Antagonistic effects of bisoprolol on several beta-adrenoceptor-mediated actions in anaesthetized cats

Efficacy and tolerability of a β-1 selective β blocker, bisoprolol, as a first-line antihypertensive in Indian patients diagnosed with essential hypertension (BRIGHT): an open-label, multicentric observational study

OBJECTIVES

This study was aimed to evaluate the efficacy and tolerability of bisoprolol, in Indian patients diagnosed with stage I essential hypertension as first-line drug.

DESIGN

This was an open-label, phase IV, multicentric prospective study.

SETTINGS

239 outpatient centres across India.

PARTICIPANTS

After ethical approval, patients who were willing to sign informed consent, who are newly diagnosed with JNC VII stage I essential hypertension (systolic blood pressure 140-159 mm Hg or diastolic blood pressure 90-99 mm Hg) and who are prescribed bisoprolol were enrolled in the study. Patients with significant organ disease or complications, women of childbearing age refusing reliable contraceptive method, patients with known contraindications (like symptomatic bradycardia, significant atrioventricular blockade, sick sinus syndrome) and patients with known hypersensitivity reactions to bisoprolol and unwilling patients were excluded. PRIMARY AND SECONDARY OUTCOMES MEASURES: The primary outcome measure was percentage of patients achieving blood pressure (BP) ≤140/90 mm Hg at the end of 12 weeks, while multiple secondary outcome measures were assessed.

RESULTS

Of 2418 patients screened, 2161 patients were recruited (66.64% men, mean age 51.7±9.8 years, smokers 19.19%) and 2131 (96.44%) patients achieved BP control. There was significant reduction in systolic blood pressure (-25.29; SD: 13.22 mm Hg), diastolic blood pressure (-14.14; SD: 7.67 mm Hg) and heart rate (-12/min; SD: 6.15) compared with baseline (all p values <0.05). The median dose of bisoprolol and average period required for the response were 5 mg/day and 33 days, respectively. Bisoprolol was found to be well tolerated in the patients up to 10 mg/day. A total of 1.9% patients showed adverse events, which were mild to moderate in severity without any severe adverse event. None required treatment withdrawal.

CONCLUSION

Bisoprolol is an effective and safe option to control BP. Thus, it can be used as one of the first-line antihypertensive in Indian patients.

In vivo evidence of positive inotropism of EMD 57033 through calcium sensitization

The previous separation of the racemic cardiotonic thiadiazinone derivative EMD 53998 yielded two enantiomers with different pharmacologic properties: EMD 57,033, a potent Ca2+ sensitizer with some residual phosphodiesterase III (PDE III) inhibition, and EMD 57,439, a pure PDE III inhibitor. Although numerous in vitro studies demonstrated the ability of EMD 57,033 to increase the responsiveness of cardiac contractile proteins to Ca2+, in vivo evidence for such an action is lacking. Because there is no possibility of directly proving Ca2+ sensitization in vivo, we attempted to exclude PDE III inhibition as a major contributing component of the positive inotropic action of EMD 57,033. In anesthetized rats, EMD 57,033 increased left ventricular (LV) first derivative of change in systolic pressure over time (dP/dt max) without affecting blood pressure. In contrast, the PDE III-inhibitory enantiomer EMD 57,439 decreased blood pressure. The pattern of hemodynamic effects in anesthetized dogs revealed similar differences between EMD 57,033 and PDE inhibitors. Thus the increase in LV dP/dt max in response to EMD 57,033 was not accompanied by changes of heart rate and blood pressure. As expected for PDE inhibitors, pimobendan and milrinone increased cardiac contractile force in dogs, concomitant, however, with tachycardia, hypotension, and a decrease in total peripheral resistance. When regional contractility was measured separately in two different areas of the dog myocardium, the positive inotropic action of the PDE inhibitors pimobendan and milrinone was antagonized by local coronary infusion of acetylcholine. The cardiotonic effect of the Ca2+ sensitizer EMD 57,033 was entirely resistant to inhibition by acetylcholine. In conscious dogs, beta-blockade markedly attenuated the increase in LV dP/dt max produced by two different doses of the PDE III inhibitor EMD 57,439. In contrast, a dose of EMD 57,033 equieffective in positive inotropic action with the lower dose of EMD 57,439 remained unaffected by < b tau-blockade. We concluded (a) that EMD 57,033 increases cardiac contractile force in two species in vivo, (b) that this action is independent of the cardiac cyclic adenosine monophosphate (AMP) system, (c) that EMD 57,033 does not reduce blood pressure and increase heart rate, an action indicative of PDE inhibition, and (d) that, on the basis of numerous previous in vitro findings, the mechanism of action of EMD 57,033, also in vivo, is consistent with sensitization of the cardiac myofibrils to Ca2+. Of special importance is the finding that this Ca2+ sensitizer at appropriate doses may be able to improve systolic function without adverse effects on diastolic function, as indicated by a slight decrease in left ventricular end-diastolic pressure.

Bisoprolol improves perfusion of ischaemic myocardium in anaesthetized pigs

1. The ability of the cardioselective beta-adrenoceptor antagonist bisoprolol ((+/-)-1-[4-(2-isopropoxyethoxymethyl)-phenoxy]-3-isopropyl-amino -2-propanol hemifumarate, EMD 33512) to suppress isoprenaline-induced increases in heart rate and maximal rate of rise in left ventricular pressure (LVdP/dtmax) was studied in 6 anaesthetized pigs given 4 cumulative doses (16, 64, 256 and 1024 micrograms kg-1). Bisoprolol was about 2 times more effective in suppressing isoprenaline-induced increases in LVdP/dtmax than those in heart rate. 2. In 8 animals which had a partial stenosis of the left anterior descending coronary artery (LADCA), the effects of 3 consecutive doses (50, 200 and 750 micrograms kg-1) of bisoprolol were studied on systemic haemodynamics, regional myocardial perfusion and function. The effects of the drug were compared with those obtained in a group of 9 animals with LADCA stenosis which did not receive any treatment. 3. The lowest dose of bisoprolol (50 micrograms kg-1) increased perfusion of the ischaemic myocardium (which had been reduced from 123 +/- 20 ml min-1 100 g-1 to 42 +/- 11 ml min-1 100 g-1) by 21 +/- 10 ml min-1 100 g-1 (P less than 0.05). In particular the subendocardial layers, which were most severely affected by the stenosis (a decrease from 128 +/- 19 ml min-1 100 g-1 to 20 +/- 6 ml min-1 100 g-1) benefited from the administration of the drug (an increase of 30 +/- 10 ml min-1 100 g-1). Perfusion of the subepicardium was not significantly affected. With the higher dose only a minor additional improvement in perfusion of the ischaemic myocardium was observed. 4. The negative chronotropic response is the most likely factor leading to the improvement in perfusion. 5. Myocardial wall thickening, which decreased from 41 +/- 2% to 9 +/- 4% (P less than 0.05) due to the hypoperfusion, did not improve after administration of the drug. This lack of improvement may possibly be due to the duration of ischaemia before and the magnitude of the flow deficit after bisoprolol administration. 6. Between 15 and 60 min of ischaemia, 5 of the 9 untreated animals had an episode of ventricular fibrillation compared with only 1 of the 8 animals treated with bisoprolol, in spite of an initially larger flow reduction in the treated animals. The more homogeneous flow distribution after bisoprolol might account for the lower incidence of arrhythmias in this group. 7. It was demonstrated that bisoprolol improves perfusion of ischaemic myocardium in anaesthetized pigs even at doses (50.pgkg-1) that only moderately antagonize isoprenaline-induced cardiostimulatory effects.

Cardiopulmonary effects of celiprolol and bisoprolol in serotonin-infused cats

The effects of celiprolol and bisoprolol on cardiopulmonary function in serotonin-infused cats were compared. Celiprolol reversed the bronchoconstrictive effect of serotonin at doses greater than or equal to 1.0 mg/kg. Also, decreases in mean arterial pressure and heart rate were noted after administration of 3-10 and 10 mg/kg celiprolol, respectively. In contrast, bisoprolol tended to induce bronchoconstriction. Reductions in mean arterial pressure and heart rate were observed with 1 or 3 mg/kg. Bisoprolol administration at 10 mg/kg was lethal. The unique ability of celiprolol to induce bronchodilation enhances its therapeutic potential.