Nitrate tolerance, rebound, and their clinical relevance in stable angina pectoris, unstable angina, and heart failure

Novel nitric oxide donors are coronary vasodilators that also bind to the papain-like protease of SARS-CoV-2

Several investigational nitric oxide donors were originally created to correct vascular endothelial dysfunction in cardiovascular diseases. These 48 compounds contain an urea-like moiety attached to the well-known NO donors isosorbide 2- and 5-mononitrate. CR-0305 and CR-0202 were synthesized and found to be nontoxic in the cell lines HMEC-1, A549/hACE2 and VeroE6. CR-0305 induced vasodilation in human coronary arteries ex vivo. Since NO can also have antiviral properties, a study of drug-protein interactions with SARS-CoV-2 was undertaken using in silico modeling. CR-0305 experimentally outperformed the other compounds, including CR-0202, in binding the catalytic site of SARS-CoV-2 papain-like protease (PLpro). PLpro is a primary target for therapeutic inhibition of SARS-CoV-2 as it mediates viral replication and modulates host innate immune responses. CR-0305 is predicted to sit firmly in the PLpro catalytic pocket as confirmed by molecular dynamics simulations, wherein stability of binding to the catalytic site of PLpro induces a conformational change in the BL2 loop to a more closed conformation as observed previously with GRL0617. Surface plasmon resonance was performed with CR-0305 and CR-0202 to characterize binding affinity to purified SARS-CoV-2 PLpro protein. CR-0305 and CR-0202 also inhibited SARS-CoV-2 infection compared to vehicle as measured by virus N protein staining with a specific antibody in A549-ACE2 and VeroE6 cells at 20 µM. CR-0305 is a coronary vasodilator that appears to bind to the catalytic site of the PLpro of SARS-CoV-2 while targeting delivery of antiviral NO to cells infected by SARS-CoV-2, suggesting multiple indications for future development.

Effectiveness and Safety of Acupoint Application of Guan Xin Su He Pill () for Patients with Chronic Stable Angina Pectoris: A Multi-Center, Randomized Controlled Trial

OBJECTIVE

To assess the clinical effectiveness of acupoint application (AP) of Guan Xin Su He Pill (, GXSHP) for patients with chronic stable angina pectoris (CSAP).

METHODS

This study was carried out in 3 local hospitals in Chengdu, China. After baseline evaluation, eligible patients were randomly assigned to the placebo application for acupoints (PAA) group or the herbal application for acupoints (HAA) group. Patients in the HAA group underwent AP with herbal powder, which was mainly GXSHP, and patients in the PAA group underwent AP with sham drugs. For each treatment session, unilateral acupoints including Neiguan (PC 6), Danzhong (RN 17), Xinshu (BL 15) and Jueyinshu (BL 14), were stimulated for both groups. AP was performed 3 times a week with a 2-day interval for 4 weeks. The primary outcome was the frequency of angina pectoris attacks per week, while the secondary outcomes included angina pain intensity measured by the Visual Analogue Scale (VAS), dose of rescue oral drugs (nitroglycerin), scores on the Seattle Angina Questionnaire (SAQ), Self-Rating Anxiety Scale scores (SAS) and Self-Rating Depression Scale scores (SDS). Clinical outcomes were measured at week 0, 4 and 8. The safety of AP of GXSHP treatment for CSAP were assessed.

RESULTS

A total of 121 patients were enrolled. Baseline characteristics were comparable across the 2 groups. After treatment, the angina attack numbers in the HAA group were significantly reduced from 11.00 to 4.81 (P<0.05). While, for PAA group, the angina frequency was not significantly improved (baseline 10.55; post-treatment 11.05). The HAA group had significantly fewer angina attacks than the PAA group (P<0.05). Pain intensity measured by VAS in HAA group was significantly reduced from 4.06 to 3.02 (P<0.05). While, for PAA group, the VAS was significantly increased (baseline 3.62; post-treatment 3.96; P<0.05). Clinical outcomes showed better improvement after treatment in the HAA group than in the PAA group in terms of oral administration of rescue drugs, SAS, SDS and SAQ scores (P<0.05). The adverse events were also reported.

CONCLUSION

AP of GXSHP is a safe and effective treatment for CSAP patients (Registration No. NCT02029118).

Compound salvia pellet might be more effective and safer for chronic stable angina pectoris compared with nitrates: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Chronic stable angina (CSA) resulted in a considerable burden for both individuals and the society. In this study we aimed to critically evaluate the effectiveness and safety of Compound salvia pellet compared with nitrates in the treatment of Chronic Stable Angina (CSA) pectoris, and to provide more credible evidence for clinical practice.

METHODS

A comprehensive and exhaustive search strategy was formulated to identify potential RCTs of compound salvia pellet for CSA in international and Chinese databases from their inception to July 4th, 2018. We also searched the bibliographies of relevant studies. Two reviewers independently assessed the quality of included trials by using Cochrane Risk of Bias Tool.

RESULTS

The literature search yielded 1849 citations and 51 RCTs (n = 4732) were included for meta-analysis after titles, abstracts and full text selection according to eligibility criteria. The pooled results suggested that compound salvia pellet was much more effective than nitrates in the improvement of angina symptoms (therapy = 4 weeks, RR = 1.23, 95%CI = [1.17, 1.30], P < .001, I = 0%; therapy = 4 weeks, RR = 1.13, 95%CI = [1.08, 1.17], P < .001, I = 45.6%), and ECG test (therapy = 4 weeks, RR = 1.24, 95%CI [1.14, 1.35], P < .001, I = 51.5%; and therapy > 4 weeks, RR = 1.30, 95%CI[1.20, 1.42], P < .001, I = 36.4%) in CSA. Compared with nitrates, the percentage of patients with adverse events significantly decreased when prescribed with compound salvia pellet (3.2% vs 17.0%).

CONCLUSION

Compound salvia pellet might be more effective on the improvement of angina symptoms, ECG test and with few adverse events compared with nitrates. While there are some limitations in this study, which may weaken the results, we believe the findings could provide useful information for stakeholders concerned with outcomes in patients with CSA. More rigorous RCTs with high quality are needed to confirm these findings.

Encapsulation of tDodSNO generates a photoactivated nitric oxide releasing nanoparticle for localized control of vasodilation and vascular hyperpermeability

We report the synthesis and characterization of a photoactive nitric oxide (NO) releasing nanoparticle (NP) by encapsulation of the NO donor tert-dodecane S-nitrosothiol (tDodSNO) into a co-polymer of styrene and maleic anhydride (SMA) to afford SMA-tDodSNO. Encapsulation did not affect tDodSNO's stability or NO release profile, but imparted water solubility and protection from degradation reactions with glutathione. Under photoactivation the NP acted as a potent NO donor, with photoactivation acting as a switch to induce localized vasodilation in aortic rings (EC₅₀^* 660 nM at 2700 W/m²) and cause vascular hyperpermeability in mesenteric beds (8-fold increase in dye uptake at 1 µM SMA-tDodSNO with 460 W/m² photoactivation). The NP was markedly superior as a photoactive NO donor in comparison to the S-nitrosothiols GSNO and SNAP, which are commonly used in experimental studies, as well as sodium nitroprusside, a clinically used vasodilator. Future development of this NP may find wide ranging therapeutic applications for treating cardiovascular disease and other disorders related to NO signaling, as well as enhancing macromolecular drug delivery to target organs through selective hyperpermeability. Supporting information describing the biophysical characterization of SMA-tDodSNO is supplied in an accompanying Data in Brief article (Alimoradi et al., doi: 10.1016/j.dib.2018.10.149).

The Role of Nitroglycerin and Other Nitrogen Oxides in Cardiovascular Therapeutics

The use of nitroglycerin in the treatment of angina pectoris began not long after its original synthesis in 1847. Since then, the discovery of nitric oxide as a biological effector and better understanding of its roles in vasodilation, cell permeability, platelet function, inflammation, and other vascular processes have advanced our knowledge of the hemodynamic (mostly mediated through vasodilation of capacitance and conductance arteries) and nonhemodynamic effects of organic nitrate therapy, via both nitric oxide-dependent and -independent mechanisms. Nitrates are rapidly absorbed from mucous membranes, the gastrointestinal tract, and the skin; thus, nitroglycerin is available in a number of preparations for delivery via several routes: oral tablets, sublingual tablets, buccal tablets, sublingual spray, transdermal ointment, and transdermal patch, as well as intravenous formulations. Organic nitrates are commonly used in the treatment of cardiovascular disease, but clinical data limit their use mostly to the treatment of angina. They are also used in the treatment of subsets of patients with heart failure and pulmonary hypertension. One major limitation of the use of nitrates is the development of tolerance. Although several agents have been studied for use in the prevention of nitrate tolerance, none are currently recommended owing to a paucity of supportive clinical data. Only 1 method of preventing nitrate tolerance remains widely accepted: the use of a dosing strategy that provides an interval of no or low nitrate exposure during each 24-h period. Nitric oxide's important role in several cardiovascular disease mechanisms continues to drive research toward finding novel ways to affect both endogenous and exogenous sources of this key molecular mediator.

An Overview of Meta-Analyses of Danhong Injection for Unstable Angina

Objective. To systematically collect evidence and evaluate the effects of Danhong injection (DHI) for unstable angina (UA). Methods. A comprehensive search was conducted in seven electronic databases up to January 2015. The methodological and reporting quality of included studies was assessed by using AMSTAR and PRISMA. Result. Five articles were included. The conclusions suggest that DHI plus conventional medicine treatment was effective for UA pectoris treatment, could alleviate symptoms of angina and ameliorate electrocardiograms. Flaws of the original studies and systematic reviews weaken the strength of evidence. Limitations of the methodology quality include performing an incomprehensive literature search, lacking detailed characteristics, ignoring clinical heterogeneity, and not assessing publication bias and other forms of bias. The flaws of reporting systematic reviews included the following: not providing a structured summary, no standardized search strategy. For the pooled findings, researchers took statistical heterogeneity into consideration, but clinical and methodology heterogeneity were ignored. Conclusion. DHI plus conventional medicine treatment generally appears to be effective for UA treatment. However, the evidence is not hard enough due to methodological flaws in original clinical trials and systematic reviews. Furthermore, rigorous designed randomized controlled trials are also needed. The methodology and reporting quality of systematic reviews should be improved.

Organic nitrates: past, present and future

Nitric oxide (NO) is one of the most important vasodilator molecules produced by the endothelium. It has already been established that NO/cGMP signaling pathway deficiencies are involved in the pathophysiological mechanisms of many cardiovascular diseases. In this context, the development of NO-releasing drugs for therapeutic use appears to be an effective alternative to replace the deficient endogenous NO and mimic the role of this molecule in the body. Organic nitrates represent the oldest class of NO donors that have been clinically used. Considering that tolerance can occur when these drugs are applied chronically, the search for new compounds of this class with lower tolerance potential is increasing. Here, we briefly discuss the mechanisms involved in nitrate tolerance and highlight some achievements from our group in the development of new organic nitrates and their preclinical application in cardiovascular disorders.

Challenges with nitrate therapy and nitrate tolerance: prevalence, prevention, and clinical relevance

Nitrate therapy has been an effective treatment for ischemic heart disease for over 100 years. The anti-ischemic and exercise-promoting benefits of sublingually administered nitrates are well established. Nitroglycerin is indicated for the relief of an established attack of angina and for prophylactic use, but its effects are short lived. In an effort to increase the duration of beneficial effects, long-acting orally administered and topical applications of nitrates have been developed; however, following their continued or frequent daily use, patients soon develop tolerance to these long-acting nitrate preparations. Once tolerance develops, patients begin losing the protective effects of the long-acting nitrate therapy. By providing a nitrate-free interval, or declining nitrate levels at night, one can overcome or reduce the development of tolerance, but cannot provide 24-h anti-anginal and anti-ischemic protection. In addition, patients may be vulnerable to occurrence of rebound angina and myocardial ischemia during periods of absent nitrate levels at night and early hours of the morning, and worsening of exercise capacity prior to the morning dose of the medication. This has been a concern with nitroglycerin patches but not with oral formulations of isosorbide-5 mononitrates, and has not been adequately studied with isosorbide dinitrate. This paper describes problems associated with nitrate tolerance, reviews mechanisms by which nitrate tolerance and loss of efficacy develop, and presents strategies to avoid nitrate tolerance and maintain efficacy when using long-acting nitrate formulations.

Sanqi panax notoginseng injection for angina pectoris

Objective. To evaluate the clinical curative effects of SPN injection on AP. Methods. Six databases were systematically searched including Cochrane Central, PubMed, EMBASE, CBM, Chinese National Knowledge Infrastructure (CNKI), and VIP to identify randomized controlled trials (RCTs). We assessed the quality of included studies, extracted valid data, and undertook meta-analysis following the steps of systematic review recommended by the Cochrane group. Results. Ten moderate-to-low quality randomized controlled trials involving 969 patients were included. There was no evidence that SPN alone had better or worse effects than conventional drugs on improving clinical symptoms (RR 1.09, 95% CI 0.85 to 1.39) and ECG (RR 1.17, 95% CI 0.84 to 1.63). However, there was an evidence that SPN combined with western medications was a better treatment option than conventional drugs alone in improving clinical symptoms (RR 1.28, 95% CI 1.19 to 1.33) and ECG (RR 1.27, 95% CI 1.12 to 1.45). No serious adverse effects were reported. Conclusion. Compared with conventional treatment, SPN may show the potential of optimizing symptomatic outcomes. As a kind of alternative and complementary medicine, SPN may provide another choice for AP patients and further large-scale high-quality trials are needed to confirm this efficacy.

Nitrates and bone turnover (NABT) - trial to select the best nitrate preparation: study protocol for a randomized controlled trial

Background

Organic nitrates uncouple bone turnover, improve bone mineral density, and improve trabecular and cortical components of bone. These changes in turnover, strength and geometry may translate into an important reduction in fractures. However, before proceeding with a large fracture trial, there is a need to identify the nitrate formulation that has both the greatest efficacy (with regards to bone turnover markers) and gives the fewest headaches. Ascertaining which nitrate formulation this may be is the purpose of the current study.

Methods and design

This will be an open-label randomized, controlled trial conducted at Women’s College Hospital comparing five formulations of nitrates for their effects on bone turnover markers and headache. We will recruit postmenopausal women age 50 years or older with no contraindications to nitroglycerin. Our trial will consist of a run-in phase and a treatment phase. We will enroll 420 women in the run-in phase, each to receive all of the 5 potential treatments in random order for 2 days, each with a 2-day washout period between treatments. Those who tolerate all formulations will enter the 12-week treatment phase and be randomly assigned to one of five groups: 0.3 mg sublingual nitroglycerin tablet, 0.6 mg of the sublingual tablet, a 20 mg tablet of isosorbide mononitrate, a 160 mg nitroglycerin transdermal patch (used for 8 h), and 15 mg of nitroglycerin ointment as used in a previous trial by our group. We will continue enrolment until we have randomized 210 women or 35 women per group. Concentrations of bone formation (bone-specific alkaline phosphatase and procollagen type I N-terminal propeptide) and bone resorption (C-telopeptides of collagen crosslinks and N-terminal crosslinks of collagen) agents will be measured in samples taken at study entry (the start of the run in phase) and 12 weeks. Subjects will record the frequency and severity of headaches daily during the run-in phase and then monthly after that. We will use the ‘multiple comparisons with the best’ approach for data analyses, as this strategy allows practical considerations of ease of use and tolerability to guide selection of the preparation for future studies.

Discussion

Data from this protocol will be used to develop a randomized, controlled trial of nitrates to prevent osteoporotic fractures.

Trial registration

ClinicalTrials.gov Identifier: NCT01387672. Controlled-Trials.com: ISRCTN08860742.

Acupuncture therapy for angina pectoris: a systematic review

OBJECTIVE

To assess the effectiveness and safety of acupuncture therapy for angina pectoris.

METHODS

Randomized controlled trials (RCTs) concerned with acupuncture treatment of angina pectoris were identified by searching Academic Source Premier, MEDLINE, Science Citation Index Expanded, and three Chinese databases (China biology medicine database, China national knowledge infrastructure, and VIP database for Chinese technical periodicals). The valid data were extracted in accordance with our inclusion and exclusion criteria. The main outcomes of the included studies were synthesized using Revman 5.1.

RESULTS

Twenty-one articles on 16 individual studies were included and evaluated as having high or moderate risk of bias according to the standards of the Cochrane Collaboration. Meta-analysis indicated that acupuncture combined with conventional drugs (ACCD) was superior to conventional drugs alone in reducing the incidence of acute myocardial infarction (AMI) [OR = 0.18, 95% CI (0.04, 0.84), P = 0.03]. Moreover, ACCD was superior to conventional drugs in the relief of angina symptoms [OR = 4.23, 95% CI (2.73, 6.56), P < 0.00001], and improvement of electrocardiography (ECG) [OR = 2.61, 95% CI (1.83, 3.73), P < 0.00001]. Acupuncture by itself was also superior to conventional drugs for angina symptoms [OR = 3.59, 95% CI (1.76,7.92), P = 0.0004] and ECG improvement [OR = 3.07, 95% CI (1.54, 6.10), P = 0.001]. ACCD was superior to conventional drugs in shortening the time to onset of angina relief [WMD = -1.40, 95% CI (-1.65, -1.15), P < 0.00001]. However, the time to onset was significantly longer for acupuncture treatment than for conventional treatment alone [WMD = 2.43, 95% CI (1.63, 3.23), P < 0.000 01].

CONCLUSION

ACCD reduced the occurrence of AMI, and both acupuncture and ACCD relieved angina symptoms and improved ECG. However, compared with conventional treatment, acupuncture showed a longer delay before its onset of action. This indicates that acupuncture is not suitable for emergency treatment of heart attack. Owing to the poor quality of the current evidence, the findings of this systematic review need to be verified by more RCTs to enhance statistical power.

[Which future in cardiovascular therapy for nitric oxide and its derivatives?]

Nitric oxide (NO) is involved in the regulation of several physiological processes such as vascular homeostasis. Exogenous NO supply offers major therapeutic interest, especially in the treatment of coronary artery disease, ischemic syndromes and other cardiovascular pathologies. Nevertheless, the administration of NO itself is limited by its short half-life. NO prodrugs have been marketed for decades, e.g. organic nitrates for angina pectoris. These prodrugs display undeniable advantages such as angina crisis relief and preconditioning effect. Nevertheless, they suffer from several drawbacks: toxicity, tolerance, endothelial dysfunction exacerbation. These negative effects are related to massive production of reactive species derived from oxygen or nitrogen, which trigger oxidative and nitrosative stress. New NO donors are under development to overcome those disadvantages, among which the S-nitrosothiols family seems especially promising.

Organic nitrates for osteoporosis: an update

The number of osteoporotic fractures is increasing worldwide as populations age. An inexpensive and widely available treatment is necessary to alleviate this increase in fractures. Current treatments decrease fractures at trabecular bone sites (spine) but have limited effects at cortical sites (hip, legs, forearm and upper arm)-the most common sites of osteoporotic fracture. Treatments are also limited by costs, side effects and lack of availability. Nitric oxide (NO) is a novel agent that has the potential to influence cortical bone, is inexpensive, widely available and has limited side effects. In this review, we will evaluate the in vitro and in vivo data that support the concept that NO is important in bone cell function, review the observational, case control and randomized trial data on organic nitrates and the effects of these agents on bone turnover, geometry and strength.

Organic nitrate maintains bone marrow blood perfusion in ovariectomized female rats: a dynamic, contrast-enhanced magnetic resonance imaging (MRI) study

This study investigated the effects of nitrate on bone mineral density (BMD) and bone marrow perfusion in ovariectomized (OVX) female rats, and also the effects of nitrate on in vitro osteoblastic activity and osteoclastic differentiation of murine monocyte/macrophage RAW 264.7 cells. Female Sprague–Dawley rats were divided into OVX + nitrate group (isosorbide-5-mononitrate, ISM, 150 mg/kg/ day b.i.d), OVX + vehicle group, and control group. Lumbar spine CT bone densitometry and perfusion MRI were performed on the rats at baseline and week 8 post-OVX. The OVX rats’ BMD decreased by 22.5% ± 5.7% at week 8 (p < 0.001); while the OVX + ISM rats’ BMD decreased by 13.1% ± 2.7% (p < 0.001). The BMD loss difference between the two groups of rats was significant (p = 0.018). The OVX rats’ lumbar vertebral perfusion MRI maximum enhancement (Emax) decreased by 10.3% ± 5.0% at week 8 (p < 0.005), while in OVX + ISM rats, the Emax increased by 5.5% ± 6.9% (p > 0.05). The proliferation of osteoblast-like UMR-106 cells increased significantly with ISM treatment at 0.78 µM to 50 μM. Treatment of UMR-106 cells with ISM also stimulated the BrdU uptake. After the RAW 264.7 cells were co-treated with osteoclastogenesis inducer RANKL and 6.25 μM ~ 100 μM of ISM for 3 days, a trend of dose-dependent increase of osteoclast number was noted.

Nitrates as an integral part of optimal medical therapy and cardiac rehabilitation for stable angina: review of current concepts and therapeutics

The goals of optimal medical therapy in patients with stable angina pectoris are to reduce the risk of cardiovascular mortality and future cardiovascular events, improve exercise capacity, and enhance quality of life. Whereas myocardial revascularization is frequently employed in the management of patients with stable angina, a variety of pharmacologic interventions are recommended as part of optimal medical management. The use of short- and rapidly-acting nitrates (eg, sublingual nitroglycerin spray and tablets) is at the core of the therapeutic armamentarium and should be integrated into optimal medical therapy for stable angina along with exercise therapy. The potential clinical implications from these observations are that prophylactic sublingual nitrates, when combined with cardiac rehabilitation, may allow the patient with angina to exercise to a greater functional capacity than without sublingual nitrates.

Nitric oxide donors for the treatment of osteoporosis

The number of osteoporotic fractures is increasing worldwide as populations age. An inexpensive and widely available treatment is necessary to alleviate this increase in fractures. Current treatments decrease fractures at trabecular bone sites (spine) but have limited effects at cortical sites (hip, legs, forearm, and upper arm)-the most common sites of osteoporotic fracture. Treatments are also limited by costs, side effects, and lack of availability. Nitric oxide is a novel agent that has the potential to influence cortical bone, is inexpensive, is widely available, and has limited side effects. In this review we evaluate the in vitro and in vivo data which support the concept that nitric oxide is important in bone cell function, review the observational and case-control studies reporting on subjects taking organic nitrates that act as nitric oxide donors, and review the effects of nitrates on bone mineral density measurements and fracture risk.

Hypoxia inducible factor-1 protects against nitrate tolerance and stunning in rabbit cardiac myocytes

PURPOSE

We tested whether upregulation of hypoxia inducible factor-1 (HIF-1) would restore the blunted effects of natriuretic peptides and nitric oxide caused by chronic nitrate exposure and stunning in cardiac myocytes.

METHODS

HIF-1alpha was increased with deferoxamine (150 mg/kg for 2 days). Nitrate tolerance was induced by a chronic nitroglycerin patch (0.3 mg/h for 5 days). We used freshly isolated rabbit ventricular myocytes. Half the myocytes were subjected to simulated ischemia [15 min 95% N(2)-5% CO(2)] and reperfusion [reoxygenation] to produce stunning. Cell function was measured utilizing a video-edge detector. Shortening was examined at baseline and after brain natriuretic peptide (BNP, 10(-8), 10(-7) M) or S-nitroso-N-acetyl-penicillamine (SNAP, 10(-6), 10(-5) M) followed by KT5823 (cyclic GMP protein kinase inhibitor, 10(-6) M). We also measured cyclic GMP protein kinase protein levels and kinase activity.

RESULTS

In control, BNP (-29%) reduced percent shortening, while KT5823 partially restored function. Deferoxamine treated control myocytes responded similarly. In patched nonstunned myocytes, BNP (-12%) reduced shortening less and KT5823 did not increase function. However, deferoxamine restored the blunted effects of BNP (-21%) and KT5823. In stunned myocytes, BNP (-11%) reduced shortening less and KT5823 did not affect function. Deferoxamine increased the effects of BNP (-27%) and KT5823 in stunning. Patch combined with stunning also similarly blunted the effects of BNP (-12%) and KT5823. Deferoxamine improved the effects of BNP (-22%) and KT5823. Similar results were observed after SNAP. Stunning reduced cyclic GMP protein kinase activity and deferoxamine restored activity. Deferoxamine had no effect on kinase activity in nitrate tolerance.

CONCLUSION

We found that upregulation of HIF-1 could protect isolated cardiac myocytes against nitrate tolerance through a cyclic GMP protein kinase-independent mechanism and through a kinase-dependent mechanism in stunning.

Recent advances in the management of chronic stable angina II. Anti-ischemic therapy, options for refractory angina, risk factor reduction, and revascularization

The objectives in treating angina are relief of pain and prevention of disease progression through risk reduction. Mechanisms, indications, clinical forms, doses, and side effects of the traditional antianginal agents - nitrates, β-blockers, and calcium channel blockers - are reviewed. A number of patients have contraindications or remain unrelieved from anginal discomfort with these drugs. Among newer alternatives, ranolazine, recently approved in the United States, indirectly prevents the intracellular calcium overload involved in cardiac ischemia and is a welcome addition to available treatments. None, however, are disease-modifying agents. Two options for refractory angina, enhanced external counterpulsation and spinal cord stimulation (SCS), are presented in detail. They are both well-studied and are effective means of treating at least some patients with this perplexing form of angina. Traditional modifiable risk factors for coronary artery disease (CAD) - smoking, hypertension, dyslipidemia, diabetes, and obesity - account for most of the population-attributable risk. Individual therapy of high-risk patients differs from population-wide efforts to prevent risk factors from appearing or reducing their severity, in order to lower the national burden of disease. Current American College of Cardiology/American Heart Association guidelines to lower risk in patients with chronic angina are reviewed. The Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial showed that in patients with stable angina, optimal medical therapy alone and percutaneous coronary intervention (PCI) with medical therapy were equal in preventing myocardial infarction and death. The integration of COURAGE results into current practice is discussed. For patients who are unstable, with very high risk, with left main coronary artery lesions, in whom medical therapy fails, and in those with acute coronary syndromes, PCI is indicated. Asymptomatic patients with CAD and those with stable angina may defer intervention without additional risk to see if they will improve on optimum medical therapy. For many patients, coronary artery bypass surgery offers the best opportunity for relieving angina, reducing the need for additional revascularization procedures and improving survival. Optimal medical therapy, percutaneous coronary intervention, and surgery are not competing therapies, but are complementary and form a continuum, each filling an important evidence-based need in modern comprehensive management.

The usefulness of chronic heart failure treatments in chronic cardiac graft failure

Following cardiac transplantation, registry data has demonstrated a gradual improvement in survival over the last several decades, which is testament to continual improvement in aftercare strategy. However, a significant number of patients will eventually develop a new syndrome of chronic heart failure, owing to the multitude of physiological processes that occur after transplantation. This condition, referred to as chronic graft failure (CGF) should be regarded as a unique illness rather than one that is simply analogous with chronic heart failure. In particular, the unique pathophysiological (and pharmacological) environment in the setting of CGF presents a challenging situation to the transplant physician. There is uncertainty over which treatments to offer given a paucity of clinical trial data to support the use of standard heart failure treatments in CGF. In this review, we discuss which chronic heart failure treatments could be considered in the setting of CGF based on their mechanisms of action, benefits within the native heart failure setting, and the relevant issues within the posttransplant environment.

Exploiting cGMP-based therapies for the prevention of left ventricular hypertrophy: NO* and beyond

Left ventricular hypertrophy (LVH), an increased left ventricular (LV) mass, is common to many cardiovascular disorders, initially developing as an adaptive response to maintain myocardial function. In the longer term, this LV remodelling becomes maladaptive, with progressive decline in LV contractility and diastolic function. Indeed LVH is recognised as an important blood-pressure independent predictor of cardiovascular morbidity and mortality. The clinical efficacy of current treatments for LVH is reduced, however, by their tendency to slow disease progression rather than induce its reversal, and thus the development of new therapies for LVH is paramount. The signalling molecule cyclic guanosine-3',5'-monophosphate (cGMP), well-recognised for its role in regulating vascular tone, is now being increasingly identified as an important anti-hypertrophic mediator. This review is focused on the various means by which cGMP can be stimulated in the heart, such as via the natriuretic peptides, to exert anti-hypertrophic actions. In particular we address the limitations of traditional nitric oxide (NO*) donors in the face of the potential therapeutic advantages offered by novel alternatives; NO* siblings, ligands of the cGMP-generating enzymes, soluble (sGC) and particulate guanylyl cyclases (pGC), and phosphodiesterase inhibitors. Further impact of cGMP within the cardiovascular system is also discussed with a view to representing cGMP-based therapies as innovative pharmacotherapy, alone or concurrent with standard care, for the management of LVH.

Nitrate use and changes in bone mineral density: the Canadian Multicentre Osteoporosis Study

Nitrates may have beneficial effects on bone. To determine if nitrates were associated with increased bone mineral density (BMD), we conducted a secondary analysis using data from subjects in a prospective study. Subjects reporting nitrate use had increased BMD compared with non-users, confirming that nitrates have positive BMD effects in women and men.

INTRODUCTION

Prior studies suggest positive associations between nitrates and bone.

METHODS

We used linear regression models, stratified by gender and adjusted for age, weight, and baseline differences, to determine the association between daily nitrate use and BMD among subjects participating in the Canadian Multicentre Osteoporosis Study. All results are reported as annualised percent change in BMD at the hip and spine among nitrate users compared to non-users.

RESULTS

We included 1,419 men (71 reported daily nitrate use) and 2,587 women (97 reported daily nitrate use). Male non-users had decreased hip BMD (-1.3%; 95% confidence interval [95%CI] = -1.6 to -1.1) and increased spine BMD (2.8%; 95%CI = 2.5 to 3.1). Male nitrate users had increased hip BMD (1.4%; 95%CI = 0.1 to 2.8) and spine BMD (4.5%; 95%CI = 3.2 to 5.7). Among women, non-users had decreased hip BMD (-1.9; 95%CI = -2.1 to -1.7) and increased spine BMD (2.1%; 95%CI = 1.9 to 2.4) whilst users had an increase in hip BMD (2.0%; 95%CI = 1.2 to 2.8) and spine BMD (4.1%; 95%CI = 3.4 to 4.9).

CONCLUSION

Nitrate use is associated with increased BMD at the hip and spine in men and women.

The enigma of nitroglycerin bioactivation and nitrate tolerance: news, views and troubles

Nitroglycerin (glyceryl trinitrate; GTN) is the most prominent representative of the organic nitrates or nitrovasodilators, a class of compounds that have been used clinically since the late nineteenth century for the treatment of coronary artery disease (angina pectoris), congestive heart failure and myocardial infarction. Medline lists more than 15 000 publications on GTN and other organic nitrates, but the mode of action of these drugs is still largely a mystery. In the first part of this article, we give an overview on the molecular mechanisms of GTN biotransformation resulting in vascular cyclic GMP accumulation and vasodilation with focus on the role of mitochondrial aldehyde dehydrogenase (ALDH2) and the link between the ALDH2 reaction and activation of vascular soluble guanylate cyclase (sGC). In particular, we address the identity of the bioactive species that activates sGC and the potential involvement of nitrite as an intermediate, describe our recent findings suggesting that ALDH2 catalyses direct 3-electron reduction of GTN to NO and discuss possible reaction mechanisms. In the second part, we discuss contingent processes leading to markedly reduced sensitivity of blood vessels to GTN, referred to as vascular nitrate tolerance. Again, we focus on ALDH2 and describe the current controversy on the role of ALDH2 inactivation in tolerance development. Finally, we emphasize some of the most intriguing, in our opinion, unresolved puzzles of GTN pharmacology that urgently need to be addressed in future studies.

Side effects of using nitrates to treat heart failure and the acute coronary syndromes, unstable angina and acute myocardial infarction

Nitrates are potent venous dilators and anti-ischemic agents. They are widely used for the relief of chest pain and pulmonary congestion in patients with acute coronary syndromes and heart failure. Nitrates, however, do not reduce mortality in patients with acute coronary syndromes. Combination of nitrates and hydralazine when given in addition to beta-blockers and angiotensin-converting enzyme (ACE) inhibitors reduce mortality and heart failure hospitalizations in patients with heart failure due to left ventricular systolic dysfunction who are of African-American origin. Side effects during nitrate therapy are common but are less well described in the literature compared with the reported side effects in patients with stable angina pectoris. The reported incidence of side effects varies highly among different studies and among various disease states. Headache is the most commonly reported side effect with an incidence of 12% in acute heart failure, 41-73% in chronic heart failure, 3-19% in unstable angina and 2-26% in acute myocardial infarction. The reported incidence of hypotension also differs: 5-10% in acute heart failure, 20% in chronic heart failure, 9% in unstable angina and < 1-48% in acute myocardial infarction, with the incidence being much higher with concomitant nitrate therapy plus angiotensin-converting enzyme inhibitors. Reported incidence of dizziness is as low as 1% in patients with acute myocardial infarction to as high as 29% in patients with heart failure. Severe headaches and/or symptomatic hypotension may necessitate discontinuation of nitrate therapy. Severe life threatening hypotension or even death may occur when nitrates are used in patients with acute inferior myocardial infarction associated with right ventricular dysfunction or infarction, or with concomitant use of phosphodiesterase-5 inhibitors or N-acetylcysteine. Despite the disturbing observational reports in the literature that continuous and prolonged use of nitrates may lead to increased mortality and recurrent myocardial infarction in patients with stable coronary artery disease, no such adverse effects of nitrates have been reported in the large randomized trials in patients with acute myocardial infarction or chronic heart failure.

Review of current and investigational pharmacologic agents for acute heart failure syndromes

Acute heart failure syndromes (AHFS) are a major public health problem and present a therapeutic challenge to clinicians. Commonly used agents in the treatment of AHFS include diuretics, vasodilators (eg, nitroglycerin, nitroprusside, nesiritide), and inotropes (eg, dobutamine, dopamine, milrinone). Patients admitted to hospital with AHFS and low cardiac output state (AHFS/LO) represent a subgroup with very high inhospital and postdischarge mortality rates. Most of these patients require intravenous inotropic therapy. However, the use of current intravenous inotropes has been associated with risk for hypotension, atrial and ventricular arrhythmias, and possibly increased postdischarge mortality, particularly in those with coronary artery disease. Consequently, there is an unmet need for new agents to safely improve cardiac performance (contractility and/or active relaxation) in this patient population. This article reviews a selection of current and investigational agents for the treatment of AHFS, with a main focus on the high-risk patient population with AHFS/LO.

The effects of organic nitrates on osteoporosis: a randomized controlled trial [ISRCTN94484747]

Background

Osteoporotic fractures are common and are associated with increased morbidity, mortality and health care costs. The most effective way to moderate increases in health care costs and the sickness and premature death associated with osteoporotic fractures, is to prevent osteoporosis. Several lines of evidence suggest that nitrates, drugs typically prescribed for the treatment of angina, may be effective in preventing postmenopausal osteoporosis.

Methods

We have designed a multicentre randomized controlled trial to determine the effects of nitrates on bone. The trial consists of two studies. The objective of the first study is to determine whether isosorbide mononitrate at 20 mg/day or nitroglycerin ointment at 15 mg/day leads to fewer headaches. The nitrate that is best tolerated will be used in a second study with one main objective: To determine if postmenopausal women with a T-score at the lumbar spine (L1 to L4) between 0 and -2.0 randomized to two years of treatment with intermittent nitrates have a greater increase in spine bone mineral density as compared to women randomized to placebo.

We hypothesize that: 1. Women will report fewer headaches when they are randomized to intermittent nitroglycerin ointment at 15 mg/day compared to intermittent oral isosorbide mononitrate at 20 mg/day, and, 2. After two years, women randomized to intermittent nitrates will have a greater percent increase in lumbar spine bone mineral density compared with women randomized to placebo.

Discussion

We have completed our pilot study and found that transdermal nitroglycerin was associated with fewer headaches than oral isosorbide mononitrate. We are currently recruiting patients for our second main study.

Progressive left ventricular hypertrophy after withdrawal of long-term ACE inhibition following experimental myocardial infarction

BACKGROUND

Although discontinuation of chronic ACE inhibitor (ACEi) therapy after myocardial infarction (MI) is common in clinical practice, some clinical studies reported an increased incidence of ischemia-related events after withdrawal. To further address this issue, we assessed hemodynamic, neurohormonal and vascular consequences of withdrawing long-term ACEi treatment after experimental MI.

METHODS

Rats were subjected to coronary ligation to induce MI, and received quinapril (15 mg/kg/day) from 2 weeks to 14 months post-MI. Subsequently, surviving rats were randomized to sacrifice at 0, 4, and 6 weeks after ACEi withdrawal. Rats were studied for signs of heart failure, hemodynamics and cardiac function, neurohormones, and vascular edothelial function.

RESULTS

After discontinuation of ACEi treatment, plasma aldosterone levels increased between 0-4 weeks without further increment thereafter, suggesting persistent RAAS activation. Acetylcholine-induced aortic relaxation was impaired at 4 and 6 weeks, indicating rapid and sustained development of endothelial vasodilator dysfunction after withdrawal. Moreover, 24% of the rats developed heart failure signs (edema, dyspnea), and 3 rats died, all within 4 weeks after withdrawal. Significantly increased N-ANP levels and lung weights at 4, but not at 6 weeks suggest a transient volume overload. Finally, LV/body weight ratios significantly increased between 0-4 as well as 4-6 weeks, indicating progressive LV hypertrophy.

CONCLUSIONS

The observed alterations after withdrawing long-term post-MI quinapril treatment in the present study may account for an increased risk for ischemic events. Thus, our findings highlight the potentially harmful effects associated with abrupt discontinuation of long-term post-MI ACE inhibition, and imply careful clinical consideration in this matter.

Nitroglycerin-patch induced tolerance is associated with reduced ability of nitroglycerin to increase exhaled nitric oxide

Nitroglycerin (GTN), used in the treatment of ischemic heart disease, acts through the liberation of nitric oxide (NO). However, its clinical use is limited due to tolerance development. Expired NO was used as an indicator of GTN-bioactivation and was measured together with plasma nitrite and mean arterial pressure (MAP) during GTN indicator infusions. The model was applied in rabbits subjected to various time periods of low-dose GTN pretreatment by patch application for 1, 24 and 72 h. Pretreatment with GTN-patch resulted in significant attenuation of expired NO from the GTN indicator infusion in the 24 h and 72 h pretreatment groups compared to placebo (72 h). Dose-response curves with increasing GTN infusions after 24 h GTN-patch pretreatment revealed a significant attenuation of the MAP decrease compared to placebo. GTN-induced changes in plasma nitrite correlated to increases in expired NO and decreases in MAP. This indicates that expired NO could serve as an indicator of NO generation from GTN in the vascular system. We conclude that GTN tolerance is associated with reduced capacity to generate NO from GTN. Care should be taken in using MAP-reduction to evaluate tolerance since high indicator doses could liberate sufficient amounts of NO to elicit maximal MAP decrease even in tolerant animals.

WITHDRAWAL OF INTRAVENOUS GLYCERYL TRINITRATE: ABSENCE OF REBOUND PHENOMENA WITH TRANSITION TO ORAL ISOSORBIDE DINITRATE

1. Glyceryl trinitrate (GTN) is frequently infused intravenously as a component of the management of acute coronary syndromes (ACS). Abrupt cessation of GTN infusion after periods of more than 24 h administration often induces rebound vasoconstriction reflecting 'pseudotolerance'; this is also the basis of the 'zero hour phenomenon' during chronic nitrate therapy. The efficacy of oral nitrate regimens to prevent vasoconstriction following cessation of intravenous GTN has not been previously examined. Therefore, we investigated the effects of transition from intravenous GTN to oral isosorbide dinitrate (ISDN) on a parameter of apparent arterial stiffness in patients with ACS. 2. The effects of GTN infusion at 5 microg/min on augmentation index (AIx) were quantified in patients (n = 10) with stable angina pectoris in order to establish the magnitude of effect on apparent arterial stiffness. 3. This infusion rate of GTN reduced AIx from 23 +/- 10% (SD) to 3 +/- 14% (SD) (P < 0.01). The effect of transition from GTN infusion of greater than 24 h duration to ISDN (10 mg tds) were examined in patients (n = 16) with ACS (unstable angina/non-Q-wave myocardial infarction). No patient developed recurrent angina during the 24 h following cessation of GTN infusion. The level of AIx was 8 +/- 4% (SD) prior to GTN cessation and fell to 5 +/- 6% (SD) on ISDN (P = 0.05). 4. Thus, in patients treated for ACS, transition from intravenous GTN to low dose oral ISDN is associated with an incremental vasodilatation and no evidence of 'rebound' ischaemia.

Isosorbide mononitrate increases bone formation and decreases bone resorption in postmenopausal women: a randomized trial

NO regulates bone remodeling in cellular and animal models. We examined the effect of administering ISMO, a NO donor, on bone turnover in 144 postmenopausal women. After 3 months, women randomized to ISMO had a greater decrease in bone resorption and a greater increase in bone formation compared with placebo. NO donors may prevent postmenopausal bone loss.

INTRODUCTION

NO both stimulates bone formation and inhibits bone resorption in vitro. NO donors (nitrates) are inexpensive and widely available, but their value for postmenopausal osteoporosis has never been evaluated in a randomized trial.

MATERIALS AND METHODS

We randomly assigned 144 healthy postmenopausal women with a hip BMD T score between 0 and -2.5 to 5 or 20 mg/day of isosorbide mononitrate (ISMO) or placebo for 12 weeks. We measured urine N-telopeptide (NTx), a marker of bone resorption, and serum bone-specific alkaline phosphatase (BSALP), a marker of bone formation. Markers were measured immediately before randomization and after 12 weeks of treatment. We calculated the percent change in NTx and BSALP for each of the treatment groups (placebo, 5 mg ISMO, and 20 mg ISMO). Our primary outcome was the percent change in NTx and BSALP in the 5- and 20-mg ISMO groups compared with placebo.

RESULTS AND CONCLUSIONS

Compared with women randomized to placebo, women randomized to 20 mg of ISMO had a 45.4% decrease in NTx (95% CI, 25.8-64.9) and a 23.3% increase (95% CI, 8.9-37.8) in BSALP. Women randomized to 5 mg of ISMO had a 36.3% decrease in NTx (95% CI, 14.8-57.8) and a 15.9% increase in BSALP (95% CI, 1.1-30.7). ISMO decreases bone resorption and increases bone formation. These findings suggest that nitrates may be useful for the prevention of postmenopausal osteoporosis.

Effect of nitric oxide donor nitroglycerin on bone mineral density in a rat model of estrogen deficiency-induced osteopenia

Nitric oxide (NO) may modulate estrogen's anabolic effects on bone homeostasis by restraining osteoclast-mediated bone resorption and stimulation of osteoblast activity. Accordingly, NO donated by organic nitrates, including nitroglycerin, is thought to protect against bone loss associated with estrogen deficiency. In this study, we have explored this phenomenon. Thirty-two 12-week-old female Wistar rats were divided into four groups prior to bilateral ovariectomy or a sham operation. The ovariectomised rats received (1). vehicle control (OVX control), (2). 17-beta-estradiol (OVX+E2), or (3). transdermal nitroglycerin (OVX+NG) for 4 weeks. Femoral and tibial bone mineral density (BMD), serum alkaline phosphatase and urine deoxypyridinoline and NO metabolites were analysed at the end of the study period together with failure torque and torsional rigidity of the tibiae and cellular localisation of the NO-synthase (NOS) isoforms. In OVX+E2 group, proximal and distal femoral and proximal tibial BMD exceeded that of the Sham controls. Nitroglycerin prevented BMD loss at these three sites at levels comparable to that of the Sham controls. Deoxypyridinoline excretion did not change except in the OVX-E2 group that showed an expected reduction when compared to the Sham and OVX controls. There were no treatment-related differences in total alkaline phosphatase or urinary NO metabolites. Tibial failure torque was comparable between the groups but both OVX+E2 and OVX+NG groups showed decreased torsional rigidity compared with the OVX controls. Endothelial and inducible NOS were found in osteoblast-like cells associated with calcifying cartilage spicules in the distal femoral metaphysis. These data confirm previous findings and show that nitroglycerin counteracts the estrogen deficiency-induced osteopenia in the ovariectomised rat model. Organic nitrates may thus be beneficial in conditions where bone turnover is compromised such as in osteoporosis.

Coronary atherosclerosis and somatic mutations: an overview of the contributive factors for oxidative DNA damage

Coronary artery disease (CAD) is a multifactorial process that appears to be caused by the interaction of environmental risk factors with multiple predisposing genes. Genetic research on CAD has traditionally focused on investigation aimed at identifying disease-susceptibility genes. Recent evidence suggests that somatically acquired DNA mutations may also contribute significantly to the pathogenesis of the disease, underlining the similarity between atherosclerotic and carcinogenic processes. The generation of oxidative stress has been emphasized as an important cause of DNA damage in atherosclerosis. This review highlights some of the major atherogenic risk factors as likely mediators in the oxidative modification of DNA. It also examines the hypothesis that an increase in oxidative stress may derive from "oxidatively" damaged mitochondria. Accordingly, further research in this field should be given high priority, since increased somatic DNA damage could be an important pathogenic factor and an additional prognostic predictor, as well as a potential target for therapeutic strategies in coronary artery disease.

Withdrawal of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors elicits oxidative stress and induces endothelial dysfunction in mice

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) improve endothelial function. We determined whether withdrawal of statin therapy affects endothelium-dependent relaxation in mice and studied the underlying mechanism. Mice were treated with daily injections of cerivastatin (2 mg/kg per day SC), atorvastatin (1 and 10 mg/kg per day SC), or placebo. Vascular reactivity was studied in aortic rings from these mice after 10 days of treatment and after cessation of therapy for several days. Both statins improved endothelium-dependent relaxation to acetylcholine. Compared with control, withdrawal of statin treatment transiently (from day 4 to 7) attenuated endothelium-dependent relaxation. In vessels from animals subjected to atorvastatin withdrawal, the antioxidant tiron restored relaxations. Vascular superoxide anion generation was unaffected by statin therapy but was increased during withdrawal. In mice lacking the gp91phox subunit of the NADPH oxidase, no attenuation of acetylcholine-induced relaxation and no increase in superoxide generation were observed after withdrawal of atorvastatin. In human umbilical vein endothelial cells, statins, which decrease the membrane association of NADPH oxidase-activating Rac-1, increased the activity of this GTPase in whole-cell lysates. Withdrawal of statins induced a translocation of Rac-1 from the cytosol to the membrane and transiently increased NADPH-induced lucigenin chemiluminescence in membrane preparations. Rac-1 inactivation by Clostridium difficile toxin B inhibited the cerivastatin-induced oxygen radical production in human umbilical vein endothelial cells. These observations indicate that the withdrawal of statins induces endothelial dysfunction. The underlying mechanism involves activation of a gp91phox-containing NADPH oxidase by Rac-1 and the subsequent scavenging of endothelium-derived NO by superoxide anions generated from this enzyme.

Prolonged exposure to YC-1 induces apoptosis in adrenomedullary endothelial and chromaffin cells through a cGMP-independent mechanism

YC-1, a benzyl indazole derivative, is an NO-independent direct activator of soluble guanylyl cyclase (sGC), which presents a synergistic action with NO in stimulating cGMP synthesis. These properties have served to suggest YC-1 as an attractive therapeutic agent by permitting the reduction of nitrovasodilator dosage and regulating endogenous cGMP metabolism. Here we studied the effect of prolonged exposure of adrenomedullary endothelial and chromaffin cells to YC-1. We found that YC-1 increased cGMP in the two types of cells and this action was blocked by the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). Cells underwent apoptotic death in association with increased caspase-3-like activity, DNA fragmentation, cytoskeletal disorganization and changes in membrane permeability after prolonged incubation with YC-1. Caspase-3-like protease activity and DNA fragments in the cytoplasm were increased in a dose-dependent manner by 16 h YC-1 treatment. The specific and cell permeable caspase-3-like protease inhibitor DEVD-CHO effectively inhibited YC-1-mediated caspase-3-like activation and DNA fragmentation. Moreover, YC-1 also induced cell shape changes accompanied by actin filament disorganization and alterations in membrane permeability. Cells incubated for 24h with YC-1 showed damaged membranes by binding to nucleic acid of a dye excluded by the intact plasma membrane of live cells. YC-1 also induced a decrease in the intracellular non-specific esterase activity, another indication of cell toxicity. Apoptotic phenomena were not prevented by the presence of ODQ although it effectively inhibited the YC-1-elicited cGMP increases. These findings indicate that YC-1 induces apoptosis by activating caspase-3-like protease through a mechanism independent of sGC activation.

Managed substitution of modified release nitrates with an asymmetric dosing regimen

BACKGROUND

Orally administered modified release organic nitrates are used commonly in the prophylaxis of myocardial ischaemia, although little evidence indicates a clinically superior response compared with standard formulated preparations administered symmetrically.

AIM

To investigate the clinical success of transfer of suitable patients from MR to SF nitrates.

METHOD

Suitable candidates for therapeutic substitution, assessed by a pharmacist, completed a baseline study to estimate frequency and timing of chest pain, the number of rescue doses of sublingual nitrates required, together with an assessment of adverse effects experienced. Following substitution to an eccentric dosing schedule, a further one month's assessment of chest pain frequency, rescue nitrate use and adverse effects was recorded and compared with baseline.

RESULTS

Twelve (37.5%) patients from a possible 32 candidates were invited to complete a baseline symptoms and adverse event diary. Eight patients entered the study phase (66.7% of the 12 included in the baseline phase of the study). These candidates showed no evidence of loss of control of chest pain symptoms, 3.5 +/- 1.16 (mean +/- standard error of mean) episodes/patient/28 days compared with 1.9 +/- 0.96 episodes/patient/28 days during the test phase (P > 0.05). Similarly, there was no difference in the number of doses of rescue nitrates required when the trial phase (2.6 +/- 1.63 doses/patient/28 days) was compared with the control (2.0 +/- 1.31 doses/patient/28 days, P > 0.05). There was no evidence of an increased incidence of adverse effects during the trial period of the study.

CONCLUSION

This small study suggests that, if selected carefully, therapeutic substitution of MR oral nitrates can be managed successfully without apparent risk of loss of symptom control or increased incidence of adverse effects.

Treatment of stable angina

Severe atherosclerotic narrowing of one or more coronary arteries is responsible for myocardial ischemia and angina pectoris in most patients with stable angina pectoris. The coronary arteries of patients with stable angina also contain many nonobstructive plaques, which are prone to fissures or rupture resulting in presentation of acute coronary syndromes (unstable angina, myocardial infarction, sudden ischemic death). In addition to symptomatic relief of symptoms and an increase in angina-free walking time with antianginal drugs or revascularization procedures, the recent emphasis of treatment has been to reduce adverse clinical outcomes (coronary death and myocardial infarction). The role of smoking cessation, aspirin, treatment of elevated lipids, and treatment of high blood pressure in all patients and of beta-blockers and angiotensin-converting enzyme inhibitors in patients with diminished systolic left ventricular systolic function in reducing adverse outcomes has been well established. What is unknown, however, is whether any anti-anginal drugs (beta-blockers, long-acting nitrates, calcium channel blockers) effect adverse outcomes in patients with stable angina pectoris. Recent trials evaluated the usefulness of suppression of ambulatory ischemia in patients with stable angina pectoris, but it remains to be established whether suppression of ambulatory myocardial ischemia with antianginal agents or revascularization therapy is superior to pharmacologic therapy targeting symptom relief. Patients who have refractory angina despite optimal medical treatment and are not candidates for revascularization procedures may be candidates for newer techniques of transmyocardial revascularization, enhanced external counterpulsation, spinal cord stimulation, or sympathectomy. The usefulness of these techniques, however, needs to be confirmed in large randomized clinical trials.

Isosorbide 5-mononitrate: a review of a sustained-release formulation (Imdur) in stable angina pectoris

Imdur (IMD) is a sustained-release isosorbide 5-mononitrate preparation for the treatment of chronic stable angina pectoris. Controlled medication release is achieved using the Durules principle of insoluble matrix embedding. Data from randomised double-blind trials show that IMD 60 mg once daily (the most widely studied dosage) has significant antianginal and anti-ischaemic effects compared with placebo after 2 weeks' treatment. Efficacy was generally observed approximately 1 to 12 hours after administration, indicating that once-daily administration in the morning will provide effective prophylaxis of symptoms throughout the day. Improvements from baseline are generally maintained during IMD repeated treatment. There was no evidence of classical tolerance to IMD 30 to 240 mg/day in a large well designed study. Although improvements from baseline were maintained over 6 weeks with IMD 30 or 60 mg/day, statistical significance versus placebo was eventually lost because of improved performance in the placebo group. IMD 120 or 240 mg/day were more effective than placebo after 6 weeks. Studies lasting up to 2 weeks found no evidence of tolerance to IMD 60 mg/day. In comparative trials lasting approximately 2 weeks, IMD 60 mg once daily was more effective than isosorbide dinitrate 30 mg 4 times daily and similar to or better than isosorbide dinitrate 20 mg 3 times daily. Preliminary data show that IMD 60 mg once daily has similar efficacy to diltiazem 60 mg 3 times daily and is at least as effective as certain other sustained-release isosorbide 5-mononitrate preparations. There is no evidence for rebound worsening of ischaemia 24 hours after IMD administration. Abrupt discontinuation during long term IMD treatment may exacerbate anginal symptoms. In general, IMD is well tolerated. The most frequently reported adverse event, headache, is usually mild to moderate, improves with long term therapy and rarely leads to treatment withdrawal. Patient compliance is better with once-daily administration of IMD than with twice-daily administration of conventional isosorbide 5-mononitrate.

CONCLUSIONS

In patients with chronic stable angina, IMD provides effective antianginal prophylaxis for up to 12 hours and does not seem to be associated with rebound phenomena at the end of the dosage interval. Improvements from baseline are maintained during repeated administration, although loss of statistically significant superiority over placebo was evident during 6 weeks' treatment with IMD < or =60 mg/day in 1 study. Further evaluation of comparative efficacy (particularly with respect to other sustained-release preparations) and long term effects would be beneficial. Nevertheless, the available data suggest that IMD is a useful and convenient agent for the treatment of patients with chronic stable angina pectoris.