Effect of administration and withdrawal of doxazosin on ambulatory blood pressure in patients with essential hypertension

Add-on therapy with a nighttime dose of doxazosin in patients with uncontrolled hypertension: effects on autonomic modulation of the cardiovascular system

This study was designed to determine whether or not the addition of a single nighttime dose of doxazosin in extended-release form (GITS; gastrointestinal therapeutic system) would affect the autonomic modulation of the cardiovascular system in patients with uncontrolled hypertension treated with a multi-drug regimen. Resting 5-min noninvasive finger blood pressure and ECG signals, as well as 24-h Holter ECGs, were recorded in 30 patients with uncontrolled hypertension on multi-drug treatment before and after 16-week add-on therapy with doxazosin GITS. Cardiovascular autonomic modulation was evaluated by spectral analysis of heart rate variability (HRV) and a cross-correlation method for spontaneous baroreflex sensitivity (BRS) in 5-min resting recordings, and by the analysis of Poincaré plots and phase-rectified signal averaging of the duration of cardiac cycles in 24-h ECG recordings. This combined therapy significantly reduced systolic pressure (19.4+/-3.5 mmHg; p<0.0001), diastolic blood pressure (9.4+/-2.0 mmHg; p=0.0003), and pulse pressure (10.0+/-2.8 mmHg; p=0.0021). Concomitantly, there was a significant increase in resting spontaneous BRS (p=0.0191) and increases in 24-h short-term (p=0.0129) and total (p=0.0153) HRV, but with no significant change in heart rate or other measures of HRV. The improvements in HRV and BRS were observed mainly in patients already treated with thiazide diuretics. There was a significant association (r=0.49; p=0.0065) between the degree of change in diastolic blood pressure and short-term HRV caused by the combined treatment. The addition of 4 mg doxazosin GITS to multi-drug antihypertensive therapy is associated with an improvement in cardiovascular autonomic control.

Add-on therapy with doxazosin in patients with hypertension influences arterial stiffness and albuterol-mediated arterial vasodilation

AIMS

Doxazosin is an antihypertensive agent with largely unknown effects on arterial stiffness and vasodilation. The aim of this study was to determine the effect of the addition of doxazosin extended-release (ER) to the standard management of hypertension in patients with inadequately controlled blood pressure (BP) on arterial stiffness and arterial vasodilation.

METHODS

Twenty patients with inadequately controlled hypertension were treated with 4 mg doxazosin ER daily for 16 weeks as an adjunct to their existing antihypertensive regimen.

RESULTS

Doxazosin ER add-on therapy was associated with significantly reduced systolic (P < 0.0001) and diastolic (P = 0.0003) BP, improved arterial stiffness (determined by digital volume pulse analysis (P = 0.048) and albuterol-mediated arterial vasodilation (P = 0.030).

CONCLUSIONS

Add-on therapy with 4 mg of doxazosin ER daily reduces BP and arterial stiffness and improves arterial vasodilation in response to adrenergic stimulation.

Effects of doxazosin on ambulatory blood pressure and sympathetic nervous activity in hypertensive Type 2 diabetic patients with overt nephropathy

AIMS

Few studies have reported the effect of alpha(1)-adrenergic antagonists on 24-h blood pressure (BP) and sympathetic nervous activity in hypertensive patients with diabetic nephropathy. We assessed the effects of doxazosin on 24-h BP and spectral analysis of heart rate variability in hypertensive Type 2 diabetic patients with macroalbuminuria and compared the results with those in hypertensive Type 2 diabetic patients with normoalbuminuria and non-diabetic patients with essential hypertension.

METHODS

Thirty-three patients in the macroalbuminuric group, 24 patients in the normoalbuminuric group, and 34 patients with essential hypertension underwent ambulatory BP monitoring before and after doxazosin treatment. Spectral analysis was performed to calculate the high-frequency (HF) components, a marker of parasympathetic nervous activity, and the low-frequency (LF) components, a marker of sympathetic nervous activity.

RESULTS

Doxazosin decreased waking (from 158 +/- 17/88 +/- 10 to 148 +/- 15/80 +/- 7 mmHg, P = 0.001 for systolic and P < 0.001 for diastolic BP) and sleeping BP (146 +/- 20/79 +/- 10 to 137 +/- 17/72 +/- 9 mmHg, P < 0.001 and P < 0.001) in the macroalbuminuric group, but only decreased waking BP in the essential hypertension group (157 +/- 16/91 +/- 9 to 145 +/- 15/84 +/- 11 mmHg, P < 0.001 and P < 0.001) and normoalbuminuric group (159 +/- 15/89 +/- 9 to 150 +/- 16/82 +/- 10 mmHg, P = 0.014 and P < 0.001). Doxazosin decreased waking (from 1.48 +/- 0.11 to 1.42 +/- 0.12, P = 0.001) and sleeping (1.46 +/- 0.11 to 1.40 +/- 0.13, P = 0.001) LF components [unit: log(ms(2)/Hz)] only in the macroalbuminuric group without changing HF components. The normoalbuminuric and essential hypertension groups showed no differences (P = 0.637 and 0.492) in LF components during sleep.

CONCLUSIONS

Doxazosin may be an antihypertensive agent that decreases both waking and sleeping BP through inhibiting sympathetic nervous activity in macroalbuminuric diabetes patients.

The implications of noncompliance with antihypertensive medication

Given the clear evidence that reducing blood pressure decreases the vascular complications of hypertension, loss of efficacy represents the principal complication of noncompliance with antihypertensive therapy. Withdrawal symptoms are also important and occur after abruptly stopping beta-blockers and centrally-acting antihypertensive drugs. Very few studies have been conducted to assess the impact of missing 1 or 2 doses of an antihypertensive agent on short term control of blood pressure. A high trough to peak ratio (> 50%) for a once-daily medication suggests a long duration of action. However, methodological problems in the design of the studies to determine trough to peak ratios make comparisons between various medications very difficult. In general, however, stopping a drug with a low through to peak ratio is more likely to result in loss of antihypertensive effect than a drug with a high ratio. Poor compliance in dose-escalating studies with antihypertensive agents may have resulted in excessively high dose recommendations in clinical trials.