Hemodynamic attenuation and the nitrate-free interval: alternative dosing strategies for transdermal nitroglycerin

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.

Haemodynamic effects of glyceryl trinitrate following repeated application of a transdermal delivery system with a phasic release profile

The haemodynamic effects and plasma concentrations of glyceryl trinitrate (GTN) and its dinitrate metabolites were investigated in 8 healthy male volunteers during 5 days of application of a new transdermal delivery system (TDS) with time-dependent release characteristics, which were considered to prevent or to diminish development of nitrate tolerance. On the first and fifth day of administration the following haemodynamic parameters were determined: digital pulse ratio of height of systolic peak to height of dicrotic wave (i.e. a/b-ratio), heart rate and systolic blood pressure under orthostatic conditions. Peak plasma concentrations of GTN were 139 and 155 pg.ml-1 on the first and fifth day of treatment, and the corresponding trough concentrations (i.e. 24 h after administration) were 52.5 and 36.6 pg.ml-1, respectively. Compared to placebo, the area under the effect curve of the a/b-ratio of the digital pulse was increased on the first (25.6%) and fifth day (13%). A significant increase of heart rate and a decrease of systolic blood pressure were seen only on the first day of treatment. The haemodynamic effects of sublingual GTN 0.8 mg were reduced by 69% (a/b-ratio) and 52% (standing heart rate) on the fifth day compared to the pretreatment values. Thus, the phasic release of GTN from the new TDS can be demonstrated by the time course of the plasma concentrations of GTN and its metabolites. Nevertheless, following repeated administration the hemodynamic effects are blunted.

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)

Nitrate therapy in the elderly

Changes in the heart and blood vessels with age alter the response of the cardiovascular system to pharmacologic agents. Nitrate plasma half-life is longer and volume of distribution is larger in older persons. Apparently, these pharmacokinetic differences in older persons lead to increased venous smooth muscle responsivity to nitrates which, in turn, leads to greater reductions in central venous and pulmonary arterial pressures after nitrate administration. This is probably the explanation for the greater frequency of nitrate-induced severe hypotension and bradycardia in elderly patients with myocardial infarction compared with younger patients. Clinicians should be cognizant of the changes in the cardiovascular system which occur with age that sensitize the elderly patient to the action of organic nitrates. Initial dosages of nitrates should accordingly be less than in younger patients.

Effect of cutaneous nitroglycerin patches on coronary artery diameter: issues concerning development of tolerance

The coronary dilative and systemic responses to graded doses of intracoronary nitroglycerin were studied in 53 patients undergoing diagnostic coronary arteriography, 43 of whom had received a cutaneous nitroglycerin patch. During coronary arteriography, graded doses of 50, 100 and 200 micrograms of intracoronary nitroglycerin were given 5 min apart. An arteriogram and hemodynamic measurements were obtained after each dose. In the control group (n = 10) cumulative intracoronary nitroglycerin doses of 50, 150 and 350 micrograms caused an increase in coronary diameter in the left anterior descending artery of 20 +/- 4%, 21 +/- 3% and 22 +/- 7%, respectively, and in the circumflex artery of 18 +/- 6%, 23 +/- 8% and 18 +/- 5% (p less than 0.01 versus values in untreated group). In Group 1 (15 patients given a 5 mg/24 h nitroglycerin patch 2 to 12 h before coronary arteriography), the same intracoronary nitroglycerin doses increased the left anterior descending artery diameter by 6 +/- 2%, 7 +/- 2% and 7 +/- 2%, respectively, and the circumflex artery diameter by 3 +/- 2%, 3 +/- 2% and 1 +/- 3%. All values were statistically different from control (p less than 0.05). An even more pronounced blunting (p less than 0.01) of the coronary dilative response was observed in Group 2 (14 patients given a 15 mg/24 h nitroglycerin patch 2 to 12 h before arteriography).(ABSTRACT TRUNCATED AT 250 WORDS)

Tolerance to organic nitrates in ischemic heart disease

The development of tolerance to organic nitrates in patients with ischemic heart disease is reviewed, with particular interest in alterations to both the hemodynamic and antiischemic effects over time. The article primarily focuses on how tolerance is defined, what biochemical mechanisms are involved when this condition occurs, which agents have been associated with the development of tolerance, and what can be done to prevent or reverse the condition in patients taking nitrates for ischemic heart disease. From a historical perspective, tolerance to organic nitrates has been a recognized phenomenon since the last century. The role that blood-level determinations and nitroglycerin pharmacokinetics have in the development of tolerance is discussed, and an extensive overview of currently marketed organic nitrate preparations and a few others available only through approved investigational protocols is presented. The role of cross-tolerance is discussed as is the role that nitrate-free intervals play in partially or completely reversing the effects of tolerance during chronic nitrate therapy. Additionally, a discussion of which specific nitrate formulation are least likely to have tolerance associated with their use is included, such as short-acting nitrate formulations with the exception of the intravenous dosage form. Finally, buccal nitroglycerin is presented as another new formulation that appears to be associated with minimal tolerance in studies already completed.

Pharmacologic and pharmacokinetic comparison of antianginal agents

Calcium channel blockers, nitrates, and beta blockers are the primary agents used for the treatment of angina. Calcium has a central role in excitation-contraction, action potential generation, and ischemic cell death. The three currently available calcium antagonists are nifedipine, verapamil, and diltiazem. Second-generation agents are in development, and a classification system of calcium channel blockers is used to place the currently available agents and those on the horizon in perspective. Nitrate pharmacology and pharmacodynamics are possibly related to nitrate tolerance; however, this is a matter of some controversy. The beta blockers are all equally effective in the treatment of angina; therefore, drug selection is based on ancillary properties.

Incidence of early tolerance to hemodynamic effects of continuous infusion of nitroglycerin in patients with coronary artery disease and heart failure

Sustained therapy with nitroglycerin (NTG) has been reported to provoke the development of early tolerance. Because continuous intravenous NTG infusion is commonly used in patients with coronary artery disease and heart failure, we evaluated the incidence of early tolerance developed within the first 24 hr of therapy in 31 responders to NTG. After documentation of response to NTG, defined as a 10 mm Hg or greater or a 30% or greater reduction in mean pulmonary arterial wedge pressure (PAWP), 16 patients were blindly, randomly assigned to receive placebo and 15 patients were continued on same-dose NTG. Both groups showed an identical fall in PAWP at peak NTG titration (11 +/- 4 mm Hg). Discontinuation of NTG in the placebo group resulted in a rapid increase in PAWP to levels not significantly different from baseline (19 +/- 5 mm Hg at 2 hr vs 23 +/- 6 mm Hg at baseline; p = NS). In the NTG group, PAWP fell from 27 +/- 9 to 14 +/- 7 mm Hg, was 16 +/- 9 mm Hg at 2 hr (p less than .05 vs baseline), and continued to be significantly lower than baseline for 8 hr; however, due to attenuation of effect, PAWP values at 12, 20, and 24 hr were not significantly different from placebo or baseline values.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic effects of intermittent transdermal nitroglycerin in chronic congestive heart failure

The hemodynamic effects of intermittent and continuous treatment with transdermal nitroglycerin, 10 mg/24 hours, were compared in 10 patients with chronic congestive heart failure (CHF). Eight patients responded to initial application with more than a 20% reduction in mean pulmonary artery wedge pressure. Cardiac index increased from a control value of 2.1 +/- 0.5 to 2.4 +/- 0.6 liters/min/m2 at 2 hours (p less than 0.05) and mean pulmonary wedge pressure was reduced from 22 +/- 5 to 16 +/- 6 mm Hg (p less than 0.01). The 2 nonresponders had the largest left ventricular volumes on 2-dimensional echocardiograms. Responders were randomized to intermittent (16 hours/day) or continuous (24 hours/day) treatment for 1 month followed by a month of the alternate treatment. After 1 month of intermittent treatment, the hemodynamic response after reapplication was similar to the initial response. After another month of continuous treatment, hemodynamic values 24 hours after application were similar to initial control values and there was no change after removal and reapplication. Thus, the moderate vasodilator effect of transdermal nitroglycerin in CHF is maintained with intermittent treatment, whereas tolerance develops with continuous treatment.

Clinical experience with a transdermal nitroglycerin system

Forty-seven patients with chronic stable angina pectoris entered a thirteen-week open-label study with a transdermal therapeutic system of nitroglycerin in order to evaluate its clinical efficacy, safety, and patient acceptance. In 19 patients, a beta-blocker and in 17 patients a calcium-channel blocker were continued throughout the study period without alteration of their doses. The study consisted of a two-week run-in period and an eleven-week active drug period. Acute titration was done with nitroglycerin patches on the basis of weekly patient diaries on frequency of angina and sublingual nitroglycerin consumption. Overall, reductions in frequency of angina and in nitroglycerin consumption were statistically significant (p less than 0.05). Adverse reactions were common but tolerable. The reported side effects were headache in 32, skin rash in 18, dizziness in 10, palpitation and itching in 9 each, nausea in 7, flushing in 3, and vomiting in 1 patient. In conclusion, the present study demonstrates that individual dose titration with nitroglycerin patches for obtaining significant antianginal effect is essential. The present therapeutic system is convenient to use and well tolerated and had acceptable side effects in our study population.

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.

The haemodynamic and anti-ischaemic effects of a single tablet of 80 mg isosorbide dinitrate in slow-release formulation and a review of nitrate tolerance

There is increasing evidence that relatively constant plasma nitrate concentrations induced by 3-times-daily administration of isosorbide dinitrate can lead to an attenuation or even complete loss of the drug's anti-ischaemic effects (nitrate tolerance). We therefore assessed the dependence of nitrate tolerance development from the haemodynamic and anti-ischaemic effects of a slow-release tablet formulation of isosorbide dinitrate 80 mg, administered according to different daily dosage regimens in patients with angina. It was found that a once-daily regimen, with its consequent peak and trough plasma nitrate concentrations, is capable of protecting against exercise-induced myocardial ischaemia for about 12 hours with the circumvention of nitrate tolerance.