Doxazosin and congestive heart failure

Adverse drug reactions in patients with cardiovascular disease

Adverse drug reactions (ADRs) occur frequently in modern medical practice, increasing morbidity and mortality and inflating the cost of care. Patients with cardiovascular disease are particularly vulnerable to ADRs due to their advanced age, polypharmacy, and the influence of heart disease on drug metabolism. The ADR potential for a particular cardiovascular drug varies with the individual, the disease being treated, and the extent of exposure to other drugs. Knowledge of this complex interplay between patient, drug, and disease is a critical component of safe and effective cardiovascular disease management. The majority of significant ADRs involving cardiovascular drugs are predictable and therefore preventable. Better patient education, avoidance of polypharmacy, and clear communication between physicians, pharmacists, and patients, particularly during the transition between the inpatient to outpatient settings, can substantially reduce ADR risk.

Alpha1-adrenergic blockers: current usage considerations

Alpha1-adrenergic-blocking drugs are effective in reducing blood pressure and do so in a fashion comparable to most other antihypertensive drug classes. These compounds are most effective in patients in the upright position, reducing systolic and diastolic pressures by 8%-10%. Alpha1-adrenergic-blocking drugs incrementally reduce blood pressure when combined with most drug classes and are the only antihypertensive drug class to improve plasma lipid profiles. Alpha1-adrenergic-blocking drugs are also accepted as important elements of the treatment plan for symptomatic benign prostatic hypertrophy. Dose escalation of an alpha1-adrenergic-blocking drug can trigger renal Na+ retention, and the ensuing volume expansion can attenuate its blood pressure-lowering effect. Orthostatic hypotension can occur with these compounds, particularly when a patient is volume-contracted. Dizziness, headache, and drowsiness are common side effects with alpha1-adrenergic blockers. A modest decline in the use of doxazosin and other alpha1-adrenergic-blocking drugs has occurred coincident to the early termination of the doxazosin treatment arm in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial.

Effects of Doxazosin and Irbesartan on Blood Pressure and Metabolic Control in Patients with Type 2 Diabetes and Hypertension

The objective of this trial was to compare the metabolic effects of long-term treatment with doxazosin to those of irbesartan in patients with type 2 diabetes and hypertension. We evaluated 96 hypertensive diabetic patients who were randomized to 12 months of double-blind treatment with doxazosin 4 mg/d or irbesartan 300 mg/d. At the end of the study, systolic and diastolic blood pressure (SBP and DBP) were significantly reduced from 152 to 140 mm Hg and from 97 to 87 mm Hg, respectively, with doxazosin (P < 0.01). SBP and DBP were reduced from 150 to 134 mm Hg and from 94 to 83 mm Hg, respectively, with irbesartan (P < 0.01). Irbesartan had significantly better antihypertensive efficacy than doxazosin (P < 0.05). Doxazosin had the greatest effect on glucose metabolism and lipid parameters, with significant (P </= 0.05) reductions observed at study end compared with baseline in glycosylated hemoglobin, fasting plasma glucose, fasting plasma insulin, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and Homeostasis Model Assessment Index. In conclusion, both doxazosin and irbesartan reduced BP during long-term treatment, but not to recommended levels, and doxazosin had the more beneficial effect on glucose metabolism and lipid profile.

Critical role for the alpha-1B adrenergic receptor at the sympathetic neuroeffector junction

The alpha-1 adrenergic receptors (alpha(1)ARs) are critical in sympathetically mediated vasoconstriction. The specific role of each alpha(1)AR subtype in regulating vasoconstriction remains highly controversial. Limited pharmacological studies suggest that differential alpha(1)AR responses may be the result of differential activation of junctional versus extrajunctional receptors. We tested the hypothesis that the alpha(1B)AR subtype is critical in mediating sympathetic junctional neurotransmission. We measured in vivo integrated cardiovascular responses to a hypotensive stimulus (induced via transient bilateral carotid occlusion [TBCO]) in alpha(1B)AR knockout (KO) mice and their wild-type (WT) littermates. In WT mice, after dissection of the carotid arteries and denervation of aortic baroreceptor buffering nerves, TBCO produced significant pressor and positive inotropic effects. Both responses were markedly attenuated in alpha(1B)AR KO mice (change systolic blood pressure 46+/-8 versus 11+/-2 mm Hg; percentage change in the end-systolic pressure-volume relationship [ESPVR] 36+/-7% versus 12+/-2%; WT versus KO; P<0.003). In vitro alpha(1)AR mesenteric microvascular contractile responses to endogenous norepinephrine (NE; elicited by electrical field stimulation 10 Hz) was markedly depressed in alpha(1B)AR KO mice compared with WT (12.4+/-1.7% versus 21.5+/-1.2%; P<0.001). In contrast, responses to exogenous NE were similar in alpha(1B)AR KO and WT mice (22.4+/-7.3% versus 33.4+/-4.3%; NS). Collectively, these results demonstrate a critical role for the alpha(1B)AR in baroreceptor-mediated adrenergic signaling at the vascular neuroeffector junction. Moreover, alpha(1B)ARs modulate inotropic responses to baroreceptor activation. The critical role for alpha(1B)AR in neuroeffector regulation of vascular tone and myocardial contractility has profound clinical implications for designing therapies for orthostatic intolerance.

Antihypertensive therapy: special focus on drug interactions

Today, the lifetime risk of patients aged 55-65 years to receive antihypertensive drugs approaches 60%. Yet, recent trials suggest that hypertension is not adequately controlled in the majority of patients. The prevalence of hypertension increases with advancing age, as does the prevalence of comorbid conditions and the total number of medications taken. Multi-drug therapy, advancing age and comorbid conditions are also key risk factors for adverse drug reactions and drug interactions. In this review, the authors evaluate the most frequently used antihypertensive drugs (diuretics, beta-adrenergic blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, angiotensin II receptor Type 1 blockers and alpha-adrenergic blockers) with special reference to pharmacodynamic and pharmacokinetic drug interactions. As the spectrum of drugs prescribed is constantly changing, safety yesterday does not imply safety today and safety today does not imply safety tomorrow. Furthermore, therapeutic efficacy should not be neglected over concerns regarding drug interactions. Many patients are at risk of clinically relevant drug interactions involving antihypertensive drugs but, presently, even more patients may be at risk of suffering from the consequences of their inadequately treated hypertension. In this respect, the authors discuss controversial viewpoints on the overall clinical relevance of drug interactions occurring at the level of cytochrome P450 metabolism.

The importance of blood pressure control in the patient with diabetes

In individuals with diabetes mellitus, higher risk for renal and cardiovascular disease is seen with blood pressure levels >130/80 mm Hg. Findings of several studies, as well as new guidelines, indicate that individuals with diabetes will benefit from more aggressive treatment of hypertension. Angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, diuretics, beta-adrenoceptor blockers, and calcium-channel blockers are effective antihypertensive agents in type 2 diabetes. Moreover, combinations of these agents are frequently required to reach the target blood pressure of <130/80 mm Hg and reduce risk for renal and cardiovascular events. All of these agents have demonstrated benefits in treating patients. Clinical evidence also indicates that the new vasodilating beta-blockers offer advantages beyond blood pressure control, including cardiovascular risk reduction without exacerbating metabolic parameters. With increased awareness of the need for aggressive treatment of hypertension, clinicians can provide significant benefit to their patients with diabetes. The new beta-blockers may play an important role in achieving blood pressure goals.

α1-Adrenergic Receptors and Their Inhibitors in Lower Urinary Tract Symptoms and Benign Prostatic Hyperplasia

PURPOSE

We provide a comprehensive overview of the role of alpha1-adrenergic receptors (alpha1ARs) as critical mediators of lower urinary tract symptoms (LUTS) and pathophysiology in benign prostatic hyperplasia (BPH), and we review the pharmacological antagonists of alpha1ARs.

MATERIALS AND METHODS

A review was performed of pertinent studies in the literature relating to the pathophysiology of LUTS and BPH, focusing on the role of alpha1ARs, and of clinical trial and practice data evaluating the different agents that inhibit these receptors.

RESULTS

Further characterization of the alpha1AR gene family indicates that 3 receptor subtypes exist in humans. Their different distribution between urinary tract and cardiovascular tissues has provided a strategy for the development of improved therapeutic agents. Since excessive activity of the alpha1aAR and alpha1dAR subtypes appears to be a common feature in symptomatic BPH and alpha1aARs are enriched in prostatic tissue, drugs that demonstrate high alpha1aAR selectivity have attracted attention. Tamsulosin, which has high affinity for alpha1aAR and alpha1dAR subtypes but not for alpha1bAR, shows efficacy similar to the nonsubtype selective agents terazosin and doxazosin. It is associated with fewer cardiovascular side effects, although it has some ejaculatory side effects. The nonsubtype selective agent alfuzosin also demonstrates efficacy and offers an enhanced side effect profile, particularly minimizing hypotension. Other agents with super selective specificity for the alpha1aAR subtype are under investigation.

CONCLUSIONS

Further advances in the treatment of LUTS associated with BPH may depend not only on receptor subtype selectivity, but also on other pharmacokinetic and pharmacodynamic factors.

Premature termination of clinical trials--lessons learned

Controlled clinical trials in cardiovascular disease are the cornerstone for therapeutic advances in this field of medicine. Since the introduction of the concept of controlled clinical trials there has been substantial progress in the design, conduct, and analysis of such studies. A growing awareness of ethical issues emerging from such trials has heightened public awareness, increased investigator scrutiny, and reinforced the need for interim data analysis. A benefit of such interim analyses is that either an entire clinical trial or a specific treatment limb can be stopped if the observed findings argue for premature termination. For example, highly positive findings, as were noted in the HOPE Study (Heart Outcomes Prevention Evaluation), led to its being stopped after 4.5 years of treatment, which was 1 year early. Alternatively, the doxazosin treatment limb of the ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) and the amlodipine treatment limb of AASK (African American Study of Kidney Disease and Hypertension) were stopped early because of negative findings with each respectively. Finally, economic considerations can enter into the decision to close a study early as was the case in the CONVINCE (Controlled Onset Verapamil Investigation of Cardiovascular End Points) trial. Most such decisions rely heavily on information obtained from independent data and safety monitoring boards. Such boards ensure patient safety by providing an unbiased ongoing review of data, which would otherwise be unavailable until a study's completion. Early termination of a clinical trial can have important clinical implications and, in particular, can redirect patterns of clinical practice.