Alpha-adrenergic blocking drugs in clinical medicine

Structure-Based Drug Design of ADRA2A Antagonists Derived from Yohimbine

Yohimbine, a natural indole alkaloid and a nonselective adrenoceptor antagonist, possesses potential benefits in treating inflammatory disorders and sepsis. Nevertheless, its broader clinical use faces challenges due to its low receptor selectivity. A structure-activity relationship study of novel yohimbine analogues identified amino esters of yohimbic acid as potent and selective ADRA2A antagonists. Specifically, amino ester 4n, in comparison to yohimbine, showed a 6-fold higher ADRA1A/ADRA2A selectivity index (SI > 556 for 4n) and a 25-fold higher ADRA2B/ADRA2A selectivity index. Compound 4n also demonstrated high plasma and microsomal stability, moderate-to-low membrane permeability determining its limited ability to cross the blood-brain barrier, and negligible toxicity on nontumor normal human dermal fibroblasts. Compound 4n represents an important complementary pharmacological tool to study the involvement of adrenoceptor subtypes in pathophysiologic conditions such as inflammation and sepsis and a novel candidate for further preclinical development to treat ADRA2A-mediated pathologies.

Recommendations of apex health bodies remain localized: not in conformity with international implementation policy for urological disorders

In developing/underdeveloped countries there is still a great burden of adverse drug reaction (ADR), morbidity and mortality because of poor regulations and implementation of preventive measures. These countries try to copy/follow guidelines from international bodies like American Urology Association (AUA), European Association of Urology (EAU), AGS, UMC and WHO irrespective of their country of origin and success in implementation. Although recommendations of these organizations are obligatory, yet these are taken as the gold standard for good clinical practices. This manuscript highlights difference in view point of various apex health organizations in formulating health policies for prevention, diagnosis, treatment and ADR monitoring for urological disorders. Lacking role of regulatory bodies in implementation of existing policies may lead to potentially inappropriate medication and produce a great economic burden. This analysis has prompted us to recommend that these apex bodies should have better coordination in producing a single value document, make it mandatory part of curricula in medical schools for better awareness, awareness campaigns and separate reporting column in ADR form.

Effect of alpha-adrenoceptor antagonists on sexual function. A systematic review and meta-analysis

BACKGROUND

Alpha-adrenoreceptor antagonists or alpha-blockers are used in the treatment of hypertension, in the therapy of benign prostatic hyperplasia and in medical expulsive treatment of ureteral stones. These agents may affect the sexual function, with differences between drugs within the same class, depending on their selectivity for receptor subtypes. The aim of this review was to analyze the effects of alpha-blockers on sexual function.

MATERIALS AND METHODS

We conducted a systematic review and meta-analysis by searching PubMed, EMBASE and other databases for randomized controlled trials (RCTs) reporting sexual adverse effects in patients treated with alpha-blockers. Odds ratios for sexual dysfunction were calculated using random effects Mantel-Haenszel statistics.

RESULTS

Out of 608 records retrieved, 75 eligible RCTs were included in the meta-analysis. Compared with placebo, alphablockers were associated with increased odds of ejaculatory disorders both in patients with lower urinary tract symptoms (LUTS) associated to benign prostatic hyperplasia (BPH) (OR: 7.53, 95% CI: 3.77-15.02, Z = 5.73, p < 0.00001, I2 = 55%) and in patients with ureteral stones (OR: 2.88, 95% CI: 1.50-5.44, Z = 3.19, p < 0.001, I2 = 31%). Uroselective alpha-blockers showed higher odds of ejaculatory disorders. Conversely, nonselective alpha-blockers were not associated with higher odds of ejaculatory dysfunction. Silodosin was associated with increased odds of ejaculatory dysfunction compared with tamsulosin (OR: 3.52, 95% CI: 2.18-5.68, 15 series, 1512 participants, Z = 5.15, p < 0.00001, I2 = 0%). Naftopidil and alfuzosin showed lower odds of ejaculatory dysfunction compared to uroselective alpha-blockers.No statistically significant differences in the odds of erectile dysfunction were observed when alpha-blockers were compared to placebo.

Antioxidant, Cytotoxic, Genotoxic, and DNA-Protective Potential of 2,3-Substituted Quinazolinones: Structure-Activity Relationship Study

The evaluation of antioxidant compounds that counteract the mutagenic effects caused by the direct action of reactive oxygen species on DNA molecule is of considerable interest. Therefore, a series of 2,3-substituted quinazolinone derivatives (Q1-Q8) were investigated by different assays, and the relationship between their biological properties and chemical structure was examined. Genotoxicity and the potential DNA-protective effects of Q1-Q8 were evaluated by comet assay and DNA topology assay. Antioxidant activity was examined by DPPH-radical-scavenging, reducing-power, and total antioxidant status (TAS) assays. The cytotoxic effect of compounds was assessed in human renal epithelial cells (TH-1) and renal carcinoma cells (Caki-1) by MTT assay. Analysis of the structure-activity relationship disclosed significant differences in the activity depending on the substitution pattern. Derivatives Q5-Q8, bearing electron-donating moieties, were the most potent members of this series. Compounds were not genotoxic and considerably decreased the levels of DNA lesions induced by oxidants (H2O2, Fe2+ ions). Furthermore, compounds exhibited higher cytotoxicity in Caki-1 compared to that in TH-1 cells. Substantial antioxidant effect and DNA-protectivity along with the absence of genotoxicity suggested that the studied quinazolinones might represent potential model structures for the development of pharmacologically active agents.

Cardiac alpha1-adrenergic receptors: novel aspects of expression, signaling mechanisms, physiologic function, and clinical importance

Adrenergic receptors (AR) are G-protein-coupled receptors (GPCRs) that have a crucial role in cardiac physiology in health and disease. Alpha1-ARs signal through Gαq, and signaling through Gq, for example, by endothelin and angiotensin receptors, is thought to be detrimental to the heart. In contrast, cardiac alpha1-ARs mediate important protective and adaptive functions in the heart, although alpha1-ARs are only a minor fraction of total cardiac ARs. Cardiac alpha1-ARs activate pleiotropic downstream signaling to prevent pathologic remodeling in heart failure. Mechanisms defined in animal and cell models include activation of adaptive hypertrophy, prevention of cardiac myocyte death, augmentation of contractility, and induction of ischemic preconditioning. Surprisingly, at the molecular level, alpha1-ARs localize to and signal at the nucleus in cardiac myocytes, and, unlike most GPCRs, activate "inside-out" signaling to cause cardioprotection. Contrary to past opinion, human cardiac alpha1-AR expression is similar to that in the mouse, where alpha1-AR effects are seen most convincingly in knockout models. Human clinical studies show that alpha1-blockade worsens heart failure in hypertension and does not improve outcomes in heart failure, implying a cardioprotective role for human alpha1-ARs. In summary, these findings identify novel functional and mechanistic aspects of cardiac alpha1-AR function and suggest that activation of cardiac alpha1-AR might be a viable therapeutic strategy in heart failure.

Affinity and activity profiling of unichiral 8-substituted 1,4-benzodioxane analogues of WB4101 reveals a potent and selective α1B-adrenoceptor antagonist

Unichiral 8-substituted analogues of 2-[(2-(2,6-dimethoxyphenoxy)ethyl)aminomethyl]-1,4-benzodioxane (WB4101) were synthesized and tested for binding affinity at cloned human α(1a)-, α(1b)-and α(1d)-adrenoreceptor (α(1a)-, α(1b)-and α(1d)-AR) and at native rat 5-HT(1A) receptor and for antagonist affinity at α(1A)-, α(1B)-and α(1D)-AR and at α(2A/D)-AR. Among the selected 8-substituents, namely fluorine, chlorine, methoxyl and hydroxyl, only the last caused significant decrease of α(1) binding affinity in comparison with the lead compound. Functional tests on the S isomers confirmed the detrimental effect of OH positioned in proximity to benzodioxane O(1). For the other three substituents (F, Cl, OMe), the α(1A) and the α(1D) antagonist affinities were generally lower than the α(1a) and α(1d) binding affinities, but not the α(1B) antagonist affinity, which was similar and sensibly higher compared to α(1b) binding affinity in the case of F and OMe respectively. This trend confers significant α(1B)-AR selectivity, in particular, to the 8-methoxy analogue of (S)-WB4101, a new potent (pA(2) 9.58) α(1B)-AR antagonist. The S enantiomers of all the tested compounds were proved to act as α(1)-AR inverse agonists in a vascular model.

Discovery of LASSBio-772, a 1,3-benzodioxole N-phenylpiperazine derivative with potent alpha 1A/D-adrenergic receptor blocking properties

We described herein the discovery of 1-(2-(benzo[d] [1,3]dioxol-6-yl)ethyl)-4-(2-methoxyphenyl) piperazine (LASSBio-772), as a novel potent and selective alpha 1A/1D adrenoceptor (AR) antagonist selected after screening of functionalized N-phenylpiperazine derivatives in phenylephrine-induced vasoconstriction of rabbit aorta rings. The affinity of LASSBio-772 for alpha 1A and alpha 1B AR subtypes was determined through displacement of [(3)H]prazosin binding. We obtained Ki values of 0.14 nM for the alpha 1A-AR, similar to that displayed by tamsulosin (K(i) = 0.13 nM) and 5.55 nM for the alpha 1B-AR, representing a 40-fold higher affinity for alpha 1A-AR. LASSBio-772 also presented high affinity (K(B) = 0.025 nM) for the alpha 1D-AR subtype in the functional rat aorta assay, showing to be equipotent to tamsulosin (K(B) = 0.017 nM).

Cardiovascular drug therapy in the elderly

Pharmacokinetic considerations in the elderly include absorption, bioavailablility, drug distribution, half-life, drug metabolism, and drug excretion. There are numerous physiologic changes with aging that affect pharmacodynamics with alterations in end-organ responsiveness. This article discusses use of cardiovascular drugs in the elderly including digoxin, diuretics, beta-adrenergic blockers, angiotensin-converting enzyme inhibitors, angiotensin-II receptor blockers, nitrates, calcium channel blockers, alpha-adrenergic blockers, antiarrhythmic drugs, lipid-lowering drugs, and anticoagulants. This article also discusses the adverse effects of cardiovascular drugs in the elderly, medications best to avoid in the elderly, and the prudent use of medications in the elderly.

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.

Association of alpha1A adrenergic receptor gene variants on chromosome 8p21 with human stage 2 hypertension

OBJECTIVE AND DESIGN

We previously reported a significant linkage between human chromosome 8p22 with essential hypertension and systolic blood pressure levels. On the basis of this, we used an efficient age, sex and area-matched case-control scheme to test the association of the polymorphisms in the human alpha1A adrenergic receptor (ADRA1A) gene, located on chromosome 8p21-p11.2, with essential hypertension in a northern Han Chinese population.

METHODS

Seven polymorphisms were identified by direct sequencing of genomic DNA derived from 48 randomly recruited hypertensive and 48 healthy subjects. They were also examined for association with essential hypertension in 480 stage 2 hypertensive individuals and their individually matched controls.

RESULTS

We observed significantly higher frequencies of the 347Arg allele and 2547G alleles in the cases compared with their controls (P = 0.04 and 0.007, respectively). McNemar's test revealed that carriers of 2547G alleles were at a greater risk of essential hypertension with an odds ratio of 3.00 [95% confidence interval (CI) 1.23-8.35]. We then performed a conditional logistic regression to adjust the effects of conventional risk factors, revealing an odds ratio of 2.84 for carriers of the 2547G allele (95% CI 1.15-6.99). With the haplotypic probabilities estimated using PHASE software, we performed haplotype trend regression analysis, showing a significant association between haplotype 7 and essential hypertension (P = 0.02), after adjustment for conventional risk factors.

CONCLUSIONS

Our findings suggest that the genetic variations in the ADRA1A gene are significantly associated with essential hypertension, and may play an important role in the development of essential hypertension in this Chinese population.

How to use calcium antagonists in hypertension: putting the JNC-VI guidelines into practice. Joint National Committee for the Prevention, Detection, Evaluation and Treatment of High Blood Pressure

The prevention and treatment of hypertension remain as major challenges for clinicians all over the world. The recently published Sixth Report of the Joint National Committee for the Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC-VI) uses evidence-based medicine in providing guidelines to aid clinicians in the prevention, detection and treatment of high blood pressure, including pharmacological approaches. Calcium antagonists are used widely for the treatment of hypertension, and JNC-VI focuses on specific situations where calcium antagonists could be considered as preferred treatments. There are a large number of calcium antagonists available, with a variety of pharmacodynamic and pharmacokinetic actions. Several sustained-release formulations of these drugs are also available. In terms of blood pressure control, calcium antagonists are more effective as antihypertensive treatments than beta-blockers, ACE inhibitors and angiotensin II receptor blockers in Black patients. The dihydropyridine calcium antagonists have been shown to reduce morbidity and mortality in elderly patients with isolated systolic hypertension. The rate-lowering calcium antagonists can be used as alternatives to beta-blockers in patients with coronary artery disease and hypertension. Calcium antagonists can be used as alternatives to ACE inhibitors in patients with hypertension and concomitant diabetes mellitus and/or renal disease. Some dihydropyridine calcium antagonists may be useful as alternatives to ACE inhibitors in patients with hypertension and systolic heart failure. Calcium antagonists appear to be extremely useful in patients with cyclosporin-induced hypertension, and in patients with hypertension and concomitant Raynaud's phenomenon and/or migraine. The rate-lowering agents can be used in patients with atrial tachyarrhythmias and hypertension. Clinicians should be aware of drug-drug interactions involving calcium antagonists, especially after the recent problems with mibefradil. Although retrospective studies have caused controversy regarding the safety of calcium antagonists in patients with hypertension, recent prospective studies have revealed no major safety concerns with these drugs.