Pharmacology of antihypertensive agents with multiple actions

Medication adherence in patients with apparent resistant hypertension: findings from the SYMPATHY trial

AIMS

Hypertension is only controlled in approximately 35% of the patients, which could be partially due to nonadherence. Recently, bioanalytical assessment of adherence to blood pressure (BP) lowering drugs has gaining interest. Our aim was to explore possible determinants of nonadherence in treatment resistant hypertension, assessed by objective screening for antihypertensive agents in serum. The secondary aim was to study the effect of adherence on the change in BP.

METHODS

This project was a substudy of SYMPATHY; an open-label randomized-controlled trial to assess the effect of renal denervation on BP 6 months after treatment compared to usual care in patients with resistant hypertension. Stored serum samples were screened for antihypertensive agents to assess adherence at baseline and 6 months after intervention, using liquid chromatography-tandem mass spectrometry. Office and 24-h BP were measured on the same day as blood was sampled. Patients and physicians were unaware of adherence measurements.

RESULTS

Ninety-eight baseline and 83 6-month samples were available for analysis. Sixty-eight percent [95% confidence interval (CI) 59-78%] of the patients was nonadherent (n = 67). For every onw pill more prescribed, 0.785 [95%CI 0.529-0.891] prescribed pill was less detected in blood. A decrease of one pill in adherence between baseline and 6 months was associated with a significant rise in office systolic BP of 4 (95%CI 0.230-8.932) mmHg.

CONCLUSION

Objective measurement of BP lowering drugs in serum, as a tool to assess adherence, showed that nonadherence was very common in patients with apparent resistant hypertension. Furthermore, the assessment results were related to (changes in) blood pressure. Our findings provide direct and objective methodology to help the physician to understand and to improve the condition of apparent resistant hypertension.

Electrophysiologic Effects of Beta-blocking Agent, Tilisolol, on Isolated Guinea Pig Ventricular Myocytes

BACKGROUND: Electrophysiologic effects of a beta-blocking agent, tilisolol, were studied with isolated guinea pig ventricular myocytes using the whole cell patch clamp technique. METHODS AND RESULTS: Tilisolol at 10 µM or higher concentrations prolonged action potential duration (APD) at 90% repolarization (APD(90)) and at 100 µM or higher concentrations shortened APD at 20% repolarization (APD(20)) without changes in resting membrane potential. At 10 µM concentration tilisolol prolonged APD(90) from 236.6 +/- 55.3 ms in the control to 253.4 +/- 52.4 ms (n = 16; P <.01), while APD(20) was unaffected. At 100 µM tilisolol, APD(20) was shortened from 143.6 +/- 15.7 ms in the control to 133.7 +/- 22.6 ms (n = 8; P <.05). Under voltage clamp, tilisolol decreased the delayed rectifier K(+) current (I(K1)). Applications of 10 µM and 100 µM tilisolol reduced the maximal conductance of I(K) by 35.7 +/- 3.5% and 47.4 +/- 3.5% of the control, respectively, without changes in voltage dependence (n = 10). Tilisolol at 100 µM decreased the L-type Ca(2+) current (I(Ca.L)) by 22.0 +/- 9.8% (n = 6) of the control, and the inactivation curve was shifted to a hyperpolarizing direction. CONCLUSIONS: Tilisolol has a direct membrane action to depress I(K) and I(Ca.L), in addition to its beta-receptor blocking action.

Effects of tilisolol on ischemic myocardial metabolism in dogs

The effects of tilisolol on ischemic myocardial energy and carbohydrate metabolism were examined, and compared with those of propranolol. Ischemia was induced by ligating the left anterior descending coronary artery for 3 or 30 min in anesthetized open-chest dogs, 5 min after saline, tilisolol (0.2 mg.kg-1, i.v.), or propranolol (1 mg.kg-1, i.v.) injection. During ischemia, the myocardial energy stores were depleted, and the levels of glycolytic intermediates were altered, associated with ST segment elevation and TQ segment depression of the epicardial electrocardiogram. Tilisolol prevented the myocardial energy depletion and alterations of carbohydrate metabolism caused by 3 min of ischemia, to the same extent as did propranolol. Even 30 min after ischemia, the prevention of these ischemic changes was sustained by tilisolol, but not by propranolol. Tilisolol briefly reduced the ST segment elevation and TQ segment depression induced by ischemia. These results suggest that the protective effects of tilisolol on the ischemic myocardium are more potent and long-lasting than those of propranolol.

Pathophysiologic and pharmacologic rationales for clinical management of chronic heart failure with beta-blocking agents

An understanding of the important role of neurohormonal compensatory mechanisms in heart failure has been translated into therapeutic options that can improve cardiac function, alter disease progression, and improve survival. Angiotensin-converting enzyme inhibitors are of proven benefit in this regard, and beta-adrenergic receptor antagonists are potentially another such class of agents. By inhibiting the myocardial effects of chronic adrenergic activation, beta blocking agents may improve left ventricular function or delay its deterioration in patients with heart failure. Aside from blocking beta-adrenergic receptors, other ancillary properties inherent in third-generation beta-blocking agents (such as vasodilation) may exert additional favorable effects. Clinical data generated in subjects with heart failure indicate that beta-antagonist therapy exerts its physiologic and clinical effects through neurohormonal antagonism, generally analogous to angiotensin-converting enzyme inhibitors. Virtually all controlled long-term studies show that beta-blocking agents improve cardiac function and hemodynamics in patients with chronic heart failure, but large-scale trials are needed to ascertain a favorable effect on the natural history of heart failure.

Acute hemodynamic effects of carvedilol in comparison with propranolol in patients with coronary heart disease

In a randomized, double-blind study oral doses of 50 mg carvedilol (Dilatrend) were compared with 40 mg propranolol in 16 male patients with coronary heart disease, CHD [12 without significant stenoses following percutaneous transluminal coronary angioplasty (PTCA), 4 with multivessel disease]. Bicycle ergometry in the supine position was performed before and 80 min after drug application; measurements were done at rest, during and after exercise. Clinically, the total exercise time and the onset of angina and exhaustion were noted, while the investigated hemodynamic parameters were heart rate, systemic and pulmonary pressures and resistances, cardiac index, and lower limb blood flow. Clinically, carvedilol improved the exercise tolerance more than propranolol as regards angina and exhaustion. Hemodynamically, carvedilol did not lead, as the classic betablocker propranolol does, to an increase in systemic or pulmonary resistance, to a decrease in cardiac output, or to an increase of the pulmonary capillary wedge pressure during exercise, but instead caused opposite changes. In contrast to propranolol, the post exercise lower limb blood flow had increased significantly. The differences in action between the two betablockers can be explained by the vasodilating properties of carvedilol. Due to these acute effects, carvedilol may be preferred to propranolol in the treatment of CHD patients with hypertension, peripheral occlusive artery disease, and/or coronary vasospasm.