Transdermal nitroglycerin patches in angina pectoris. Dose titration, duration of effect, and rapid tolerance

Angina in 2022: Current Perspectives

Angina is the main symptom of ischemic heart disease; mirroring a mismatch between oxygen supply and demand. Epicardial coronary stenoses are only responsible for nearly half of the patients presenting with angina; whereas in several cases; symptoms may underlie coronary vasomotor disorders; such as microvascular dysfunction or epicardial spasm. Various medications have been proven to improve the prognosis and quality of life; representing the treatment of choice in stable angina and leaving revascularization only in particular coronary anatomies or poorly controlled symptoms despite optimal medical therapy. Antianginal medications aim to reduce the oxygen supply-demand mismatch and are generally effective in improving symptoms; quality of life; effort tolerance and time to ischemia onset and may improve prognosis in selected populations. Since antianginal medications have different mechanisms of action and side effects; their use should be tailored according to patient history and potential drug-drug interactions. Angina with non-obstructed coronary arteries patients should be phenotyped with invasive assessment and treated accordingly. Patients with refractory angina represent a higher-risk population in which some therapeutic options are available to reduce symptoms and improve quality of life; but robust data from large randomized controlled trials are still lacking.

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.

Transdermal patches: history, development and pharmacology

Transdermal patches are now widely used as cosmetic, topical and transdermal delivery systems. These patches represent a key outcome from the growth in skin science, technology and expertise developed through trial and error, clinical observation and evidence-based studies that date back to the first existing human records. This review begins with the earliest topical therapies and traces topical delivery to the present-day transdermal patches, describing along the way the initial trials, devices and drug delivery systems that underpin current transdermal patches and their actives. This is followed by consideration of the evolution in the various patch designs and their limitations as well as requirements for actives to be used for transdermal delivery. The properties of and issues associated with the use of currently marketed products, such as variability, safety and regulatory aspects, are then described. The review concludes by examining future prospects for transdermal patches and drug delivery systems, such as the combination of active delivery systems with patches, minimally invasive microneedle patches and cutaneous solutions, including metered-dose systems.

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.

Nitroglycerin rebound associated with vascular, rather than platelet, hypersensitivity

OBJECTIVES

The purpose of this study was to determine whether acute withdrawal of nitroglycerin (NTG) during hemodynamic tolerance is associated with platelet hypersensitivity.

BACKGROUND

Nitroglycerin is an effective antianginal medication but its use is limited by the development of tolerance and rebound. We have previously demonstrated a sustained inhibition of platelet function during continued use of NTG, but whether cessation of NTG is associated with an increase in platelet function that may contribute to rebound is unknown.

METHODS

Normal porcine aortic media were exposed to flowing arterial blood from pigs (n = 8) treated continuously with NTG patches (Nitrodur 0.8 mg/h) for 48 h. Platelet function, blood pressure and the responses to angiotensin II infusion were evaluated before, during and after NTG treatment.

RESULTS

Mean arterial pressure fell by 15% after 3 h of treatment compared with control, returned to baseline by 48 h and increased significantly 2 h after drug removal. Autologous 51Cr-labelled platelet deposition on the aortic media was reduced by 30% after 48 h of continuous NTG administration compared with baseline (p = 0.02) and remained decreased 2 h after cessation of NTG therapy. Platelet aggregation to thrombin decreased in parallel to the decrease in platelet deposition. Blood pressure increase after intravenous injection of 10 microg of angiotensin II was blunted during treatment with NTG but increased significantly 2 h after cessation of nitrate therapy when compared with baseline.

CONCLUSIONS

Supersensitivity of the vessel wall to vasoconstrictors such as angiotensin 11, but not platelet hyperactivity, may contribute to the rebound phenomenon after acute nitrate withdrawal.

Effect of pre-treatment with transdermal glyceryl trinitrate on myocardial ischaemia during coronary angioplasty

OBJECTIVE

In the light of the reported inconsistent anti-ischaemic and antianginal effects of transdermal glyceryl trinitrate, its efficacy and influence on the effects of intracoronary glyceryl trinitrate were examined during coronary angioplasty, which provides a model of controlled, reversible ischaemia.

DESIGN

Double blind, randomised study of the effect of transdermal and intracoronary glyceryl trinitrate on ischaemia during coronary angioplasty.

PATIENTS

40 patients with isolated severe stenosis of the left anterior descending coronary artery.

INTERVENTIONS

Patients were randomised (double blind) to transdermal glyceryl trinitrate (10 mg per day) and placebo, starting four to six hours before angioplasty. After 4 one-minute balloon inflations intracoronary glyceryl trinitrate was injected (0.2 mg) and then 4 further one-minute inflations were performed.

MAIN OUTCOME MEASURES

The time to angina and the time to > 0.2 mV ST shift on surface electrocardiogram (ECG) or intracoronary ECG during the individual inflations.

RESULTS

These times did not significantly differ during initial inflations between transdermal glyceryl trinitrate (27 (11), 25 (9), and 19 (9) s, respectively) and placebo (34 (11), 30 (8), and 21 (7) s. After intracoronary glyceryl trinitrate, they were significantly prolonged compared with the initial values, without differences between patients with transdermal glyceryl trinitrate (37 (10), 30 (8), and 23 (8) s, respectively) or placebo (39 (15), 36 (11), and 28 (12) s). Ischaemic preconditioning was not seen.

CONCLUSIONS

Transdermal glyceryl trinitrate (10 mg per day), unlike intracoronary glyceryl trinitrate, did not alleviate the myocardial ischaemia produced by balloon inflation during coronary angioplasty.

Intermittent or continuous transdermal nitroglycerin: still an issue, or is the case closed?

After a decade of controversy and debate, many experts have now concluded that continuous nitroglycerin patch treatment leads to complete tolerance development and therefore cannot be recommended for any angina patient. This conclusion is largely based on the disappointing results of the large Transdermal Nitroglycerin Cooperative Study, in which continuous patch treatment in doses of 15-105 mg daily failed to increase exercise duration more than placebo after 2 and 8 weeks of treatment. However, other well-designed studies recently reported maintained efficacy during continuous treatment, and the differences in results has remained unexplained. The disagreeing data may be better understood if certain facts are considered: (1) The cooperative study tested a patient population with a very low first-dose treatment response--only 34 seconds (or 10-12%) improvement compared with placebo. At the end of the study, 25% of the patients terminated exercise for reasons other than angina, and a reduced nitrate responsiveness had developed, even in the placebo group. (2) Patients who demonstrate a large first-dose nitrate responsiveness tend to be less susceptible to tolerance development. (3) Even during continuous therapy, maintained efficacy is often observed in exercise tests done 2-5 hours after patch renewal, while typically no effect is seen at the end of the application period. Attenuation of the initial effects is seen with all long-acting nitrate treatment regimens, but the degree of tolerance varies with the patient population, the efficacy parameter (exercise test vs. attack counts), the timing of the efficacy test, the patch dose, and whether or not nitrate-free (-low) intervals are used. In general, intermittent patch therapy is superior to continuous therapy in improving exercise duration, but even continuous therapy may retain some effect. Rebound phenomena do occur but are clinically relevant only in a minority of the patients. Rebound phenomena are not a problem during continuous therapy, which therefore may be of value in patients with frequent and/or nocturnal angina attacks. Patients experiencing angina during exercise only and with low first-dose effects are likely to benefit more from intermittent therapy. Doses of 0.6-0.8 mg/hr (15-20 mg/24 hr) are usually optimal, and the efficacy is comparable with that observed after oral nitrates.

Dissociation of coronary vascular tolerance and neurohormonal adjustments during long-term nitroglycerin therapy in patients with stable coronary artery disease

OBJECTIVES

We sought to examine whether long-term nitroglycerin treatment causes tolerance in large coronary arteries and whether the loss of vascular effects parallels neurohormonal adjustments.

BACKGROUND

Nitroglycerin therapy is associated with increased plasma renin activity and aldosterone levels and a decrease in hematocrit. It is assumed that nitroglycerin tolerance results in part from these neurohormonal adjustments and intravascular volume expansion.

METHODS

Three groups were studied: group I (n = 10), no prior nitroglycerin therapy; and group II (n = 10) and group III (n = 8), 24- and 72-h long-term nitroglycerin infusion (0.5 micrograms/kg body weight per min), respectively. Coronary artery dimensions were assessed using quantitative angiography. Plasma renin activity, plasma aldosterone and vasopressin levels and hematocrit were monitored before and during nitroglycerin infusions.

RESULTS

In group I, increasing intravenous concentrations of nitroglycerin caused a dose-dependent increase of the midportion of the left anterior descending coronary artery (baseline diameter 2.13 +/- 0.07 mm [mean +/- SEM], maximally by 22 +/- 2%) and left circumflex coronary artery (baseline diameter 2.08 +/- 0.07) mm, maximally by 22 +/- 3%). An intracoronary nitroglycerin bolus (0.2 mg) caused no further significant increase in diameter, indicating maximal dilation. In group II (n = 10), the baseline large coronary artery diameter under ongoing nitroglycerin was significantly larger than that in group I (left anterior descending artery 2.61 +/- 0.08 mm, left circumflex artery 2.57 +/- 0.08 mm). Additional intravenous and intracoronary nitroglycerin challenges did not cause further dilation, indicating maximally dilated vessels. At the same time, plasma renin activity, plasma aldosterone and vasopressin levels were significantly increased, and hematocrit significantly decreased. In group III patients, the baseline diameter of the left anterior descending artery and the left circumflex artery did not differ from that in patients without nitroglycerin pretreatment, indicating a complete loss of nitroglycerin coronary vasodilative effects. These patients showed no significant increase in circulating neurohormonal levels but a significant decrease in hematocrit.

CONCLUSIONS

Within 24 h of continuous nitroglycerin treatment, the coronary arteries were maximally dilated despite neurohormonal adjustments and signs of intravascular volume expansion. Within 3 days of nitroglycerin infusion, tolerance developed in the absence of neurohormonal activation. The dissociation of neurohormonal adjustments and tolerance in large coronary arteries indicates that after long-term nitroglycerin treatment, true vascular tolerance, perhaps from an intracellular tolerance step, may have developed.

Contemporary approaches in medical management of patients with stable coronary artery disease

CAD continues to be the principal cause of mortality in the United States, and the largest group of patients with CAD are those with stable angina. Among this group of patients, the most common manifestation of CAD is presence of transient episodes of myocardial ischemia. The presence of transient ischemia and not the severity of angina has been found to be associated with poor clinical outcome in patients with stable CAD. As part of a global treatment strategy for patients with stable CAD, changes in lifestyle and modification of coronary risk factors should be emphasized as an integral part of treatment. Conventional antianginal therapy is quite effective in controlling anginal attacks. Currently, several drugs and therapeutic strategies are available for the treatment of patients with angina (see Table 5). Nitrates are highly effective antianginal drugs with complex beneficial actions in patients with CAD, but their usefulness is limited by development of tolerance during long-term use. When clinically indicated, the use of nitrates should be supplemented with another longer-acting antianginal drug, such as a beta-blocker or a calcium channel blocker. Based on the available data, beta-blockers, when tolerated, seem to be the most effective antianginal drugs for most patients with stable CAD. Beta-blockers are also the most effective anti-ischemic drugs that reduce the magnitude of myocardial ischemia detected during routine daily activities. Calcium channel blockers are also effective vasodilators and good antianginal drugs. The clinician should become familiar with the different actions that this heterogeneous group of drugs has on the heart and vessels. This knowledge allows the clinician to choose the appropriate combination of different antianginal drugs for patients on an individualized basis. It is also critical to develop the treatment strategy by carefully taking into account other associated medical conditions that are frequently encountered in patients with CAD.

Intermittent transdermal nitrates do not improve ischemia in patients taking beta-blockers or calcium antagonists: potential role of rebound ischemia during the nitrate-free period

OBJECTIVES

This study was conducted to determine whether rebound ischemia occurs during nitrate-free periods with intermittent cutaneous nitroglycerin therapy in patients with angina pectoris who are receiving background antianginal therapy.

BACKGROUND

Rebound angina has been suggested to be a complication of the nitrate-free period with long-term cutaneous nitroglycerin therapy given intermittently to prevent tolerance.

METHODS

Fifty-two patients with stable effort angina taking either a beta-adrenergic blocking agent (n = 25) or diltiazem (n = 22) or their combination (n = 5) completed a randomized, double-blind, placebo-controlled crossover study of cutaneous nitroglycerin patches (50 mg). Active or placebo patches were worn for 1 week, applied at 8 AM and removed at 10 PM to provide a 10-h daily nitrate-free (or placebo-free) period. During the last 48 h of each study phase, a Holter monitor was used to detect ischemia.

RESULTS

Only 31 patients experienced ischemia during either phase of the study (23 during the patch-off period). A total of 463 ischemic episodes were recorded: 246 during placebo and 217 during nitroglycerin (p = 0.8, for per patient comparison). The majority (88%) of ischemic episodes were silent. Mean (+/- SEM) duration of ischemia during the total 48-h period was similar during active and placebo phases (35.5 +/- 15.0 min/24 h for active therapy vs. 29.7 +/- 9.8 for placebo, p = 0.8). This was due to an increase in duration of ischemia with active therapy during the patch-off period (46.9 +/- 17.9 min/24 h for active therapy vs. 22.5 +/- 9.2 for placebo, p = 0.07) and a decrease during the patch-on period (27.5 +/- 14.0 min/24 h for active therapy vs. 34.5 +/- 11.0 min/24 h for placebo, p = 0.16). The pattern of diurnal distribution of ischemic episodes differed between active and placebo phases. During placebo there was a nadir in the incidence of ischemia in the overnight patch-off period, with a significantly lower incidence between midnight and 6 AM (25 episodes) compared with the mean number of episodes during the three other 6-h periods (73 episodes, p < 0.001). During the nitroglycerin patch-off period, there was a loss of this overnight nadir, with the same incidence of ischemia between midnight and 6 AM (53 episodes) as the mean number of episodes for the three other 6-h periods (54 episodes).

CONCLUSIONS

The majority of patients taking background antianginal therapy experienced no ischemia during the patch-off period. In the 44% of patients with ischemia during this period, there was a nonsignificant increase in the duration of ischemia with active therapy. Although this result was statistically inconclusive, the change in the distribution of diurnal ischemia offers suggestive evidence that rebound ischemia may be a problem with regard to intermittent cutaneous nitroglycerin.

Ointments and transdermal nitroglycerin patches for stable angina pectoris

Nitroglycerin (NTG) ointment is used for the prophylaxis against angina pectoris, but there are no data to support its effectiveness during long-term therapy. Continuous, once-daily application of isosorbide dinitrate cream produces tolerance with complete loss of efficacy within 1 week. Nitroglycerin patches are very popular and continuous once-daily application is still claimed by some investigators to provide 24 hour antiischemic and antianginal efficacy. This claim is based on data from postmarketing studies in a very large number of patients and placebo-controlled studies in smaller groups of patients from Italy, Yugoslavia, Greece, and Germany. In contrast, studies from the United States, Canada, England, and some centers in Germany have failed to show superiority of patches over placebo during continuous therapy. This controversy was addressed by the NTG cooperative study group, in which a total of 562 patients who were responders to sublingual nitroglycerin were studied. Patients received either placebo or NTG patches delivering low (15-30 mg/24 hr), moderate (45-60 mg/24 hr), or large (75 and 105 mg/24 hr) amounts of NTG. Four hours after the initial application, NTG patches increased exercise duration compared to placebo, but this beneficial effect had disappeared by 24 hours. Furthermore, after 8 weeks of continuous therapy, none of the NTG patches were superior to placebo, whether patients were or were not taking concomitant beta-blockers. Therefore, current opinion is that continuous therapy with NTG patches produces pharmacologic tolerance and is ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)

Transdermal nitroglycerin patch therapy reduces the extent of exercise-induced myocardial ischemia: results of a double-blind, placebo-controlled trial using quantitative thallium-201 tomography

OBJECTIVES

This study prospectively evaluated whether transdermal nitroglycerin patches could limit the extent of exercise-induced left ventricular ischemia as assessed by quantitative thallium-201 tomography.

BACKGROUND

Although antianginal medications are effective at reducing chest pain symptoms in patients with coronary artery disease, there is limited evidence that these agents can also reduce myocardial ischemia.

METHODS

This was a randomized, double-blind, parallel, placebo-controlled trial evaluating nitroglycerin patch therapy in patients in stable condition with angiographic coronary artery disease and no previous myocardial infarction. All patients were weaned from antianginal agents and had a baseline symptom-limited treadmill test followed by thallium-201 tomography. Forty patients with perfusion defects involving > or = 5% of the left ventricle were randomized to receive either intermittent (12 h on/off) active nitroglycerin patch therapy (0.4 mg/h) or placebo. Exercise tomography was repeated a mean (+/- SD) of 6.1 +/- 1.8 days after randomization.

RESULTS

Patients randomized to receive active patch therapy had a significant reduction in their total perfusion defect size (-8.9 +/- 11.1%) compared with placebo-treated patients (-1.8 +/- 6.1%, p = 0.04), which was most apparent in those with the largest (> or = 20%) baseline perfusion defects (-11.4 +/- 13.4% vs. 1.0 +/- 3.6%, respectively, p < 0.02). Furthermore, 7 (33%) of 21 patients receiving active therapy had a > or = 10% decrease in their perfusion defects compared with only 1 (5%) of 19 patients randomized to receive placebo (p = 0.002). Nitrate therapy did not significantly reduce heart rate, blood pressure or double product, indicating benefit through enhancement of coronary blood flow.

CONCLUSIONS

Short-term, intermittent nitroglycerin patch therapy significantly reduces myocardial ischemia, particularly in patients with large ischemic perfusion defects. Thallium-201 tomography can be used to assess sequential changes in the extent of exercise-induced left ventricular ischemia.

Efficacy of intermittent (eight hours off) transdermal nitrate therapy in stable angina

The efficacy of intermittent (16 h on/8 h off) transdermal nitrate therapy (0.4 mg/h) was assessed in 46 patients with chronic stable angina, all but one of whom were on concomitant beta-blocker and/or calcium antagonist therapy. The study was a randomised, double-blind placebo-controlled crossover with two consecutive 7-day treatment periods, conducted at two centres. Prior to entry into the study patients were screened for exercise test reproducibility and nitrate response. Patch efficacy was determined by maximal symptom limited treadmill stress testing (Bruce protocol) and subjective diary card data. Analysis of variance showed that active treatment significantly improved time to onset of angina (P < 0.001), time to 1 mm ST-segment depression (P < 0.001) and total exercise duration (P < 0.001) compared with placebo from 385.7, 310.8 and 458.1 s to 455.7, 385.2 and 497.1 s, respectively. Nitrate patch therapy significantly reduced diastolic and systolic blood pressures without significantly increasing resting heart rate. There was a marginal reduction in the incidence of angina attacks and sublingual nitroglycerine consumption during active treatment. We conclude that intermittent transdermal nitrate therapy significantly improves exercise tolerance in patients with chronic angina pectoris and that this improvement occurs in addition to conventional anti-anginal therapy.

Effect of therapy with an angiotensin-converting enzyme inhibitor on hemodynamic and counterregulatory responses during continuous therapy with nitroglycerin

OBJECTIVES

We sought to characterize the reflex counterregulatory responses throughout a 6-day period of continuous nitroglycerin therapy and to examine the effect of concurrent administration of a non-thiol angiotensin-converting enzyme inhibitor (benazepril) on the nature of those responses.

BACKGROUND

Therapy with nitroglycerin has been shown to be associated with reflex counterregulatory responses.

METHODS

Standing systolic blood pressure, hormonal responses, urinary sodium and hematocrit levels were monitored during 6 days of continuous transdermal nitroglycerin therapy in normal volunteers. Using a double-blind randomized parallel design, 11 subjects received placebo and 9 received benazepril. Hemodynamic responses to sublingual nitroglycerin administration were evaluated before and after sustained therapy with transdermal nitroglycerin.

RESULTS

Attenuation of the hypotensive response to transdermal nitroglycerin was rapid in the group receiving placebo and the group receiving benazepril. There were no significant hormonal responses to transdermal nitroglycerin in either group, and sodium retention was modest and transient. Hematocrit levels decreased after transdermal nitroglycerin therapy and remained depressed for the duration of nitroglycerin therapy, a finding that suggests plasma volume expansion. Blood pressure responses to sublingual nitroglycerin in both groups were similar before and after continuous transdermal nitroglycerin therapy.

CONCLUSIONS

These data suggest that plasma volume expansion plays a more important role than neurohormonal responses in the loss of nitrate effects during sustained therapy. That therapy with an angiotensin-converting enzyme inhibitor did not modify the hemodynamic responses to continuous nitroglycerin therapy supports this conclusion. Further investigation will be necessary to confirm whether therapy with an angiotensin-converting enzyme inhibitor has any role in the prevention of nitrate tolerance.

Lack of rebound during intermittent transdermal treatment with glyceryl trinitrate in patients with stable angina on background beta blocker

OBJECTIVE

To assess whether intermittent transdermal treatment with glyceryl trinitrate causes clinically significant rebound in patients maintained on beta blockers for stable angina pectoris.

DESIGN

Serial treadmill exercise testing in a double blind, randomised, placebo controlled cross over trial. Baseline exercise testing was performed at 0900 and 1100 at visit 1. Transdermal glyceryl trinitrate patches releasing 15 mg/24 h were applied at 2200 the evening before visits 2 and 3, and exercise testing was performed at 0900 the next morning. The patch was removed and replaced with either an identical patch or matching placebo and exercise tests were repeated two hours later. The alternative treatment was given at visit 3.

SETTING

Tertiary referral centre.

PATIENTS

14 patients with stable angina pectoris maintained on beta blocker treatment alone.

MAIN OUTCOME MEASURES

Time to angina, 1 mm ST segment depression, and total time, together with heart rate, systolic blood pressure, and rate-pressure product.

RESULTS

Active treatment improved treadmill performance at 0900 and 1100. Time to angina, time to 1 mm ST segment depression, and total time fell significantly on placebo compared with the 0900 exercise test on active treatment, but were not significantly different to the baseline exercise test either.

CONCLUSIONS

Intermittent transdermal treatment with glyceryl trinitrate is not associated with the rebound phenomenon in patients maintained on beta blockers for stable angina pectoris.

The effect of transdermal nitroglycerin on exercise tolerance in relation to patch application time--a meta-analysis

Disagreeing results have been reported in the many studies on continuous treatment with nitroglycerin patches. The effects on exercise tolerance are partly studied at the end of a 24-hour application period, and partly examined only a few hours after patch renewal. The present meta-analysis estimates the overall efficacy of nitroglycerin patches in trials with and without concomitant antianginal therapy, and investigates if the treatment effect depends on the patch application time. A computed search (MEDLINE) identified 110 publications, of which 17 trials on nitrate patch monotherapy and six trials on combined therapy satisfied the inclusion criteria. Data on "exercise duration" and "ST-segment depression" were converted to a standardized treatment effect size d, and pooled to an overall treatment effect size d+. In tests 2-5 hours after patch renewal, moderate but significant effects of nitrate monotherapy were observed; d+ was 1.20 with regard to "ST-segment depression" and 0.39 with regard to "exercise duration" (both p < 0.0001). In contrast, 24 hours after patch application, the values for d+ were 0.09 (not significant) and 0.36 (p < 0.01), respectively. When adding the results from the six trials on combined therapy, d+ with regard to "exercise duration" was reduced to 0.28 (p < 0.0001) 2-5 hours after renewal and to 0.17 (p = 0.04) after 24 hours. Thus, the efficacy of continuous nitroglycerin patch treatment is moderate but evident during exercise tests 2-5 hours after patch renewal; however, it is reduced after 24 hours of patch application.

Efficacy of isosorbide mononitrate in angina pectoris

The rapid development of tolerance has limited the applicability of oral and transdermal nitrates in the long-term management of patients with chronic stable angina pectoris. Recent well-controlled trials have demonstrated that asymmetrical, or eccentric, dosing of oral isosorbide mononitrate, in which 20-mg doses are taken at 8 A.M. and 3 P.M., provides at least 12 hours of antianginal coverage. There is no evidence for the development of tolerance with this schedule, which allows for a 17-hour nitrate withdrawal period. Likewise, the asymmetrical 20-mg twice daily regimen has not been associated with the zero-hour effect that has been reported with higher oral doses of isosorbide mononitrate and with intermittent nitroglycerin patch therapy. This approach also avoids the development of a clinical rebound phenomenon, as measured by increased episodes of angina and nitroglycerin consumption, compared with the pretreatment period, during the nitrate-free interval at night and the early hours of the morning.

Role of nitrates in angina pectoris

Nitrates are used extensively for the treatment of angina pectoris. However, continuous therapy with either oral nitrates or nitroglycerin patches leads to rapid development of tolerance, with loss or diminution of antianginal and anti-ischemic effects. The only practical way to avoid the development of tolerance is to use intermittent daily therapy with nitrates. Nitroglycerin patches applied for 10-12 hours during the day increase exercise duration for 8-12 hours, but a rebound increase in anginal attacks during the nitrate-free interval may occur. Oral isosorbide-5-mononitrate, 20 mg twice a day, with the first dose administered in the morning and the second dose 7 hours later, increases exercise duration for at least 12 hours without the development of tolerance to either the morning or afternoon dose. This dosing regimen has been shown not to produce a rebound phenomenon during the periods of low nitrate levels at night and early hours of the morning. Isosorbide dinitrate (30 mg) prescribed at 7 AM and 1 PM does not produce tolerance to the 7 AM dose, but effects of the afternoon dose have not been evaluated. Recent data suggest that isosorbide dinitrate given 3 or 4 times daily produces tolerance and this dosing schedule is inadequate for antianginal prophylaxis. It should be recognized that intermittent oral or patch therapy with nitrates during the day leaves the patient unprotected at night and early hours of the morning. If this is of concern, additional therapy with another class of antianginal agent, preferably a long-acting beta blocker or a long-acting calcium antagonist should be instituted.

Effects of diuretic therapy on the development of tolerance during continuous therapy with nitroglycerin

OBJECTIVES

This study examined the effects of concurrent diuretic therapy on the hemodynamic responses to short-term and sustained therapy with transdermal nitroglycerin.

BACKGROUND

Sodium retention and plasma volume expansion occur during therapy with nitroglycerin and may play a role in the loss of nitroglycerin effects during sustained therapy.

METHODS

Twenty-two normal male volunteers were treated for 1 week with either hydrochlorothiazide and amiloride (50 + 5 mg) (n = 11) or placebo (n = 11) in a randomized, double-blind fashion. All 22 subjects then received continuous transdermal nitroglycerin (19 +/- 1 mg/24 h) for 5 to 7 days.

RESULTS

On the first and last day of transdermal nitroglycerin therapy, standing heart rate, systolic blood pressure and hematocrit values were assessed at 8, 9 and 10 AM and 12 noon. Heart rate and blood pressure responses to sublingual nitroglycerin (0.6 mg) were also evaluated before and after sustained transdermal nitroglycerin therapy. A significant loss of the hemodynamic effects of transdermal and sublingual nitroglycerin occurred during sustained therapy in both the diuretic and placebo therapy groups. In both groups, transdermal nitroglycerin therapy was associated with a significant decrease in hematocrit that persisted for the entire treatment period.

CONCLUSIONS

These results suggest that diuretic therapy does not prevent plasma volume expansion or the loss of hemodynamic effects during sustained transdermal nitroglycerin therapy. The persistent decrease in hematocrit suggests that plasma volume expansion plays a role in the attenuation of nitrate effects. It also provides evidence of continued vascular activity of nitroglycerin despite loss of systemic hemodynamic effects.

Effects of 8:00 a.m. and 2:00 p.m. doses of isosorbide-5-mononitrate during twice-daily therapy in stable angina pectoris

"Trough" plasma concentrations of isosorbide-5-mononitrate (IS-5-MN), an active metabolite of isosorbide dinitrate, of less than 95 ng/ml are considered necessary to prevent development of tolerance to isosorbide dinitrate and IS-5-MN. In a double-blind, crossover, placebo-controlled study, the effects of IS-5-MN during twice daily eccentric therapy were evaluated in 18 patients with reproducible exercise-induced angina who were nitrate responders. In a random order, patients received either placebo or IS-5-MN (20 mg) at 8 a.m. and 2 p.m. for 1 week each. Average trough plasma IS-5-MN concentrations before the 8 a.m. and 2 p.m. doses were 67 and 226 ng/ml, respectively, and increased to 382 and 488 ng/ml 2 hours after the 8 a.m. and 2 p.m. doses, respectively. Despite a more than threefold higher trough plasma IS-5-MN concentration before the 2 p.m. dose than before the 8 a.m. dose, the increase in exercise duration 2 hours after the doses was similar (1.21 minutes [21%] after 8 a.m. dose, and 1.08 minutes [19%] after 2 p.m. dose). These increases in exercise duration after IS-5-MN were significantly (p less than 0.01) greater than those observed after placebo (0.17 minutes [3%] after 8 a.m. dose, and -0.05 minute [-0.5%] after 2 p.m. dose). Reduction in standing systolic blood pressure at 2 hours after the doses was also nearly identical after the 8 a.m. and 2 p.m. doses of IS-5-MN (21 [15%] and 19 [14%] mm Hg, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Nitrate tolerance. How to prevent it or minimize its effect

Continuous therapy with nitrates rapidly produces tolerance along with loss or diminution of circulatory, antianginal, and anti-ischemic effects. Development of tolerance can be avoided by various approaches. In patients with stable angina, intermittent use of nitrates with long nitrate-free intervals, use of transdermal nitroglycerin during the day or oral isosorbide dinitrate or isosorbide-5-mononitrate twice daily in the morning and early afternoon, and intermittent use of nitrates in combination with another class of antianginal agent are appropriate. In patients with unstable angina, continuous therapy with intravenous nitroglycerin is recommended during the acute phase of angina. Despite development of partial tolerance, oral isosorbide dinitrate, 30 to 60 mg four times a day, plus hydralazine may be useful for patients with congestive heart failure who cannot tolerate angiotensin-converting enzyme inhibitors. Concomitant use of sulfhydryl donors or angiotensin-converting enzyme inhibitors, agents that might theoretically prevent nitrate tolerance, is not recommended. Data on these agents are conflicting, and added costs and adverse effects are likely to preclude their use in the future.

Pharmacodynamic and pharmacokinetic evaluation of a new transdermal delivery system with a time-dependent release of glyceryl trinitrate

The pharmacokinetics of glyceryl trinitrate (GTN) and its main metabolites as well as the hemodynamic effects of a new transdermal delivery system (TDS) were investigated in ten healthy male volunteers using a single blind, placebo-controlled study design with an application period of active drug of 4 successive days. The adhesive-type matrix system contains 20-mg GTN and released about 75% in a time-dependent manner. The plasma concentrations of GTN and its metabolites 1-2- and 1-3 glyceryl dinitrate reflected the time-dependent release with higher plasma concentrations during the first 12 hours than during the second 12 hours. Continuous administration of the TDS, which released 15 mg GTN/day, caused an accumulation of GTN in the plasma (about 70% greater AUC at the fourth day in comparison with the first day). The total effect per dose on the a/b-ratio of the digital pulse (height of the peak of the systolic wave divided by height of the peak of the dicrotic wave) and the reflex tachycardia were diminished by about 50% and 37%, respectively, at the fourth treatment day. The effect on systolic blood pressure measured under orthostatic conditions was blunted already 8 hours after the first application. The effect of sublingually administered GTN on digital pulse was attenuated during administration and also 1 hour after removal of the last TDS. The effect was restored 8 to 12 hours after removal of the TDS. Thus, the discontinuous release of GTN from the new system does not prevent the decline of hemodynamic efficacy during continuous therapy.

Counter-regulatory responses to continuous and intermittent therapy with nitroglycerin

BACKGROUND

Vasodilator therapy may be associated with reflex counter-regulatory responses, and these responses may play a role in the development of tolerance to nitroglycerin (GTN).

METHODS AND RESULTS

Standing systolic blood pressure, body weight, urinary sodium, and hormonal responses to continuous (n = 10) and intermittent (n = 10) transdermal GTN administration were studied in normal volunteers. There was rapid attenuation of the hypotensive response to transdermal GTN therapy in the continuous but not in the intermittent therapy group. Significant weight gain and sodium retention occurred during continuous but not during intermittent GTN therapy. This was accompanied by a greater decrease in hematocrit in the continuous group, a finding that suggests that plasma volume expansion occurred during continuous GTN therapy. Continuous GTN therapy was associated with increases in plasma norepinephrine, atrial natriuretic peptide, arginine, vasopressin, and plasma renin activity. A different pattern of neurohormonal response was seen during intermittent therapy, with values tending to return to baseline levels after the nitrate-free interval.

CONCLUSIONS

Continuous transdermal GTN therapy leads to counter-regulatory responses associated with sodium retention and probable plasma volume expansion. By contrast, intermittent transdermal GTN therapy is associated with a different pattern of hormonal response, the lack of sodium retention and no evidence of plasma volume expansion. It is likely that these counter-regulatory responses play an important role in the attenuation of nitrate effects.

Acute and chronic antianginal efficacy of continuous twenty-four-hour application of transdermal nitroglycerin. Steering Committee, Transdermal Nitroglycerin Cooperative Study

To resolve the controversies surrounding the antianginal use of chronic, continuous 24-hour transdermal nitroglycerin therapy, a double-blind, placebo-controlled, randomized, parallel-group study was designed. Eligible patients had chronic angina pectoris with symptom-limited, reproducible treadmill tests and were responsive to sublingual nitroglycerin (n = 562). Patients were randomly assigned to placebo or 1 of 7 doses of active treatment (15, 30, 45, 60, 75, 90 and 105 mg/24 hours). In the active drug groups, treatment was initiated with 15 mg/24 hours during the first week of double-blind dosing with subsequent weekly increases until the assigned dose was reached, after which the dose was held constant. Treadmill tests were performed 0, 4 and 24 hours after the initial double-blind patches were applied, after each titration step and after 8 weeks. At the end of double-blind therapy, a sublingual nitroglycerin exercise challenge was repeated. Exercise tolerance in patients using the active patch increased 34 seconds (p less than 0.05) over patients taking placebo 4 hours after the initial application of double-blind therapy, but there was no statistically significant difference in exercise time between placebo and active drug groups by 24 hours after the first application or for the remaining 8 weeks of the trial. Increasing the dose did not overcome the loss of effect. A partial attenuation of the response to a sublingual nitroglycerin challenge seen on exercise tolerance testing also occurred, with patients who received the highest dose showing the greatest attenuation. There were no differences in angina frequency among the groups, although in a post hoc analysis, patients with greater than 7 attacks per week had a reduction in anginal frequency of 6 to 7 attacks per week with active treatment versus 2 attacks per week with placebo. The study showed that (1) tolerance to the exercise effects of continuous transdermal nitroglycerin develops within 24 hours after application; and (2) increasing the dose does not overcome this tolerance. The observation that symptomatic improvement may occur in the absence of increases in exercise tolerance seems deserving of further study.

Long-term efficacy of continuous and intermittent use of transdermal nitroglycerin in stable angina pectoris

To assess efficacy of transdermal nitrate use, a randomized, placebo-controlled trial of continuous and intermittent use of nitroglycerin patches (10 mg/24 hours) was conducted in 127 patients with stable angina pectoris who discontinued exercise testing within 9 minutes because of angina. After a placebo run-in week, baseline (day 0) symptom-limited exercise testing was performed and repeated on day 1 and 14 before and after the administration of 0.5 mg of sublingual nitroglycerin. On day 0, total exercise duration was the same (within narrow limits) in all 3 groups and remained unchanged in the placebo group. On day 1, total exercise duration increased from 406 +/- 115 to 469 +/- 158 seconds (p less than 0.001) in the continuously treated group and from 396 +/- 105 to 475 +/- 171 seconds (p less than 0.001) in the intermittently treated group. In the intermittent group, exercise duration increased slightly to 483 +/- 140 seconds on day 14, and in the continuous group exercise duration decreased to 447 +/- 144 seconds. However, this decrease was not statistically significant. Similar treatment effects were seen for time to 1-mm ST depression. Sublingual nitroglycerin remained effective in all 3 groups and on all days. Eleven actively treated patients and 1 patient taking placebo discontinued the study because of headache. It is concluded that continuous use of transdermal nitroglycerin remains partially effective and intermittent therapy remains fully effective in improving long-term exercise capacity with acceptable adverse effects in patients with stable angina pectoris.

Avoidance of tolerance and lack of rebound with intermittent dose titrated transdermal glyceryl trinitrate. The Transdermal Nitrate Investigators

OBJECTIVES

To investigate the efficacy of transdermal glyceryl trinitrate given continuously and with a nocturnal nitrate free period.

DESIGN

Double blind placebo controlled study with two parallel limbs.

SETTING

Multicentre trial.

PATIENTS

52 patients randomised to receive either continuous treatment (23 patients) or intermittent treatment with an individually titrated dose (29 patients) for 14 days: both treatments were compared with placebo in a cross-over fashion.

INTERVENTION

Continuous treatment with 10 mg per 24 hours of transdermal glyceryl trinitrate or intermittent transdermal glyceryl trinitrate titrated to give an arbitrary 10 mm Hg drop in systolic blood pressure (mean dose 18.2 mg) given over approximately 16 hours.

MAIN OUTCOME MEASURE

Treadmill exercise stress testing and ambulatory monitoring of the ST segment after 14 days' treatment.

RESULTS

After 14 days' intermittent treatment resting supine and standing systolic blood pressure fell by 7.5 mm Hg (95% confidence interval 2.7 to 12.2) and 9.0 mm Hg (95% CI 3.4 to 14.5) respectively (p less than 0.01); resting heart rate was unchanged. Mean heart rate at 1 mm ST segment depression rose by 11.9 beats/min (CI 1.1 to 23.7) (p less than 0.05), mean time to onset of angina increased by 59 seconds (CI 10.8 to 108) (p less than 0.05), and total exercise duration increased by 40 seconds (p less than 0.05). These changes were not seen after continuous treatment. The frequency of ischaemic episodes was not reduced with either regimen nor was the circadian distribution of these episodes altered, in particular nocturnal episodes did not increase during intermittent treatment.

CONCLUSION

Tolerance to glyceryl trinitrate was avoided by the use of individually titrated doses administered with a nocturnal nitrate free period. There was no evidence of "rebound" on ambulatory monitoring during this treatment.

Efficacy of continuous and intermittent transdermal treatment with nitroglycerin in effort angina pectoris: a multicentric study. The Collaborative Nitro Group

Eighty-eight patients (84 men and 4 women; mean age 59.3 years) with stable exercise-induced angina pectoris were enrolled in this within-patient, placebo-controlled study aimed at comparing the efficacy of the continuous and intermittent (12 hour on, 12 hour off) application of transdermal nitroglycerin. Eighty-one patients completed the study. After a 1-week placebo run-in period, during which the stability of angina was assessed on a bicycle ergometer, the patients received continuous treatment (two 10 mg/24 hour patches twice daily, at 8 a.m. and 8 p.m.), intermittent treatment (two 10 mg/24 hour patches at 8 a.m. and two placebo patches at 8 p.m.) and placebo (two placebo patches twice daily, at 8 a.m. and 8 p.m.), each given for one week in a double-blind randomised sequence, according to a 3 x 3 latin-square design. A cycloergometric exercise test was performed at the end of each period of treatment, 4 and 10 hours after the application of the morning patch. In comparison with placebo, both schedules of the active treatment induced a significant increase in both the ischemic (duration of exercise to 1 mm ST segment depression) and the angina threshold (duration of exercise to mild angina) at the 4th and at the 10th hours after-dosing. A significant difference was also found between continuous and intermittent treatment at the same times of observation, in favour of the intermittent schedule. The limited number of anginal attacks recorded during placebo prevented any clinical evaluation of the treatments. This study shows that the efficacy of transdermal nitroglycerin is more pronounced when it is given following an intermittent schedule.(ABSTRACT TRUNCATED AT 250 WORDS)

The day-long antianginal effectiveness of nitroglycerin patches. A double-blind study using dose-titration

This study was designed to determine the day-long antianginal effectiveness of nitroglycerin patches in the nitrate-exposed patient, as well as the doses required. Eight men with chronic stable angina, a positive treadmill test, and demonstrated responsiveness to long-term oral isosorbide dinitrate were studied after they had been taking effective doses of isosorbide dinitrate three times a day for at least two weeks. Treadmill exercise bouts were performed every 1 to 2 hours over 1 day, after the 8 am application of active nitroglycerin patches in a previously titrated dose, and on another day after application of placebo patches. Mean necessary effective patch dose was 125 sq cm (60 to 220 sq cm). Mean exercise duration to angina rose from 271 to 480 s (p less than 0.001) 1 hour after active patches, while resting systolic blood pressure fell from 122 mm Hg to 100 mm Hg (p less than 0.001). (After placebo patches: +19 s and -2 mm Hg, respectively.) Active patches were superior to placebo throughout the day, but in declining degree (by 94 s at 7 pm, p less than 0.05). Thus, nitroglycerin patches can provide a significant day-long antianginal effect in the patient with long-term exposure to nitrate. However, the need for large doses and individual titration may make this therapy impractical.

Prevention of nitrate tolerance with angiotension converting enzyme inhibitors

BACKGROUND

Activation of neurohumoral hormones or sulfhydryl group depletion may contribute to the development of nitroglycerin tolerance. In an attempt to prevent nitrate tolerance, this study evaluated the interaction of nitroglycerin with angiotensin converting enzyme (ACE) inhibitors with and without a sulfhydryl group.

METHODS AND RESULTS

Thirty-four subjects were randomized to a 7-day regimen of enalapril 10 mg b.i.d., captopril 25 mg t.i.d., or placebo. Venodilator response to nitroglycerin was assessed with forearm plethysmography by measuring the change in venous volume after administration of 0.4 mg sublingual nitroglycerin. Plethysmographic measurements were obtained serially 1) at baseline, 2) after 4 days of ACE inhibitor or placebo, 3) 2 hours after application of a 10 mg/24 hr nitroglycerin patch, and 4) 74 hours after continuous nitropatch application. ACE inhibition alone caused no significant change in the response to sublingual nitroglycerin. Nitrate response remained unchanged after 2 hours ("acute") of nitropatch exposure in all three groups. After 74 hours ("chronic") of continuous nitropatch application, the venodilator response to sublingual nitroglycerin was reduced by 40% in the placebo group, 10% in the enalapril group, and 2% in the captopril group. This attenuation was significant only in the placebo group (p less than 0.01). Pairwise comparison of nitrate response between groups was significantly different between the captopril and placebo groups (p less than 0.01) and between the placebo and enalapril groups (p less than 0.05). Plasma renin levels increased equally in the enalapril and captopril groups. Body weight increased only in the placebo group, suggesting prevention of nitrate-induced volume expansion in the ACE inhibitor groups.

CONCLUSIONS

This study demonstrates that ACE inhibitors may prevent nitrate tolerance to long-term nitrate therapy.

Methionine restores the venodilative response to nitroglycerin after the development of tolerance

Depletion of sulfhydryl groups may contribute to nitroglycerin tolerance after long-term exposure. This study was performed to assess whether methionine, an amino acid capable of augmenting sulfhydryl availability, would restore the venodilative response to sublingual nitroglycerin once tolerance had developed. The venodilative response to organic nitrates was assessed with use of the equilibration technique of forearm plethysmography. Venous volume was measured before and after sublingual administration of 0.4 mg of nitroglycerin at baseline study and after 5 g of intravenous methionine. Retesting was performed 2 h after application of a 10 mg nitroglycerin patch and compared with the response after 74 h of nitroglycerin patch exposure before and after intravenous methionine. Methionine alone had no intrinsic venodilative action. Although the venous volume at rest was unchanged after methionine administration, the response to sublingual nitroglycerin was potentiated compared with baseline values (37 +/- 15% versus 32 +/- 13%, p less than 0.02). During nitroglycerin patch exposure, the response to sublingual nitroglycerin was significantly attenuated at 74 h compared with the response at 2 h of exposure (16 +/- 10% versus 31 +/- 13%, p less than 0.001). The venodilative response to sublingual nitroglycerin was restored at 74 h after methionine administration (35 +/- 14% versus 16 +/- 10%, p less than 0.001). Thus, methionine potentiates the venodilative effect of sublingual nitroglycerin both immediately and in the setting of nitrate tolerance.

The hazards of defibrillation through nitroglycerin patches

A case is presented in which defibrillation produced a small explosion in a nitroglycerin patch over which a paddle had been placed. Arcing of the electrical current from the aluminum backing on the patches was the likely cause, but arcing has also occurred with nitroglycerin ointment and electrode gel. All patches and ointments should be removed from the chest of patients about to undergo defibrillation.

Clinical efficacy of current transdermal drug delivery systems: a retrospective evaluation

In spite of intensive research on transdermal drug delivery systems (TDDSs), only four--nitroglycerin, clonidine, estradiol, and scopolamine--have reached the market, and the clinical effectiveness of these systems has yet to be clearly demonstrated. Ideally, a candidate for transdermal drug delivery should demonstrate clinical significance within a wide therapeutic range for a well-documented indication for use. Continuous administration of a drug should result in better control of the disease with fewer side effects and a marked increase in patient compliance than when traditional dosage forms are used. It appears that nitroglycerin is a poor candidate for transdermal drug delivery by virtue of the ambiguity associated with its clinical pharmacology, substantial interpatient variation in dose-response relationship, and development of tolerance with potential toxicity risks in chronic administration. Clonidine's well-defined indication for use coupled with its high potency and low molecular weight with high lipid solubility is well suited to transdermal therapy. Because estradiol is unsuitable for use in people who smoke and has dermatotoxic potential, it is a marginal candidate for use in TDDSs. Transdermal scopolamine was not reviewed because it is a unique entity (no conventional dosage forms of this product are available) intended for short-term use. Its use is dictated more by the patient's unique circumstances, such as travel requirements, than by physiological condition. Although TDDSs provide a convenient and effective means of administering medications, the aforementioned clinical constraints need to be evaluated in depth before more widespread application of TDDSs can be recommended. In particular; conclusive demonstration of biocompatibility of a TDDS is warranted.

The daylong pattern of the antianginal effect of long-term three times daily administered isosorbide dinitrate

Three times daily administration of isosorbide dinitrate may avoid much of the tolerance seen with more frequent dosing. To determine the daylong pattern of the antianginal effect of three times daily isosorbide dinitrate, eight men with stable exertional angina and a positive exercise test were studied. The subjects had demonstrated increased exercise duration in response to oral isosorbide dinitrate therapy and absence of complete tolerance to long-term three times daily isosorbide dinitrate. Treadmill exercise to onset of angina was performed over 2 days at 8 AM, 9 AM, 11 AM, 1 PM, 2 PM, 4 PM, 6 PM and 7 PM. On one day each patient received isosorbide dinitrate at 8 AM, 1 PM and 6 PM in a previously titrated dose (mean 27.5 mg), which had been taken three times daily for at least 2 weeks. On the other day at the same hours each patient received double blind a placebo identical in appearance to isosorbide dinitrate. One hour after the 8 AM dose of isosorbide dinitrate, mean systolic blood pressure at rest had fallen by 19 mm Hg and mean exercise time to angina increased by 200 s. However, by 11 AM exercise time had returned to control level. One hour after the 1 PM dose of isosorbide dinitrate, exercise time increased by a mean of 150 s but was again at control level 2 h later.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina: evolution of the role of nitrates

In recent years, concern has been expressed over attenuation of therapeutic effect in patients receiving continuous nitroglycerin therapy for the treatment of angina. Studies have shown that exercise tolerance time does not improve with continuous nitroglycerin regimens, although the frequency of anginal attacks may decrease. Intermittent therapy, which incorporates a nitrate-free interval, improves both exercise time and clinical angina. The optimal duration of the nitrate-free interval has yet to be determined. Future research is likely to focus more on supply-side factors in angina. Of the available antianginal drugs, nitrates have been shown to be highly effective coronary vasodilators, particularly in areas of stenosis.

Long-term efficacy of nitroglycerin patch in stable angina pectoris

Subchronic and chronic efficacy of a 10 mg of nitroglycerin (NTG) patch was studied in 30 patients with stable angina pectoris. The trial consisted of 2 periods of study: 1 period of 2 months with a double-blind, crossover, placebo-controlled design and a second period of open treatment with verum patch. Two 7-day washout periods were performed at entry and at the end of the study. Efficacy was evaluated by clinical assessment of anginal attacks and NTG consumption and by means of multistage treadmill exercise testing. Exercise tests were performed at time 0 (24 hours from application of last patch), at 4 and 12 hours after dosing at the end of first 7-day washout, at the end of the first month of treatment, at the end of the second month of treatment after crossover, at the end of 3 months of treatment with active patch and at the end of the second 7-day washout period. Statistics were obtained by multivariate analysis of difference. In 27 patients whose records were available for final analysis the daily attacks of angina and NTG consumption decreased significantly during both the subchronic and chronic phases of the trial compared with placebo (p less than 0.001). Subchronic study showed significant improvement of maximal exercise duration, time to onset of angina, time to ST-segment depression of 1.0 mm, time to regression of angina and time to regression of ST depression, compared with placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of a controlled-release formulation of isosorbide-5-mononitrate and conventional isosorbide dinitrate on exercise performance in men with stable angina pectoris

Thirty-three men with stable exercise-induced angina pectoris entered a randomized, double-blind, crossover study in which controlled-release isosorbide-5-mononitrate 60 mg once daily was compared with conventional isosorbide dinitrate 20 mg 3 times daily. Each drug was given for 2 weeks. Twenty-eight patients completed the study and data on exercise variables are available in 23 patients. Treatment with either drug resulted in significant antianginal effects, when measured 6 hours after a single dose and after 2 weeks of therapy compared with baseline placebo; however, there were significantly fewer signs of myocardial ischemia during treatment with isosorbide-5-mononitrate. There was no evidence of tolerance to either drug treatment but a significant attenuation of resting blood pressure (but not of exercise blood pressure) was observed with both drugs. Headache was the only clinically significant adverse event during therapy and it occurred more frequently in the isosorbide dinitrate treatment group (p less than 0.05 vs placebo); 3 such patients had to withdraw from the study because of headache. Thus, once-daily, controlled-release isosorbide-5-mononitrate appears as effective as conventional isosorbide dinitrate 3 times daily in patients with stable angina pectoris. The once-daily administration is convenient and improves patient compliance.

A novel differentiation method of vehicle models for topically applied drugs: application to a therapeutic timolol patch

A novel method to differentiate basic vehicle models for topically applied drugs is proposed. In this method, the rate of drug release as a function of time, obtained by using a flow-through cell, is plotted on both semilogarithmic and logarithmic scales. In the Solution Case, where all of the drug is dissolved in the vehicle, the profiles become linear on the semilogarithmic scale. However, in the Suspension Case, where the initial drug amount per vehicle volume is greater than the solubility of the drug and the vehicle contains finely dispersed drug, the profiles are linear on the logarithmic scale with a slope of -0.5. They abruptly depart from this pattern upon depletion of the suspended phase. The different attributes of the profiles for the drug release rate-time curves in these two cases can be visualized more clearly when vehicle thickness and drug concentration are varied. The theoretical principles are illustrated in profiles for the drug release-rate time plots of therapeutic patches containing the beta blocker timolol. This was formulated at different concentrations in an acryl copolymer with varied thickness. The release profiles were best fitted to the Solution Case treatment of the data.

Mechanisms of nitrate tolerance: a review

With the increased use of long-acting nitroglycerin preparations, there has been greater recognition of the problem of nitrate tolerance. In recent years extensive research has broadened our understanding of the mechanisms of nitroglycerin action and the mechanisms of drug attenuation. This paper reviews the current state of knowledge regarding nitroglycerin tolerance, with an emphasis on the concepts of cellular and neurohumoral mechanisms of drug attenuation. The discussion includes potential approaches to prevent nitrate tolerance, including the introduction of a nitrate-free interval, or concomitant administration of sulfhydryl donors or neurohumoral blocking agents.

Nitrate tolerance. A problem during continuous nitrate administration

The organic nitrates are effective agents in the management of patients with angina pectoris. They are the agents of choice in the treatment of acute episodes of angina pectoris and are useful in angina prophylaxis. While the organic nitrates are extremely effective in angina prophylaxis during acute therapy, there is increasing evidence that with many dosing regimens for oral and transdermal therapy, substantial attenuation of the antianginal effects develops. Thus, during acute therapy the organic nitrates improve exercise tolerance for many hours, but during sustained therapy designed to provide antianginal efficacy throughout the 24-h period there is significant attenuation of the beneficial effects. It has been documented that treatment regimens designed to provide a period of nitrate washout prevent or reverse nitrate tolerance, and such changes in dosing regimens have been shown to provide continued antianginal protection. It is clear that the objective of providing 24-h antianginal protection with the organic nitrates cannot be achieved. With appropriate dosing schedules, however, it is possible to improve exercise tolerance throughout the major portion of the 24-h dosing period.

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)

Sustained effect of and lack of development of tolerance to controlled-release isosorbide-5-mononitrate in chronic stable angina pectoris

Tolerance has been shown to develop when nitrate preparations are used in such a manner as to produce plasma levels within the therapeutic range continuously over a 24-hour period. However, a period of reduced or low nitrate plasma levels of a few hours per day may limit or completely prevent tolerance development. In 18 patients with chronic stable angina pectoris, a single 60-mg daily dose of a controlled-release preparation of isosorbide-5-mononitrate (ISMN) was compared with the administration of 30 mg, 4 times daily, of immediate-release isosorbide dinitrate (ISDN) in a double-blind, randomized, placebo-controlled, crossover study. The comparisons were carried out on the first day of therapy and after 11 to 14 days of continuous therapy to assess the duration of effectiveness and the development of tolerance. On short-term therapy, both drugs produced a significant improvement in treadmill walking times to moderate angina in comparison with placebo. The values for ISMN were 87 +/- 99 seconds (23%) at 12:30 P.M., 72 +/- 91 seconds (19%) at 5 P.M. and 51 +/- 81 seconds (13%) at 8:30 P.M. For ISDN, the respective values were 71 +/- 83 seconds (19%), 89 +/- 98 seconds (24%) and 79 +/- 87 seconds (21%). There were no significant differences between drugs. Plasma nitrate levels for each drug paralleled the improvements in exercise performance.(ABSTRACT TRUNCATED AT 250 WORDS)