Comparative and combined efficacy of doxazosin and enalapril in hypertensive patients

The Effects of Verapamil, Hydralazine, and Doxazosin on Renin, Aldosterone, and the Ratio Thereof

PURPOSE

Hydralazine, doxazosin, and verapamil are currently recommended by the Endocrine Society as acceptable bridging treatment in those in whom full cessation of antihypertensive medication is infeasible during screening for primary aldosteronism (PA). This is under the assumption that they cause minimal to no effect on the aldosterone-to-renin ratio, the most widely used screening test for PA. However, limited evidence is available regarding the effects of these particular drugs on said ratio.

METHODS

In the present study, we retrospectively assessed the changes in aldosterone, renin, and aldosterone-to-renin values in essential hypertensive participants before and after treatment with either hydralazine (n = 26) or doxazosin (n = 20) or verapamil (n = 15). All samples were taken under highly standardized conditions.

RESULTS

Hydralazine resulted in a borderline significant rise in active plasma renin concentration (19 vs 25 mIU/L, p = 0.067) and a significant fall in the aldosterone-to-renin ratio (38 vs 24, p = 0.017). Doxazosin caused declines in both plasma aldosterone concentration (470 vs 330 pmol/L, p = 0.028) and the aldosterone-to-renin ratio (30 vs 20, p = 0.020). With respect to verapamil, we found no statistically significant effect on any of these outcome variables.

CONCLUSION

We conclude that the assumption that these drugs can be used with little consequence to the aldosterone-to-renin cannot be substantiated. While it is possible that they are indeed the best option when full antihypertensive drug cessation is infeasible, the potential effects of these drugs must still be taken into account when interpreting the aldosterone-to-renin ratio.

Patients with uncontrolled hypertension or concomitant hypertension and benign prostatic hyperplasia

At optimal doses, individual antihypertensive agents lower blood pressure (BP) by an average of 10 mmHg. Many patients with hypertension, including those with stage 3 hypertension, target organ damage, or those at high risk for cardiovascular events and/or adverse effects of high-dose monotherapy, are likely to require combination antihypertensive drug treatment to achieve the recommended systolic/diastolic BP (< 140/90 mmHg). Two studies, a placebo-controlled, double-blind trial (n = 70) and a community-based, open-label trial (n = 491) investigated the antihypertensive efficacy of doxazosin, a long-acting selective alpha1-adrenoceptor blocker, as add-on therapy for uncontrolled hypertension with other antihypertensive medications and in patients with concomitant benign prostatic hyperplasia (BPH) and treated but inadequately controlled hypertension, respectively. The addition of doxazosin to baseline antihypertensive medication(s) significantly lowered BP and had a significantly positive effect on the serum lipid profile. In patients with concomitant BPH, doxazosin significantly improved all BPH symptom scores, regardless of initial symptom severity. Add-on doxazosin sufficiently reduced systolic/diastolic BP such that many patients whose hypertension was previously uncontrolled by other antihypertensive medications were able to reach goal BP (< 140/90 mmHg). Doxazosin as add-on therapy was well tolerated. In conclusion, doxazosin as add-on therapy improves BP control in hypertensive patients not at goal BP and improves lower urinary tract symptoms in patients with concomitant BPH.

Doxazosin as combination therapy for patients with stage 1 and stage 2 hypertension

The purpose of this paper is to review the role of doxazosin, a long-acting alpha(1)-blocker, as a component of combination therapy for patients with stage 1 and stage 2 hypertension and for patients with concomitant hypertension and hyperlipidemia or glucose intolerance. Recent studies that evaluated doxazosin as combination therapy in the treatment of patients with inadequately controlled hypertension and patients with concomitant hypertension and other disorders were reviewed. Data extraction was based on the tolerability and efficacy data of doxazosin in patients with hypertension. Compared with placebo, doxazosin combination therapy leads to significant improvements in sitting and standing blood pressure. Doxazosin is well tolerated, with only minor adverse effects (e.g., headache, dizziness) as the most commonly reported treatment-related complications. The studies described demonstrate that doxazosin is effective as combination therapy for patients with stage 1 and stage 2 hypertension. The positive effects of doxazosin on serum lipids make combination therapy with doxazosin an attractive treatment option for patients who have concomitant hyperlipidemia or glucose intolerance.

Videoimaging of prostatic stromal-cell contraction: an in vitro model for studying drug effects

BACKGROUND

Stromal-cell contractility is known to play an important role in the development of bladder outlet obstruction secondary to benign prostatic hyperplasia (BPH). An in vitro model of single-cell contraction was developed to investigate the effect of alpha1-adrenoceptor agonists and antagonists.

METHODS

Human prostatic stromal cells were isolated from prostatectomy and cystoprostatectomy specimens. The cells were cultured in a selective medium supplemented with growth factors and steroid hormones. The culture flasks were coated with a viscous agent to allow cell contraction. Contractions were visualized by means of a cell-culture microscope fitted with a time-lapse video system. For quantitative analysis, the percentage of contracting cells was evaluated.

RESULTS

Nineteen percent of the cells were found to contract without stimulation. Following incubation with doxazosin (10 nM, 100 nM, and 1 mM), there was a slight dose-dependent decrease in the number of spontaneously contracting cells, whereas adrenergic stimulation using 10 microM of phenylephrine led to a significant increase in the percentage of contracting cells (55%). Following incubation with 100 nM of doxazosin, the phenylephrine-induced effect was significantly reduced.

CONCLUSIONS

This simple in vitro model of cell contraction in the prostate provides a useful means of investigating drug effects on prostatic stromal cells.

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)