Blood levels after sublingual nitroglycerin

An acute bout of prolonged sitting blunts popliteal endothelium-independent dilation in young, healthy adults

A single bout of prolonged uninterrupted sitting increases oxidative stress, reduces popliteal blood flow-induced shear stress, and diminishes endothelium-dependent, flow-mediated dilation (FMD). The FMD response is also influenced by the sensitivity of vascular smooth muscle cells to nitric oxide (i.e., endothelium-independent dilation), which is also attenuated by elevated oxidative stress. However, it is currently unknown whether prolonged sitting impacts popliteal endothelium-independent dilation responses, which may uncover a novel mechanism associated with sitting-induced vascular dysfunction. This study tested the hypothesis that prolonged sitting attenuates both popliteal FMD and endothelium-independent, nitroglycerin-mediated dilation responses (NMD, 0.4 mg sublingual dose). Popliteal blood flow (mL/min), relative FMD (%), and NMD (%) were assessed via duplex ultrasonography before and after a ∼3-h bout of sitting in 14 young, healthy adults (8♀; 22 ± 2 yr). Prolonged sitting attenuated resting blood flow (57 ± 23 to 32 ± 16 mL/min, P < 0.001), relative FMD (4.6 ± 2.8% to 2.2 ± 2.5%; P = 0.001), and NMD (7.3 ± 4.0% to 4.6 ± 3.0%; P = 0.002). These novel findings demonstrate that both endothelium-dependent and independent mechanisms contribute to the adverse vascular consequences associated with prolonged bouts of sitting.NEW & NOTEWORTHY We demonstrate that lower-limb vascular smooth muscle function is attenuated in young, healthy adults after an acute bout of prolonged sitting. These data indicate that prolonged sitting-induced vascular dysfunction involves both endothelium-dependent and -independent mechanisms.

Technical Considerations for Dynamic Myocardial Computed Tomography Perfusion as Part of a Comprehensive Evaluation of Coronary Artery Disease Using Computed Tomography

Dynamic myocardial computed tomography perfusion (DM-CTP) has good diagnostic accuracy for identifying myocardial ischemia as compared with both invasive and noninvasive reference standards. However, DM-CTP has not yet been implemented in the routine clinical examination of patients with suspected or known coronary artery disease. An important hurdle in the clinical dissemination of the method is the development of the DM-CTP acquisition protocol and image analysis. Therefore, the aim of this article is to provide a review of critical parameters in the design and execution of DM-CTP to optimize each step of the examination and avoid common mistakes. We aim to support potential users in the successful implementation and performance of DM-CTP in daily practice. When performed appropriately, DM-CTP may support clinical decision making. In addition, when combined with coronary computed tomography angiography, it has the potential to shorten the time to diagnosis by providing immediate visualization of both coronary atherosclerosis and its functional relevance using one single modality.

Vasodilatation by carbon dioxide and sodium nitroglycerin reduces compliance of the cerebral arteries in humans

NEW FINDINGS

What is the central question of this study? Vascular compliance importantly contributes to the regulation of cerebral perfusion and complex mechanisms are known to influence compliance of a vascular bed: while vasodilatation mediates changes in vascular resistance, does it also affect compliance, particularly in the cerebral vasculature? What is the main finding and its importance? Cerebral vasodilatation, elicited by hypercapnia and sodium nitroglycerin administration, reduced cerebrovascular compliance by approximately 26% from baseline. This study provides new insight into mechanisms mediating cerebrovascular compliance.

ABSTRACT

Changes in vascular resistance and vascular compliance contribute to the regulation of cerebral perfusion. While changes in vascular resistance are known to be mediated by vasodilatation, the mechanisms contributing to changes in vascular compliance are complex. In particular, whether vasodilatation affects compliance of the vasculature within the cranium remains unknown. Therefore, the present study examined the impact of two vasodilatation pathways on cerebrovascular compliance in humans. Fifteen young, healthy adults (26 ± 5 years, seven females) completed two protocols: (i) sublingual sodium nitroglycerin (SNG; 0.4 mg) and (ii) hypercapnia (5-6% carbon dioxide gas mixture for 4 min). Blood pressure waveforms (finger photoplethysmography) and middle cerebral artery blood velocity waveforms (transcranial Doppler ultrasound) were input into a modified Windkessel model and an index of cerebrovascular compliance (Ci) was calculated. During the SNG protocol, Ci decreased 24 ± 17% from baseline ((5.0 ± 2.3) × 10^-4  cm s^-1  mmHg^-1 ) to minute 10 ((3.6 ± 1.2) × 10^-4  cm s^-1  mmHg^-1 ; P = 0.009). During the hypercapnia protocol, Ci decreased 28 ± 9% from baseline ((4.4 ± 1.9) × 10^-4  cm s^-1  mmHg^-1 ) to minute 4 ((3.1 ± 1.4) × 10^-4  cm s^-1  mmHg^-1 ; P < 0.001). Cerebral vasodilatory stimuli induced by nitric oxide and carbon dioxide mechanisms reduced compliance of the cerebral vascular bed by approximately 26% from supine baseline values.

Submental nalbuphine exhibits improved efficacy in ameliorating acute pain in prehospital emergent conditions; a comparative study with conventional intramuscular using gamma scintigraphy

BACKGROUND

Nalbuphine (NLB) is a kappa-agonist and mu-partial antagonist, widely used for opioid withdrawal de-addiction, opioid-induced pruritis and as emergent analgesia.

OBJECTIVE

The present study aimed to assess the safety and efficacy of NLB in pain sensitization, through a submental route so as to provide faster management in emergent situations.

MATERIALS & METHODS

In-vivo efficacy and safety studies of NLB-submental injection were assessed in Sprague-Dawley(SD) rats. For eddy's hot plate study, animals were allocated into three groups, the first group served as normal control; group II received NLB (through submental route at 1.2 mg/kg); group III received NLB (through intramuscular route at 1.2 mg/kg). Response latency (in terms of response latency) was measured at 10, 30 & 60 min in all the experimental groups. Safety studies were carried out according to OECD 423. In-vitro release study was conducted using a cellulose dialysis membrane (12,000 KDa). The biodistribution and release kinetics studies were carried out using gamma scintigraphy studies in New Zealand rabbits and humans respectively.

RESULTS

The response latency of NLB from the submental route was found to be 7.17 (SD 1.47) seconds and in the case of the intramuscular route it was calculated as 4.00 (SD 1.26) seconds at 10 min. The data depicts the better efficacy of submental injection in ameliorating pain than the intramuscular injection. Toxicity studies predict the safe profile through a submental route. The release kinetics in humans of submental NLB was 46% faster as compared to the intramuscular site of injection. The NLB injection through both routes was compared by non-invasive gamma scintigraphy technique and we found that submental injection has faster (within 10 min) onset of action & distributes rapidly.

CONCLUSION

The submental route of NLB is faster, more efficacious than the intramuscular route. Thus, we conclude that in the case of emergent scenarios (i.v or i.m. route is compromised), where immediate relief is necessary, the submental route is a preferred choice.

Sodium nitroglycerin induces middle cerebral artery vasodilatation in young, healthy adults

NEW FINDINGS

What is the central question of this study? Nitric oxide causes dilatation in peripheral vessels; however, whether nitric oxide affects basal cerebral artery dilatation has not been explored. What is the main finding and its importance? This study demonstrated that vasodilatation occurs in the right middle cerebral artery in response to exogenous nitric oxide. However, blood velocity decreased and, therefore, overall cerebral blood flow remained unchanged. This study provides new insight into the role of nitric oxide in cerebral blood flow control.

ABSTRACT

Recent evidence indicates that basal cerebral conduit vessels dilate with hypercapnia, with a nitric oxide (NO) mechanism explaining one way in which parenchymal cerebral arterioles dilate. However, whether NO affects basal cerebral artery dilatation remains unknown. This study quantified the effect of an exogenous NO donor [sodium nitroglycerin (NTG); 0.4 mg sublingual spray] on the right middle cerebral artery (rMCA) cross-sectional area (CSA), blood velocity and overall blood flow. Measures of vessel CSA (7 T magnetic resonance imaging) and MCA blood velocity (transcranial Doppler ultrasound) were made at baseline (BL) and after exogenous NTG or placebo (PLO) administration in young, healthy individuals (n = 10, two males, age range 20-23 years). The CSA increased in the rMCA [BL, 5.2 ± 1.2 mm² ; PLO, 5.4 ± 1.5 mm² ; NTG, 6.6 ± 1.5 mm² , P < 0.05; mean ± SD]. Concurrently, rMCA blood velocity decreased from BL during NTG compared with PLO (BL, 67 ± 10 cm s^-1 ; PLO, 62 ± 10 cm s^-1 ; NTG, 59 ± 9.3 cm s^-1 , P < 0.05; mean ± SD]. However, total MCA blood flow did not change with NTG or PLO [BL, 221 ± 37.4 ml min^-1 ; PLO, 218 ± 35.0 ml min^-1 ; NTG, 213 ± 46.4 ml min^-1 ). Therefore, exogenous NO mediates a dilatory response in the rMCA, but not in its downstream vascular bed.

Pain Relieving Effect of Sublingual Glycerol Trinitrate in Renal Colic: a Randomized Placebo-Controlled Trial

Introduction:

Renal colic is caused by colicky spasms of ureters. As has been shown in previous experiments, glycerol trinitrate (TNG) can inhibit these muscular spasms.

Objective:

This study was performed to assess the pain relieving effect of TNG among patients referred due to renal colic pain to the emergency department (ED).

Methods:

This study is a randomized, placebo-controlled study on 60 patients with renal colic who were referred to the ED, who were diagnosed clinically to have renal colic, and their pain was more than 5 based on a visual analogue scale (VAS). The patient's pain was recorded at the moment of clinical diagnosis, and each one received one capsule, either 0.4 mg TNG or placebo, plus a 100 mg indomethacin suppository. The pain score was re-assessed after 5 and 30 min. The values were recorded and compared using SPSS-16 software.

Results:

Sixty patients with a mean age of 35.75 ± 11.99 years were enrolled (73.3% male). Patients in the two groups were matched for age (p = 0.290), sex (p = 0.559), and the presence of microscopic hematuria (p = 0.292). Pain relief from the start point until the end of the intervention was statistical different in all studied patients (p < 0.05); but the comparison between the two groups showed no significant difference in this regard (p = 0.440).

Conclusion:

It is likely that adding TNG to an indomethacin suppository had no significant effects on better pain management of patients referred with renal colic to the ED.

Role of short-acting nitroglycerin in the management of ischemic heart disease

Nitroglycerin is the oldest and most commonly prescribed short-acting anti-anginal agent; however, despite its long history of therapeutic usage, patient and health care provider education regarding the clinical benefits of the short-acting formulations in patients with angina remains under-appreciated. Nitrates predominantly induce vasodilation in large capacitance blood vessels, increase epicardial coronary arterial diameter and coronary collateral blood flow, and impair platelet aggregation. The potential for the prophylactic effect of short-acting nitrates remains an under-appreciated part of optimal medical therapy to reduce angina and decrease myocardial ischemia, thereby enhancing the quality of life. Short-acting nitroglycerin, administered either as a sublingual tablet or spray, can complement anti-anginal therapy as part of optimal medical therapy in patients with refractory and recurrent angina either with or without myocardial revascularization, and is most commonly used to provide rapid therapeutic relief of acute recurrent angina attacks. When administered prophylactically, both formulations increase angina-free walking time on treadmill testing, abolish or delay ST segment depression, and increase exercise tolerance. The sublingual spray formulation provides several clinical advantages compared to tablet formulations, including a lower incidence of headache and superiority to the sublingual tablet in terms of therapeutic action and time to onset, while the magnitude and duration of vasodilatory action appears to be comparable. Furthermore, the sublingual spray formulation may be advantageous to tablet preparations in patients with dry mouth. This review discusses the efficacy and utility of short-acting nitroglycerin (sublingual spray and tablet) therapy for both preventing and aborting an acute angina attack, thereby leading to an improved quality of life.

Sublingual Nitroglycerin Administration in Coronary Computed Tomography Angiography: a Systematic Review

OBJECTIVE

To systematically investigate the literature for the influence of sublingual nitroglycerin administration on coronary diameter, the number of evaluable segments, image quality, heart rate and blood pressure, and diagnostic accuracy of coronary computed tomography (CT) angiography.

METHODS

A systematic search was performed in PubMed, EMBASE and Web of Science. The studies were evaluated for the effect of sublingual nitroglycerin on coronary artery diameter, evaluable segments, objective and subjective image quality, systemic physiological effects and diagnostic accuracy. Due to the heterogeneous reporting of outcome measures, a narrative synthesis was applied.

RESULTS

Of the 217 studies identified, nine met the inclusion criteria: seven reported on the effect of nitroglycerin on coronary artery diameter, six on evaluable segments, four on image quality, five on systemic physiological effects and two on diagnostic accuracy. Sublingual nitroglycerin administration resulted in an improved evaluation of more coronary segments, in particular, in smaller coronary branches, better image quality and improved diagnostic accuracy. Side effects were mild and were alleviated without medical intervention.

CONCLUSION

Sublingual nitroglycerin improves the coronary diameter, the number of assessable segments, image quality and diagnostic accuracy of coronary CT angiography without major side effects or systemic physiological changes.

KEY POINTS

• Sublingual nitroglycerin administration results in significant coronary artery dilatation. • Nitroglycerin increases the number of evaluable coronary branches. • Image quality is improved the most in smaller coronary branches. • Nitroglycerin increases the diagnostic accuracy of coronary CT angiography. • Most side effects are mild and do not require medical intervention.

Combined coronary lumen and vessel wall magnetic resonance imaging with i-T2prep: influence of nitroglycerin

It has been shown that sublingual nitroglycerin (NTG) improves image quality of coronary lumen magnetic resonance angiography. Our aim was to investigate the influence of NTG on coronary lumen and vessel wall image quality using a combined, single sequence approach (i-T2prep), which is able to image both within the known time frame of action of NTG. Ten healthy volunteers underwent right coronary artery lumen and vessel wall imaging using the i-T2prep sequence before and after administration of NTG. Image quality was assessed qualitatively and quantitatively. Diameter, length and wall thickness were also measured using dedicated semi-automatic software. NTG induced coronary vasodilatation (lumen diameter increased from 2.16 ± 0.32 to 2.52 ± 0.59 mm; p = 0.036). As a result, visualized lumen length (9.8 ± 2.6 to 11.4 ± 3.3 cm; p = 0.025) and qualitative lumen image quality (median 3 (interquartile range 2-3.25) vs. median 3 (interquartile range 3-4); p = 0.046) both improved. Vessel wall imaging also demonstrated a significant improvement in vessel wall sharpness after NTG (24.8 vs. 27.3 %; p = 0.036). This study demonstrates the benefits of NTG for coronary lumen and vessel wall imaging using a combined sequence, i-T2prep. The methodology described here has great potential for future pathophysiological studies.

Efficacy of different forms of nitrates in angina pectoris

Nitroglycerin has maintained its position in the treatment of angina pectoris for more than a century. Efficacy of oral nitrates has been established and compares well with that of other anti-anginal drugs. New delivery systems are being developed for sustained systemic nitrate action. Beneficial action of nitrates in congestive heart failure and their crucial role in unstable angina and acute myocardial infarction has further widened their therapeutic use. A plausible hypothesis of the mechanism of nitrate-induced vasodilation has been presented, involving production of nitrosothiols and activation of guanylate cyclase in the vascular smooth muscle. Recent developments suggest that the rate degradation of nitrates and formation of nitrosothiols in the vascular smooth muscle are linked, offering an explanation to the relatively rapidly developing, but partial vascular tolerance during high-dose nitrate therapy.

Nitroglycerin attenuates human endothelial progenitor cell differentiation, function, and survival

Endothelial progenitor cells (EPCs) participate in angiogenesis and the response to chronic ischemia. Risk factors and cardiovascular disease attenuate EPC number, function, and survival. Continuous therapy with nitroglycerin (glyceryl trinitrate; GTN) is associated with increased vascular oxidative stress, leading to nitrate tolerance and endothelial dysfunction. Thus, GTN therapy may also affect EPCs. The purpose of this study was to determine whether continuous exposure to GTN in vivo or during ex vivo expansion affects the circulating number and functional characteristics of human EPCs. To determine the effects of continuous in vivo GTN exposure, EPCs isolated from 28 healthy males before and after receiving 0.6 mg/h GTN (n=17) or no treatment (n=11) for 1 week were expanded for 6 days and compared. To determine the effects of continuous ex vivo GTN exposure, EPCs isolated before randomization were expanded for 6 days in medium supplemented with 100 nM, 300 nM, or 1 microM GTN. EPCs expanded without GTN served as controls (n=10). In vivo, GTN exposure significantly increased the percentage of circulating cells expressing the EPC marker CD34 and increased the susceptibility of expanded EPCs to apoptosis but had no impact on the phenotypic differentiation or migration of EPCs. Ex vivo, GTN exposure increased apoptosis while decreasing phenotypic differentiation, migration, and mitochondrial dehydrogenase activity of EPCs, compared with EPCs expanded in the absence of GTN. Taken together, these results suggest that continuous GTN therapy might impair EPC-mediated processes, an effect that could be detrimental in the setting of ischemic cardiovascular disease.

Clinical pharmacokinetics and pharmacodynamics of glyceryl trinitrate and its metabolites

This review discusses the pharmacokinetics and pharmacodynamics of glyceryl trinitrate (nitroglycerin; GTN) pertinent to clinical medicine. The pharmacokinetics of GTN associated with various dose regimens are characterised by prominent intra- and inter-individual variability. It is, nevertheless, important to clearly understand the pharmacokinetics and characteristics of GTN to optimise its use in clinical practice and, in particular, to obviate the development of tolerance. Measurements of plasma concentrations of GTN and of 1,2-glyceryl dinitrate (1,2-GDN), 1,3-glyceryl dinitrate (1,3-GDN), 1-glyceryl mononitrate (1-GMN), and 2-glyceryl mononitrate (2-GMN), its four main metabolites, remain difficult and require meticulous techniques to obtain reliable results. Since GDNs have an effect on haemodynamic function, pharmacokinetic analyses that include the parent drug as well as the metabolites are important. Although the precise mechanisms of GTN metabolism have not been elucidated, two main pathways have been proposed for its biotransformation. The first is a mechanism-based biotransformation pathway that produces nitric oxide (NO) and contributes directly to vasodilation. The second is a clearance-based biotransformation or detoxification pathway that produces inorganic nitrite anions (NO(2) -). NO(2) - has no apparent cardiovascular effect and is not converted to NO in pharmacologically relevant concentrations in vivo. In addition, several non-enzymatic and enzymatic systems are capable of metabolising GTN. This complex metabolism complicates considerably the evaluation of the pharmacokinetics and pharmacodynamics of GTN. Regardless of the route of administration, concentrations of the metabolites exceed those of the parent compound by several orders of magnitude. During continuous steady-state delivery of GTN, for instance by a patch, concentrations of 1,2-GDN are consistently 2-7 times higher than those of 1,3-GDN, and concentrations of 2-GMN are 4-8 times higher than those of 1-GMN. Concentrations of GDNs are approximately 10 times higher, and of GMNs approximately 100 times higher, than those of GTN during sustained administration. The development of tolerance is closely related to the metabolism of GTN, and can be broadly categorised as haemodynamic tolerance versus vascular tolerance. Efforts are warranted to circumvent the development of tolerance and facilitate the use of GTN in clinical practice. Although this remains to be accomplished, it is likely that, in the near future, regimens will be developed based on a full understanding of the pharmacokinetics and pharmacodynamics of GTN and its metabolites.

Treatment of Perioperative Myocardial Ischemia

Prevention and treatment of myocardial ischemia re mains a central focus of perioperative care. Myocardial ischemia is best understood in terms of myocardial oxygen supply and demand ratios. Conventional ther apy includes nitrates, β-blockers, and calcium channel blockers. In all 3 drug classes, ischemia is reduced by either improving supply, decreasing demand, or both. More recent investigation evaluates these medications either as prophylactic therapy or as a component of long-term risk reduction for cardiac morbid events. Newer therapies, including anticoagulation, pain ther apy, normothermia, central neuroaxial techniques, and other therapies, are reviewed.

Comparison of nitroglycerin lingual spray and sublingual tablet on time of onset and duration of brachial artery vasodilation in normal subjects

This study compared the rapidity of onset, the magnitude, and the duration of action of 2 short-acting nitroglycerin preparations using high-resolution brachial ultrasound. Both sublingual tablet and lingual spray formulations caused maximal vasodilation at 3 minutes; however, the spray provided faster (at 2 minutes), greater, and more prolonged (15 minutes) vasodilation than the tablet.

The nitura study--effect of nitroglycerin or urapidil on hemodynamic, metabolic and respiratory parameters in hypertensive patients with pulmonary edema

OBJECTIVE

To assess the effects of nitroglycerin or urapidil on hemodynamic, respiratory and metabolic parameters in hypertensive patients with pulmonary edema.

DESIGN

Open, randomized and prospective clinical study.

SETTING

Out-of-hospital setting and Emergency Department in a 2000-bed hospital.

PATIENTS

Hundred twelve patients with evidence of hypertensive crises with pulmonary edema (systolic blood pressure (SBP) > 200 mmHg and/or diastolic blood pressure (DBP) > 100 mm Hg and rales over both lungs) at the time when the emergency physician arrived.

INTERVENTIONS

The out-of-hospital treatment consisted of oxygen via face mask, 80 mg furosemide i.v., 10 mg morphium s.c., and either nitroglycerin sublingually (initial dose: 0.8 mg; repetitive administration of 0.8 mg every 10 min to a cumulative dose of 3.2 mg) or urapidil (initial dose: 12.5 mg i.v.; repetitive administration every 15 min to a cumulative dose of 50 mg). If SBP was more than 180 mm Hg and/or DBP more than 90 mm Hg on admission, antihypertensive treatment was continued with nitroglycerin (0.3-3 mg/h) or urapidil (5-50 mg/h).

MEASUREMENTS AND RESULTS

Blood pressure (BP) was measured every 5 min with the use of an automatic oscillometric device. Serum lactate, PO2, pH value, and base excess (BE) were evaluated on admission and 6 h later. Blood pressure, serum lactate and BE on admission were significantly lower (SBP: 155 +/- 30 vs 179 +/- 33 mm Hg; p = 0.0002; DBP: 82 +/- 17 vs 93 +/- 19 mmHg; p = 0.001; lactate: 2.2 +/- 1.6 vs 3.9 +/- 2.7; p = 0.0001; BE: -1.9 +/- 3.9 vs -4.4 +/- 1.7; p = 0.0005) and PO2 and pH values were significantly higher in the urapidil group compared to the nitroglycerin group (PO2: 75 +/- 25 vs 66 +/- 17; p = 0.036; pH: 7.33 +/- 0.08 vs 7.29 +/- 0.09; p = 0.042). After 6 h no differences between the two groups were observed.

CONCLUSION

The more pronounced BP reduction in the urapidil group was associated with an improved respiratory and metabolic situation in hypertensive patients with pulmonary edema. Therefore, urapidil is a valuable alternative to nitroglycerin in patients with pulmonary edema and systemic hypertension.

Assessment of the drug interaction between intravenous nitroglycerin and heparin

OBJECTIVE

To assess whether a clinically significant interaction occurs between heparin and nitroglycerin (NTG).

METHODOLOGY

Activated partial thromboplastin time (APTT) was measured in patients with unstable angina who were stabilized on intravenous NTG and heparin just prior to weaning the NTG infusion, and one and four hours after stopping the NTG.

RESULTS

In 22 heparin-treated patients (20 men, 2 women; aged 56.7 +/- 10 years; weight 79.5 +/- 15 kg), the APTT ratio was inversely related to the dose of NTG (slope = -0.003; p < 0.05). However, there were no significant differences between the APTT values measured before and after discontinuation of NTG (p = 0.8511).

CONCLUSIONS

Our study demonstrates a clinically insignificant interaction between NTG and heparin at NTG doses commonly used in patients.

Issues in contemporary drug delivery. Part VI: Advanced cardiac drug formulations

OBJECTIVE

To identify and discuss the clinical utility of new delivery systems and formulations of cardiac drugs.

DATA SOURCES

Studies describing or evaluating new drug delivery systems for cardiac drugs were identified through a MEDLINE literature search.

STUDY SELECTION

All studies describing or evaluating new delivery systems for cardiac drugs were reviewed.

DATA EXTRACTION

Data were abstracted and evaluated by each author independently.

DATA SYNTHESIS

The most common oral sustained-release formulations include the wax-matrix system, the gastrointestinal therapeutic system (GITS), and the spheroidal oral drug absorption system (SODAS). The wax-matrix delivery system is limited by the occurrence of "dose-dumping." In a low-pH setting, the wax-matrix formulation may dissolve too rapidly, liberating the entire dose in a short period of time. The clinical relevance of this phenomenon is unknown. The GITS and SODAS formulations are less likely to be affected by pH and food. Nitroglycerin is available by many routes of administration. The topical patch forms are convenient to use, but are associated with the development of tolerance. A buccal formulation incorporates a relatively short onset of effect with a three- or four-times-daily dosing regimen. Although tolerance is less of a problem with buccal nitroglycerin than with topical nitrates, this formulation is less convenient to use because of buccal irritation and interference with eating and talking. A new spray formulation of nitroglycerin offers longer shelf-life storage stability and an easier mode of administration. The spray canister is stable for three years compared with 12 weeks for an opened bottle of sublingual nitroglycerin tablets. Sublingual administration of oral cardiac drugs offers the potential for a more rapid onset of effects. Although nifedipine is often given sublingually, objective data indicate that it is not absorbed buccally but rather in the stomach. It appears that the chew-and-swallow route is most appropriate for nifedipine. Captopril is absorbed sublingually but its efficacy has not been demonstrated. Transdermal clonidine improves compliance and is associated with fewer adverse effects than oral clonidine. Transdermal formulations of beta-blockers are currently being evaluated.

CONCLUSIONS

Further advancements in the development of novel delivery systems for cardiac drugs are expected in the future.

Use of nitrates in ischemic heart disease

The organic nitrates have remarkably diverse actions that are or should be beneficial in patients with ischemic heart disease. These drugs are effective in all the important ischemic syndromes. Preliminary data in patients with acute infarction suggest that the drugs may be truly cardioprotective, resulting in improved mortality. This review has not discussed the role of nitrates in congestive heart failure or LV dysfunction, a subject of great importance. The nitrates are useful adjunctive agents in these syndromes, and the two VeHfT trials support the concept that long-term nitrate administration, in conjunction with hydralazine, may favorably alter the natural history of heart failure. This cardioprotective effect is similar to that suggested for the post-MI patient. The data are not strong enough for definitive conclusions at this time. The clinical benefits of nitrates in decreasing subjective (angina) and objective indices of ischemia in stable and unstable angina, as well as limited data in asymptomatic myocardial ischemia, are unequivocal and are as favorable as those for beta blockers or calcium antagonists. Tolerance is an important problem that unfavorably influences the potential benefits of nitrate therapy. I believe that this problem can be avoided with well-designed dosing regimens. Current research into endothelial biology in health and disease has further supported a physiologic role for the organic nitrates in patients with ischemic heart disease. The nitrate-platelet story, while controversial, is promising and offers another positive rationale for nitrate administration. The concept of nitrates replenishing disordered EDRF release or action is an exciting one. Physicians should feel fortunate to have such a remarkable group of drugs available for their patients.

Plasma disposition and hemodynamic effects of a single oral dose of isosorbide dinitrate in human males and females

The goal of the present work was to determine the plasma disposition and hemodynamic effects of isosorbide dinitrate (ISDN) in human males and females. Fourteen healthy human volunteers took part in the study; seven males, 21.7 +/- 2.5 y (SD), and seven females, 20.7 +/- 3.4 y. Measurements of forearm blood flow (FBF), vascular conductance (FVC), and venous capacitance (Cv) were obtained by venous occlusion plethysmography, whereas blood pressure was measured by automatic sphygmomanometry. Blood samples were taken through a catheter placed in the antecubital vein at 0, 15, 30, 45, 60, 90, 120, 360, 480, 720, and 1440 min following a single 10 mg oral dose of ISDN. Plasma concentrations of ISDN and its mononitrate metabolites, isosorbide-2-mononitrate (2-ISMN) and isosorbide-5-mononitrate (5-ISMN), were determined by large bore capillary column gas-liquid chromatography. Hemodynamic measurements were made at corresponding experimental times up to 480 min. No differences were observed in the disposition of ISDN, 2-ISMN or 5-ISMN between the male and female volunteers. In addition, the plasma concentrations of ISDN and its mononitrate metabolites did not consistently correlate with the hemodynamic changes of the individual subjects. Diastolic blood pressure was significantly decreased for a 0.5 h period starting at 30 min, which was the time at which plasma ISDN concentrations peaked, and which preceded the time when the plasma concentrations of 2-ISMN and 5-ISMN were maximal. These observations indicate that, for a single 10 mg oral dose of ISDN, there were no gender-dependent differences in the plasma disposition of the parent drug or its mononitrate metabolites, and the vascular changes responsible for the decrease in diastolic blood pressure in these volunteers occurred in vascular beds other than those of skeletal muscle as represented by forearm blood flow.

Assay of glyceryl trinitrate, isosorbide dinitrate, and their metabolites in plasma by large-bore capillary column gas-liquid chromatography

Two large-bore capillary columns, one with dimethyl polysiloxane (HP-1) as the stationary phase and the other with phenyl (50 per cent) methyl (50 per cent) polysiloxane (DB-17), were used to develop gas-liquid chromatographic (GLC) assays for measuring isosorbide dinitrate (ISDN), glyceryl trinitrate (GTN), and their metabolites. ISDN, isosorbide-2-mononitrate (2-ISMN), and isosorbide-5-mononitrate (5-ISMN) in plasma, ranging in concentration from 1 to 300 nM, and GTN, glyceryl-1,2-dinitrate (1,2-GDN), and glyceryl-1,3-dinitrate (1,3-GDN), ranging in concentration from 3 to 60 nM in plasma, were analysed on both columns. GLC analysis yielded baseline resolution of the analytes. The method using the dimethyl polysiloxane column gave a lower limit of detectability for GTN of 0.75 nM (signal/noise (s/n) = 2), and the procedure using the phenyl-methyl column provided a lower limit of detectability for ISDN of 81 pM (s/n = 2). The large-bore column GLC procedures exhibited shorter retention times for both ISDN and GTN than those previously reported for capillary-column assays. The chromatographic resolution of analytes and column efficiency of the large-bore capillary columns were comparable to the results previously found using capillary-column GC. The assays for ISDN and GTN have been shown to be appropriate for pharmacokinetic studies in volunteers and patients. We determined that the HP-1 column is appropriate for the analysis of GTN and metabolites, and the DB-17 column is suitable for analysis of ISDN and its metabolites. We conclude that the use of large-bore capillary columns provides rapid and reliable GLC assays for organic nitrates.

A dose-finding study of the hemodynamic effect of isosorbide dinitrate spray in congestive heart failure

A dose-finding study of the hemodynamic effect of a new formulation of isosorbide dinitrate (ISDN) spray was performed in 12 patients with chronic congestive heart failure. Doses of 1.25, 2.5, 5.0 mg and placebo, as 1 squirt, were randomly given to all patients. Hemodynamic measurements were performed by a Swan-Ganz catheter before and at 30 seconds and 1, 5, 10, 20 and 30 minutes after drug administration and every 30 minutes thereafter, until return of hemodynamic variables to baseline. Hemodynamic improvement evident as decreases in right-sided pressures and an increase in cardiac output was observed within 1 minute from administration of ISDN spray, and peaked at 5 minutes. Near maximal effect was achieved by the 2.5-mg dose. Thus, 2.5 mg of ISDN spray (new formulation) dose. Thus, 2.5 mg of ISDN spray (new formulation) produces rapid, near-maximal hemodynamic improvement in patients with congestive heart failure.

Stable angina pectoris: 3. Medical treatment

The therapeutic goals for the patient with angina pectoris are to minimize the frequency and severity of angina and to improve functional capacity at a reasonable cost and with as few side effects as possible. An integrated approach necessitates attention to conditions that might be aggravating angina, such as anemia or hypertension. Alterations in life-style and personal habits, such as cessation of cigarette smoking, are often necessary and should be continually reinforced by the physician. Certain concomitant diseases, such as chronic obstructive pulmonary disease, may influence the selection of drug therapy. Nitrates, beta-adrenergic blockers, and calcium entry blockers are the major classes of drugs that can be used alone or in combination in a program that is designed for the individual patient.

Sustained high-dose nitroglycerin transcutaneous patch therapy in angina pectoris: evidence for attenuation of effect over time

The safety and efficacy of using continuous high-dose transcutaneous nitroglycerin in doses up to 100 mg/24 hours in chronic stable angina was assessed in 20 patients using serial treadmill testing. Patients had first to show a response to sublingual nitroglycerin with a 20% improvement in exercise time. All patients were then titrated with 20 mg (40 cm2), 60 mg (120 cm2), 80 mg (160 cm2) or 100 mg (200 cm2) patches, until intolerable headache in association with a 10 mmHg reduction in blood pressure and a ten-beat increment in heart rate. Drug was then discontinued for 2 days and patients underwent three repeat stress tests to reestablish a consistent drug-free baseline. Patients were then randomized in double-blind fashion to receive either active patch (N = 11) in previous titration dose or placebo patch (N = 9), with treadmill tests performed at 0 (1 hour after previous patch removal), 4, and 24 hours after patch application at baseline and at weeks 1 and 2. Venous blood was obtained for measurement of plasma nitroglycerin levels. After the first 24 hours of active patch therapy, there was a significant reduction in systolic blood pressure (P = .05), a significant increase in heart rate (P = .01), and a minor increase in exercise tolerance (P = .06) compared to placebo. At weeks 1 and 2, there was an attenuation of drug effect in all of these parameters. Plasma nitroglycerin levels demonstrated consistently high plasma levels over each 24-hour dosing interval, on day 1, week 1, and week 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue distribution of glyceryl trinitrate and the effect on cGMP levels in rat

In order to study distribution in tissue, rats were treated subcutaneously with glyceryl trinitrate, GTN, (50 mg/kg). The concentrations of GTN were measured in plasma, brain, heart, adipose tissue and aortic tissue at different sampling times by a gas chromatographic method with electron-capture detection. The peak GTN-concentration was reached after 2 hours in all tissues examined. The highest concentration of GTN was found in adipose tissue, where the level was approximately forty times higher than in plasma. The concentration of GTN in brain, heart and aortic tissue was about 2-3 times as high as in plasma. The cGMP level was measured in heart and brain. An increase of the cGMP level was found in brain 2 hours after GTN administration. No cGMP increase was found in heart tissue. The results indicate a substantial distribution of GTN to tissue, and an increase of cGMP in brain. The distribution of the substance in the tissues as shown, might have both pharmacokinetic and pharmacodynamic implications.

Organic nitrate reductase: reassessment of its subcellular localization and tissue distribution and its relationship to the glutathione transferases

1. Using a specific and sensitive GLC method for the determination of glyceryl trinitrate (GTN), its subcellular and tissue distribution were reassessed. Liver was the most active tissue, but activity was also detected in the heart, kidney and gut. In all tissues activity was localized in the soluble fraction. The activity of soluble glutathione S-transferase followed the same pattern, liver exhibiting the highest and the heart the lowest activity. 2. Pretreatment with phenobarbitone and 3-methylcholanthrene stimulated both the glutathione S-transferase and organic nitrate reductase activities. 3. Glutathione S-transferase activity was competitively inhibited by GTN. 4. A comparison of the plasma and hepatic metabolism of GTN revealed higher drug affinity for the hepatic enzyme.

Relationship of pharmacokinetic and pharmacodynamic properties of the organic nitrates

Glyceryl trinitrate (nitroglycerin), isosorbide dinitrate and isosorbide mononitrate are, in various formulations, available for clinical use. The pharmacokinetics of glyceryl trinitrate are complex and only 1% of the drug administered orally can be detected in the plasma due to a pronounced arteriovenous concentration gradient, hydrolysis in the blood, and rapid denitration in the liver. There is a poor and usually transient correlation between plasma concentrations and therapeutic effects, due in part to the complex pharmacokinetics of glyceryl trinitrate, but primarily due to development of tolerance during continuous administration, either via the intravenous or cutaneous route. Isosorbide dinitrate kinetics are complicated by its extensive metabolism into 2- and 5-mononitrates, which are pharmacologically active, and which also accumulate more than the parent drug during long term treatment. These facts, combined with development of tolerance during long term therapy, preclude the establishment of a concentration-response relationship. Isosorbide-5-mononitrate has ideal and dose-linear kinetics and is nearly 100% bioavailable after oral administration. However, tolerance develops during long term therapy, and therefore a relationship between plasma concentrations and clinical effects cannot be established. On the basis of available data, plasma concentrations of various nitrates do not reliably predict clinical effects.

Recent developments in the use of nitrates for treatment of angina pectoris

Organic nitrates are effective in the treatment and prophylaxis of angina pectoris. The major clinical problem of tolerance may be avoided if the daily plasma concentrations of the active metabolite, isosorbide-5-mononitrate are maintained at 100-300 ng/ml. The most promising development in achieving this is the use of sustained release preparations.

The effect of aspirin on the hemodynamic response to nitroglycerin

The role of prostaglandins in mediating the hemodynamic response to nitroglycerin in vivo is controversial. To determine the effect of inhibiting prostaglandin production on the response to nitroglycerin, either placebo or aspirin (650 mg) was administered 1 hour prior to the administration of nitroglycerin (432 micrograms) sublingually to 40 healthy volunteers in a double-blind, randomized, cross-over study. Prior to nitroglycerin administration, blood pressure and pulse rate were determined noninvasively every 2 minutes until stable conditions were reached, and then after nitroglycerin administration determinations were made every 1 minute for the first 10 minutes, every 2 minutes for the next 10 minutes, and every 5 minutes until 30 minutes had elapsed. At peak response in the placebo study, nitroglycerin lowered systolic pressure from 117 +/- 10 to 111 +/- 10 mm Hg (p less than 0.0001). Unexpectedly, nitroglycerin increased diastolic pressure from 75 +/- 8 to 80 +/- 7 mm Hg (p less than 0.005), thus reducing pulse pressure significantly. Pulse rate after nitroglycerin increased from 72 +/- 11 to 85 +/- 14 (p less than 0.001). Aspirin slightly modified the pattern of response at 1 minute but altered neither the peak hemodynamic responses nor the areas under the time-pressure and time-pulse curves. Thus nitroglycerin-induced prostaglandin production does not play a major role in the systemic hemodynamic response to nitroglycerin in vivo.

Increased exercise tolerance and reduced duration of ischemia after isosorbide dinitrate oral spray in angina pectoris

The prophylactic and therapeutic anti-ischemic efficacy of isosorbide dinitrate (ISDN) oral spray was assessed in 10 patients with coronary artery disease and stable angina pectoris. The patients entered a randomized crossover study of ISDN spray and placebo, involving bicycle exercise testing. Each patient underwent 2 exercise tests at least 4 hours apart. Immediately before initiation of exercise they received either ISDN spray or placebo and crossed over during the other test. ISDN spray delayed the onset of anginal pain by about 40%, from a mean of 5.1 +/- 1.4 minutes with placebo to 7.2 +/- 1.3 minutes with the active drug (p less than 0.001). Time of onset of ST-segment depression was also significantly prolonged, from 7.1 +/- 1.5 minutes with placebo to 10.2 +/- 1.2 minutes with ISDN (p less than 0.001). The patients achieved a higher double product at onset of pain with ISDN than with placebo. The drug also reduced the time of disappearance of pain after discontinuation of exercise from 3.2 +/- 0.7 to 2.1 +/- 0.8 minutes (p less than 0.001), and the time of disappearance of electrocardiographic changes from 4.2 +/- 0.6 to 2.5 +/- 0.8 minutes (p less than 0.005). These findings indicate that oral ISDN spray is an effective prophylactic for exercise-induced angina. Its rapid onset of action makes it especially suitable for usage immediately before exercise.

More rapid relief of pain with isosorbide dinitrate oral spray than with sublingual tablets in elderly patients with angina pectoris

To evaluate the possibility of improving clinical practice in the treatment of angina pectoris, the duration of relief of pain with isosorbide dinitrate (ISDN) oral spray and sublingual tablets were compared in elderly patients with chronic stable angina pectoris. Nine patients (mean age 67 years) were studied in a randomized crossover trial. The patients underwent bicycle ergometry, which resulted in typical chest pain associated with electrocardiographic ST-segment depression in all 9. The patients received ISDN oral spray or sublingual tablets immediately on termination of exercise. At least 6 hours later another ergometry test was performed and the patients were crossed over to the other drug. ISDN spray relieved pain in all patients at a mean duration of 61.6 +/- 24.4 seconds after administration, whereas the duration of relief of pain by ISDN sublingual tablets was 112.4 +/- 70 seconds. The difference was highly significant (p less than 0.0005). It is concluded that clinical practice of treatment of angina pectoris in the elderly can be improved by using ISDN oral spray rather than sublingual tablets. The spray is effective at twice the rapidity of the sublingual tablet.

Comparison of nitroglycerin-TTS and long-acting nitroglycerin tablets in the treatment of angina pectoris: a double-blind controlled study

A cohort of 99 patients with severe, stable angina pectoris participated in a 26-week double-blind, between-patient trial of a transdermal therapeutic system (TTS) Nitroglycerin-TTS 5 mg/24 h and long-acting nitroglycerin tablets, 10.4 mg daily. The variables registered included daily sublingual nitroglycerin requirement, daily anginal attack rate, exercise test performance with ECG recordings, and a subjective patient evaluation on a visual analogue scale. There were no significant differences in the efficacy of the treatment between the two groups. Nor could we find any difference in the efficacy between the initial single-blind placebo treatment and the active nitroglycerin treatments.

A comparative evaluation of hemodynamic and neurohumoral effects of nitroglycerin and nifedipine in congestive heart failure

Nitroglycerin and nifedipine have been suggested as useful agents in the therapy of congestive heart failure. Because of the rapid action and feasability for sublingual administration of both drugs, their comparative hemodynamic and neurohumoral effects were studied in 12 patients with congestive heart failure. After sublingual nitroglycerin, there was a significant decrease in mean arterial pressure (96 +/- 17 to 90 +/- 15 mm Hg, p less than 0.01), left ventricular (LV) filling pressure (30 +/- 12 to 22 +/- 10 mm Hg, p less than 0.01), right atrial pressure (15 +/- 6 to 10 +/- 5 mm Hg, p less than 0.01) and systemic vascular resistance (21.5 +/- 7.7 to 19.3 +/- 6.2 units, p less than 0.05) and an increase in cardiac index (2.2 +/- 0.6 to 2.4 +/- 0.7 liters/min/m2, p less than 0.05) and LV stroke work index (20.4 +/- 7.0 to 24.5 +/- 8.6 gm-m/m2, p less than 0.01). After sublingual nifedipine, there was also a significant decrease in mean arterial pressure (96 +/- 16 to 89 +/- 14 mm Hg, p less than 0.01) and systemic vascular resistance (22.1 +/- 7.1 to 18.0 +/- 6.1 units, p less than 0.01) and an increase in cardiac index (2.1 +/- 0.6 to 2.4 +/- 0.6 liters/min/m2, p less than 0.01); in contrast to nitroglycerin, this was unaccompanied by significant changes in right- or left-sided filling pressures or LV stroke work index.(ABSTRACT TRUNCATED AT 250 WORDS)

New therapeutic modalities for the treatment of elderly patients with ischemic heart disease

In developing a treatment plan for elderly patients with ischemic heart disease, it is important to appreciate that the pathophysiologic process and aging influence the type of response produced by various drugs. The aging process also alters the way drugs are absorbed, distributed, and eliminated. Each of these variables must be considered in deciding which drugs should be used and how they should be administered.

Haemodynamic effects of combined oral nifedipine and sublingual nitroglycerin in patients with chronic stable angina

We examined the pharmacokinetics of nifedipine after acute and sustained oral therapy and the potential haemodynamic interaction between nifedipine and sublingual nitroglycerin in nine patients with chronic stable angina. Nifedipine pharmacokinetics after a single oral dose and sustained dosing (three times daily for five days) were not significantly different. Single dose nifedipine produced a statistically significant decrease in standing and supine systolic and diastolic blood pressures when compared to placebo. A significant decrease in the supine systolic pressure was observed after sustained nifedipine therapy. Except for this change, other hypotensive effects of nifedipine after sustained therapy were not different to those of placebo, in spite of persistent plasma nifedipine concentrations after repeated dosing. There were no observable correlations between nifedipine haemodynamics and pharmacokinetics in these patients, nor were there any significant haemodynamic interactions between sublingual nitroglycerin with either acute or sustained nifedipine treatment. The transient haemodynamic effects of sublingual nitroglycerin were not potentiated by either acute or sustained nifedipine therapy.

Topical nitroglycerin. A safeguard against pressor responses to tracheal intubation

In order to attenuate the pressor response to intubation of the trachea we have studied the effects of 2% nitroglycerin ointment rubbed on the forehead approximately 12 minutes prior to intubation. A double blind, randomized design was used in 56 consecutive patients. Of these, 30 patients received the ointment while 26 patients formed the control group. The maximum rise in the systolic arterial pressure was significantly lower (p less than 0.001) in the group (7.66 mmHg, 6.2%) as compared to the control group (25.7 mmHg, 20.2%). The rise in arterial pressure persisted for up to 4 minutes in the control group, but lasted for only one minute in the nitroglycerine group. The pulse rate, however, increased in both groups to an equal extent. We have found the application of 2% nitroglycerine ointment to be a safe, inexpensive, comfortable and effective means of attenuating the pressor response to intubation of the trachea.

Influence of skin site on bioavailability of nitroglycerin ointment in congestive heart failure

Nitroglycerin ointment (12.5 to 50 mg) was administered in randomized fashion to three skin sites, arm, chest, or thigh, to compare the hemodynamic effects and bioavailability in nine patients with severe congestive heart failure. Hemodynamic parameters and arterial nitroglycerin concentrations were measured frequently for 12 hours after each application and for 90 minutes after removal of the ointment. During the study, left ventricular filling pressures decreased from control values of 25.0 +/- 8.6 mm Hg (arm), 25.7 +/- 10.9 mm Hg (chest), and 23.7 +/- 8.4 mm Hg (thigh) to 20.4 +/- 8.6 mm Hg, 20.4 +/- 8.5 mm Hg, and 20.0 +/- 7.5 mm Hg; p less than 0.05, less than 0.01, and difference not significant respectively. Peak nitroglycerin concentrations were 5.1 +/- 4.3 ng/ml (arm), 6.2 +/- 6.0 ng/ml (chest), and 4.1 +/- 6.3 ng/ml (thigh). No significant difference was observed in mean arterial pressure, left ventricular filling pressure, right atrial pressure, or nitroglycerin concentration among the sites. These data show that nitroglycerin ointment has similar bioavailability on the arm, chest, or thigh and therefore can be used interchangeably on these skin sites.

Comparison of transdermal nitrate and isosorbide dinitrate in chronic stable angina

The effects of transdermal nitrate (TN) (Transiderm-Nitro TTS, Geigy Pharmaceuticals, one 10 cm2 patch daily) and oral isosorbide dinitrate (ISDN) (Sorbitrate, Stuart Pharmaceuticals, 10 mg three times daily) were compared in a group of 20 patients with chronic stable angina pectoris. Treadmill exercise duration was prolonged from a median time of 365 s to 428 s after ISDN (P less than 0.05), but was unchanged after TN. The difference between the active treatments was not significant. Weekly consumption of glyceryl trinitrate (GTN) increased during treatment with TN from a median value of 5.5 to 6.3 (P less than 0.05). A decrease was observed after ISDN (7.8 to 3.9, P = NS), and the difference between the drugs was significant (P less than 0.01). Systolic arterial pressure was significantly lower during the ISDN than during the TN treatment period in both the supine (135 +/- 5 vs 128 +/- 5 mm Hg; P less than 0.05) and standing positions (134 +/- 5 vs 122 +/- 5 mm Hg; P less than 0.05). No change in weekly attack rate, the degree of ST depression at angina on treadmill testing, or the number of episodes of ST depression recorded during a 24 h period by Holter monitoring was observed after either drug. In this study, an antianginal effect was demonstrated for ISDN but not for TN. It is suggested that the dose of TN may have been inadequate to demonstrate such an effect, and further studies using a higher dose schedule will be required.