment of hypertension and cardiovascular disease. However, these agents are highly heterogeneous. Beta-blockers differ in their ancillary pharmacologic properties, which are clinically important. Nebivolol is a highly selective beta(1)-adrenergic receptor blocker that induces vasodilation through stimulation of the endothelial nitric oxide/L-arginine pathway. As a racemic mixture of d- and l-enantiomers, nebivolol is highly lipophilic and rapidly absorbed. Nebivolol undergoes extensive hepatic metabolism through the cytochrome P450 2D6 (CYP2D6) system. As a result of genetic polymorphisms, CYP2D6 has variable activity, manifested by extensive and poor metabolizers of nebivolol. Time to maximum concentration is 0.5 to 2 hours, and half-life is 11 hours in extensive metabolizers; these values are about 3 times longer in poor metabolizers. Urinary and fecal excretion of unchanged nebivolol is less than 0.5% of the dose. Nebivolol has a unique hemodynamic profile of reduced systemic vascular resistance and increased left ventricular function. These properties are attributed to its vasodilating action and contrast with the hemodynamic effects of conventional beta-blockers. Nebivolol is thus a novel beta-blocker with several important pharmacologic properties that distinguish it from traditional beta-blockers. These unique properties may confer clinical benefits beyond simple blood pressure lowering.

A comparison of the beta1-selectivity of three beta1-selective beta-blockers

OBJECTIVE

To determine the relative beta1-selectivity of three beta-blockers (nebivolol, bisoprolol and atenolol), administered orally at normal therapeutic doses, by assessing their impact on the beta2-mediated, haemodynamic and biochemical responses to a terbutaline infusion, which decreases serum potassium and increases serum glucose and insulin.

METHODS

Twenty-four healthy volunteers (14 men, 10 women), with no history of respiratory disease, attended on five separate occasions; beta-blockers (nebivolol 5 mg, bisoprolol 10 mg, atenolol 50 and 100 mg) or placebo were supplied in random order. Three baseline blood samples were collected at 65-85 min post-beta-blocker. A 60-min terbutaline infusion was started 90 min after taking the beta-blocker. Blood samples were taken and blood pressure and heart rate recorded at 15 min intervals up to 30-min post-infusion. Blood samples were analysed for serum potassium, glucose and insulin concentrations.

RESULTS

Terbutaline increased heart rate. Pretreatment with nebivolol caused a modest and non-significant reduction in terbutaline-induced tachycardia whilst bisoprolol produced a more marked effect. Atenolol at both 50 and 100 mg doses caused a highly significant reduction in terbutaline-induced tachycardia. All active preparations had a comparable impact on the terbutaline-induced increase in systolic blood pressure, but the drugs had no impact on the changes produced in diastolic blood pressure. After pretreatment with placebo, the terbutaline infusion caused a significant decrease in serum potassium and increases in serum glucose and insulin. Pretreatment with nebivolol had no discernible effect on potassium compared with placebo. In contrast, when compared with either placebo or nebivolol, bisoprolol (P < 0.01) and both doses of atenolol (P < 0.001) significantly attenuated the hypokalaemic effect of terbutaline. Treatment with nebivolol and bisoprolol modestly but significantly reduced the terbutaline-induced increases in glucose (P < 0.05). The blocking effects of both doses of atenolol were highly significant (P < 0.001) when compared with placebo and also significant (P < 0.05 and P < 0.01, respectively) when compared with nebivolol and bisoprolol. A similar pattern of responses with the different beta-blocker treatments was observed for the effects on insulin concentrations during the terbutaline infusion.

CONCLUSION

The beta1-selectivity of three different beta1-blockers has been demonstrated in healthy volunteers using the blocking of biochemical and haemodynamic responses to a beta2 stimulus. Terbutaline alone caused an increase in heart rate, a rise in systolic blood pressure, a fall in serum potassium and a rise in both serum glucose and insulin. In this study, for both haemodynamic and biochemical responses, atenolol 100 mg had the greatest beta2-blocking effect, nebivolol 5 mg the least. Bisoprolol 10 mg and atenolol 50 mg had intermediate effects; bisoprolol was the more beta1-selective of these two.

Beta 1-adrenoceptor selectivity of nebivolol and bisoprolol. A comparison of [3H]CGP 12.177 and [125I]iodocyanopindolol binding studies

There is an ongoing discussion on whether or not high beta(1)-adrenoceptor selectivity of beta-adrenoceptor antagonists may be favorable in the treatment of patients with heart failure. The present study compared the beta(1)-adrenoceptor selectivity of nebivolol and bisoprolol with that of carvedilol in the human myocardium, using a binding assay in conjunction with either the hydrophilic ligand (+/-)-[3H]4-(3-tertiarybutylamino-2-hydroxypropoxy)-benzimidazole-2-on HCl ([3H]CGP 12.177) or the lipophilic ligand [125I]iodocyanopindolol as radiolabeled compound. Measurements were made using membrane preparations obtained from identical nonfailing donor hearts. beta-adrenoceptor density was found to be slightly higher when [125I]iodocyanopindolol was used compared to [3H]CGP 12.177 (256+/-15 and 213+/-18 fmol/mg protein, respectively). When the highly beta(1)-adrenoceptor-selective compound 2-hydroxy-5-(2-(hydroxy-3-(4((1-methyl-4-trifluoromethyl)-1-H-imidazol-2-yl)-phenoxy)-propyl)-aminoethoxyl)-benzamide (CGP 20.712A) and the highly beta(2)-adrenoceptor-selective compound erythro-(+/-)-1-(7-methylindan-4-yloyl)-3-isopropylaminobutan-2-ol HCl (ICI 118.551) were used in competition experiments, a similar proportion of beta(1)-adrenoceptors was seen for [3H]CGP 12.177 (69.3+/-1.6%) and for [125I]iodocyanopindolol (67.0+/-2.1%). K(i)(beta(1)) and K(i)(beta(2)) were obtained in the presence of 50 nM ICI 118.551 and 300 nM CGP 20.712A. The rank order of beta(1)-adrenoceptor selectivity (K(i)(beta(2))/K(i)(beta(1)) ratio) was nebivolol (for [3H]CGP 12.177 46.1 and for [125I]iodocyanopindolol 22.5)>bisoprolol (13.1 and 6.4)>carvedilol (0.65 and 0.41). To investigate whether in vivo metabolized nebivolol retains high beta(1)-adrenoceptor selectivity, serum specimens were collected before and 2 h after oral administration of 5 mg nebivolol. The samples were used for [125I]iodocyanopindolol binding studies with the myocardial membrane preparations. In these samples, the binding of [125I]iodocyanopindolol to beta(1)-adrenoceptors was inhibited by 46.4+/-5.3%, whereas the binding to beta(2)-adrenoceptors was inhibited by 20.5+/-1.1% compared to that of control samples. It is concluded that nebivolol is approximately 3.5 times more beta(1)-adrenoceptor-selective than bisoprolol in the human myocardium. Furthermore, in vivo metabolized nebivolol retains beta(1)-adrenoceptor selectivity.

The pharmacologic treatment of uncomplicated arterial hypertension in patients with airway dysfunction

Because many antihypertensive drugs can affect airway function, the treatment of hypertension in patients with airway dysfunction is complex. For example, the worsening or precipitation of asthma by beta-adrenoceptor antagonists is well-recognized, but beta(1)-adrenoceptor blockers that exert mild beta(2)-agonist effects, and those that modulate the endogenous production of nitric oxide, affect airway function to a lesser extent. Therapy with selective alpha(1)-blockers is not contraindicated in cases of chronic airway obstruction. Conversely, alpha(2)-agonists must not be given to asthmatic subjects because they can adversely affect the bronchi. Calcium channel blockers do not exert severe side effects on the airways. Angiotensin-converting enzyme inhibitors may cause cough and exacerbate or even induce asthma; however, angiotensin II type I (AT(1)) antagonists do not cause cough. 5-Hydroxytryptamine modifiers such as urapidil are a treatment option for patients with chronic airway obstruction. In patients with airway dysfunction, we suggest treatment with thiazide diuretics as the initial drug choice, and calcium channel blockers if the response is poor. In the case of no response, calcium channel blockers alone must be used. However, there is no strict rule because individual patients may respond differently to individual drugs and drug combinations. Consequently, it is important to adopt a flexible approach. For patients who are unresponsive to the aforementioned drugs, AT(1) receptor antagonists, newer beta(1)-adrenoceptor-blocking agents with ancillary properties (eg, celiprolol or nebivolol), and/or vasodilators can be considered.

Comparison of the effects of single oral doses of nebivolol and celiprolol on airways in patients with mild asthma

OBJECTIVE

The respiratory effects of nebivolol, a new selective ss(1)-adrenergic blocking agent, and celiprolol, a ss-blocker possessing strong ss(1)-adrenoceptor antagonist and mild ss(2)-agonist properties, were investigated in 12 patients with mild asthma.

DESIGN

Changes in several spirometric indexes (FVC, FEV(1), and forced expiratory flow rate at 50% of FVC) were measured. The interaction with the bronchodilator effect of the ss(2)-adrenoceptor-selective agonist albuterol also was investigated.

RESULTS

The effect of both nebivolol and celiprolol on FEV(1) was considered to be significant (p < 0.05). The administration of nebivolol and celiprolol, but not of placebo, elicited a decrease in FEV(1): mean maximum difference for nebivolol, -0.272 L (95% confidence interval [CI], -0.402 to -0.142); mean maximum difference for celiprolol, -0.193 L (95% CI, -0.316 to -0.071); mean maximum difference for placebo, -0.0001 L (95% CI, -0.087 to 0.085). The inhalation of albuterol, up to a dose of 800 microg, significantly (p < 0.05) improved FEV(1), but the values after nebivolol and celiprolol administration were lower than the initial values. Both ss-blockers caused equal changes in heart rate, systolic BP, and diastolic BP.

CONCLUSIONS

There were no significant differences between the respiratory actions of the two active drugs.

Pharmacological properties of nebivolol in man

OBJECTIVES

The aims of the present study were to determine (1) the beta 1-blocking potency and (2) the beta 1-adrenoceptor selectivity of nebivolol in man after repeated dosing (7 days) compared with that after a single oral intake and with that after atenolol for 7 days. In addition, it was investigated whether (3) nebivolol has alpha 1-blocking properties which might at least in part explain the vasodilating property of the compound.

METHODS

Twelve healthy subjects were randomized in an open, two-way cross-over study. beta 1-Blocking potency and beta 1-adrenoceptor selectivity of nebivolol 5 mg once daily (o.d.) were compared with those of atenolol at three doses (25, 50 and 100 mg) o.d. Measurements were performed after 1 and 7 days of drug intake. beta 1-Adrenoceptor potency was assessed by the percentage decrease in exercise-induced tachycardia (delta EIT) during beta-blockade. beta 1-Selectivity of nebivolol and atenolol were investigated using the heart rate response to isoprenaline at equipotent beta 1-blocking dosages of both drugs. alpha 1-Blockade of nebivolol was measured using the phenylephrine dose-response test.

RESULTS

delta EIT after a single oral dose of nebivolol 5 mg (10%) was significantly smaller than after nebivolol 5 mg o.d. for 7 days (15%). After 1 week of treatment no difference was seen in delta EIT between nebivolol 5 mg o.d. and atenolol 25 mg o.d. (16%). At these dosages the suppression in isoprenaline-induced tachycardia by both drugs did not differ (CD20 ratio 1.7). In contrast to atenolol 25 mg, after 1 week of nebivolol 5 mg o.d., blood pressure decreased. This decrease averaged 10% and-like in a study with hypertensive patients-was similar with that after atenolol 100 mg o.d. None of the phenylephrine test parameters changed from pre-study values after nebivolol.

CONCLUSIONS

beta 1-Blockade of nebivolol 5 mg is larger after repeated dosing than after a single oral intake. After once daily repeated dosing nebivolol 5 mg and atenolol 25 mg are equipotent in beta 1-antagonism. No difference in beta 1-selectivity is observed between the two drugs. Nebivolol has no additional alpha 1-blocking property, which may at least in part explain its vasodilating effect.