An evaluation of the efficacy and safety of doxazosin in hypertension associated with renal dysfunction. The Japanese Doxazosin Study Group

Usefulness of the .ALPHA.1-Blocker Doxazosin as a Third-Line Antihypertensive Drug

It has been reported that a substantial majority of hypertensives receive insufficient blood pressure (BP) control. As combination therapy for the treatment of hypertension, Ca channel blockers (CCBs), angiotensin II (AII) receptor blockers (ARBs), and/or AII-converting enzyme (ACE) inhibitors are mainly prescribed, while the efficacy of alpha(1)-blockers in such combination therapy remains unknown. The aim of this study was to investigate the efficacy of a low dose of an alpha(1)-blocker added to combination therapy with CCBs and either ARBs or ACE inhibitors for the treatment of hypertension. Subjects were 41 hypertensive patients (23 women and 18 men, mean age 66+/-12 years) who had been followed at the National Kyushu Medical Center. All patients showed poor BP control despite haven taken a combination of CCBs and ARBs or ACE inhibitors for more than 3 months. Doxazosin at a dose of 1 to 2 mg was added to each treatment regimen. The changes in various clinical parameters, including BP and blood chemistry, following the addition of doxazosin were then evaluated. The mean follow-up period was 170 days. BP decreased from 152+/-14/81+/-12 mmHg to 135+/-14/70+/-11 mmHg after the addition of doxazosin at a mean dose of 1.5 mg/day (p<0.001). When good systolic blood pressure (SBP) control was defined as <140 mmHg, the prevalence of patients with good SBP control increased from 24% to 61% (p<0.01). Similarly, the prevalence of patients with good diastolic blood pressure (DBP) control (<90 mmHg) increased from 78% to 98% (p<0.01). Patients whose SBP decreased more than 10 mmHg (n=25) showed significantly higher baseline SBP, serum total cholesterol and low-density lipoprotein (LDL) cholesterol levels compared to those who showed less SBP reduction (<10 mmHg) (n=16, p<0.01). Comparable BP reductions were obtained between obese (body mass index [BMI] > or =25, DeltaBP at 3 months: -15+/-15/-12+/-9 mmHg, n=18) and non-obese (BMI<25, DeltaBP: -14+/-19/-7+/-8 mmHg, n=23) patients. The results suggest that addition of a low dose of the alpha(1)-blocker doxazosin effectively reduces BP in patients taking CCBs and ARBs or ACE inhibitors. Thus, doxazosin seems to be useful as a third-line antihypertensive drug.

Efficacy and safety of doxazosin GITS in hypertensive renal transplant patients: comparison of 8 and 4 mg

BACKGROUND

Hypertension (HT), a prevalent complication in renal transplant patient (RT), must be accurately treated because cardiovascular disease is the leading cause of death and of chronic graft dysfunction. Sympathetic activity may contribute to HT in RT, yielding the rationale to suspect that doxazosin, an alpha1-adrenergic receptor inhibitor, may lower blood pressure (BP). The aim of this study was to evaluate the efficacy and safety of doxazosin GITS (4 and 8 mg) in RT.

METHODS

Twenty-three hypertensive RT received doxazosin 4 mg once daily for 4 weeks (W4) followed by a 4-week washout (W0) and 17/23 treated with doxazosin 8 mg for 4 more weeks (W8) due to persistent HT. All patients underwent 24-hour ambulatory blood pressure monitoring (ABPM) after W0, W4, and W8. Laboratory tests were performed, adverse events recorded, and prostatic symptomatology examined. Statistical analysis included Saphiro-Wilks, Student t, ANOVA, Wilcoxon, or Friedman tests.

RESULTS

The systolic, diastolic, and mean BP were significantly lowered at W4 in awake (P<.001) and 24 hour period (P<.005) but not sleep recordings. Doxazosin 8 mg had no significant additional effect to lower BP at any period. Normotension was reached in 13% and 21.7% of patients at W4 and W8, respectively. Palpitations were the only reported adverse event after treatment (incidence similar to placebo). There was no significant change in the laboratory values.

CONCLUSIONS

Doxazosin (-4 mg) effectively decreased BP in awake and 24-hour periods without a significant improvement during sleep. A double dose of the drug added little benefit. Optimal BP was reached by an insufficient number of patients. Doxazosin proved to have a good tolerance and safe profile. This results suggest that doxazosin should be considered a good add-on treatment to other antihypertensive drugs in RT.

Calcium channel blockers blunt postural cutaneous vasoconstriction in hypertensive patients

The aim of this work was to test whether calcium channel blockers interfere with skin vasoconstrictor reflexes that minimize postural increases in capillary pressure and avoid fluid extravasation and eventually subcutaneous edema. Studies were conducted in 23 untreated mild to moderate essential hypertensives; drugs, either calcium channel blockers or not, were given for 2 weeks according to a crossover, sequence-randomized design. Skin blood flow was measured by laser Doppler flowmetry in two skin areas: (1) the dorsum of the foot, where arteriovenous anastomoses are poorly represented, and (2) the plantar surface of the great toe, where those anastomoses are predominant. Determinations were obtained both with the foot at heart level and with it placed passively 50 cm below the heart level; percent flow changes from the horizontal to the dependent position were the measure of postural vasoconstriction. Two dihydropyridine derivatives, amlodipine (10 mg UID) and nifedipine (60 mg UID), and verapamil (240 mg BID), a chemically unrelated compound, diminished to similar extents the postural fall in skin blood flow at the dorsum of the foot. Blockade of alpha1-adrenergic and AT-1 subtype angiotensin II receptors by doxazosin (4 mg UID) and losartan (50 mg UID), respectively, exerted no effect. Postural skin blood flow responses at the plantar surface of the great toe were unmodified during the pharmacological trials. Thus, calcium channel blockers of different chemical origins antagonized postural skin vasoconstriction at the dorsum of the foot. The data indicate altered postural capillary blood flow regulation, since arteriovenous anastomoses are anatomically absent at this site; the effect was independent of either alpha1-adrenoceptor or angiotensin II receptor antagonism. Interference with skin postural vasoconstrictor mechanisms may result in net filtration of fluid to the extravascular compartment. This mechanism might explain the as yet unknown pathogenesis of ankle edema during treatment with calcium antagonists.

Doxazosin. An update of its clinical pharmacology and therapeutic applications in hypertension and benign prostatic hyperplasia

Doxazosin is a long-acting alpha 1-adrenoceptor antagonist structurally related to prazosin and terazosin. Its antihypertensive effect is produced by a reduction in the smooth muscle tone of peripheral vascular beds resulting in a decrease in total peripheral resistance without significant effect on cardiac output or heart rate. In benign prostatic hyperplasia, doxazosin's effect of relieving bladder outflow obstruction is produced through a reduction in prostatic tone mediated via alpha 1-adrenoceptor blockade. In most comparative trials doxazosin has proven to be equally effective as the comparator drug in the treatment of mild to moderate hypertension. It has been used in a variety of patient populations including the elderly, Blacks, smokers, and patients with concomitant disease states such as renal dysfunction, hypercholesterolaemia, non-insulin dependent diabetes mellitus (NIDDM) and respiratory disease. Doxazosin has also been used successfully in combination with beta-adrenoceptor antagonists, diuretics, calcium channel antagonists, and angiotensin-converting enzyme inhibitors in patients with hypertension that is uncontrolled with monotherapy. Doxazosin has a beneficial effect on some of the risk factors associated with coronary heart disease including elevated serum lipid levels, impaired glucose metabolism, insulin resistance and left ventricular hypertrophy. Modest decreases in total cholesterol, low density lipoprotein cholesterol and triglycerides are seen with doxazosin therapy while small increases in high density lipoprotein cholesterol and the high density lipoprotein cholesterol/total cholesterol ratio are consistently reported. Some studies have reported an improvement in glucose tolerance although this effect has been more consistently seen in nondiabetic patients than in patients with NIDDM. Additionally, doxazosin produces a similar reduction in left ventricular hypertrophy to other antihypertensive agents. Modelling-based calculations suggest that doxazosin significantly reduces the risk of developing coronary heart disease in patients with mild to moderate hypertension, although this remains to be confirmed in long term prospective studies. Doxazosin appears to be a promising agent in the treatment of urinary symptoms associated with benign prostatic hyperplasia. Similar to other alpha 1-adrenoceptor antagonists, doxazosin treatment produces increases in peak and mean urinary flow rates and improves other objective and symptomatic measures.(ABSTRACT TRUNCATED AT 400 WORDS)