Nitroglycerin ointment effective for seven hours in severe angina pectoris

Towards feedback-controlled nanomedicines for smart, adaptive delivery

IMPACT STATEMENT

The timing and rate of release of pharmaceuticals from advanced drug delivery systems is an important property that has received considerable attention in the scientific literature. Broadly, these mostly fall into two classes: controlled release with a prolonged release rate or triggered release where the drug is rapidly released in response to an environmental stimulus. This review aims to highlight the potential for developing adaptive release systems that more subtlety modulate the drug release profile through continuous communication with its environment facilitated through feedback control. By reviewing the key elements of this approach in one place (fundamental principles of nanomedicine, enzymatic nanoreactors for medical therapies and feedback-controlled chemical systems) and providing additional motivating case studies in the context of chronobiology, we hope to inspire innovative development of novel "chrononanomedicines."

Transdermal nitroglycerin therapy may not prevent early postmenopausal bone loss

CONTEXT

Osteoporosis is common among postmenopausal women; animal studies and human pilot studies support the concept of nitric oxide (NO) donors reducing bone mineral density loss.

OBJECTIVE

The objective of the study was to evaluate whether NO donor, nitroglycerin, prevents postmenopausal bone loss.

DESIGN

This was a 3-yr randomized, double blinded, single-center, placebo-controlled clinical trial.

SETTING

The single-center study was conducted at the University of Medicine and Dentistry-Robert Wood Johnson Medical School (New Brunswick, NJ).

PARTICIPANTS

Participants included 186 postmenopausal women aged 40-65 yr, with lumbar bone mineral density (BMD) T-scores of 0 to -2.5.

INTERVENTION

Women, stratified by lumbar T-score (<-1.50 and >or=-1.50) and years since menopause (5 yr), were randomized to receive nitroglycerin ointment (22.5 mg as Nitro-Bid) or placebo ointment received daily for 3 yr. Both groups took 630 mg daily calcium plus 400 IU vitamin D supplements.

MEASUREMENTS

BMD was measured at 6 months and annually by dual-energy x-ray absorptiometry. Percent change in lumbar vertebrae BMD was the primary outcome. Hip BMD, total body bone mineral content, and height were secondary outcomes.

RESULTS

After 36 months of therapy, changes of -2.1% in the active group (n = 88) and -2.5% in the placebo group (n = 82) in lumbar spine BMD were seen (P = 0.59; 95% confidence interval -1.001, 1.975). Secondary outcomes also did not differ by intervention arm. The active group reported more headaches compared with the placebo group (57 vs. 14%, P < 0.001). Other adverse and serious adverse events were not different.

CONCLUSIONS

BMD changes did not substantially differ between postmenopausal women who received the dose of nitroglycerin tested, in comparison with a placebo. Once-daily dosing with 22.5 mg of transdermal-administered nitroglycerin was not effective (compliance adjusted dose was only approximately 16 mg/d); a sub-therapeutic dose.

Digital pulse plethysmography (DPG) in studies of the hemodynamic response to nitrates--a survey of recording methods and principles of analysis

Digital pulse plethysmography (DPG) has proved a technically simple, noninvasive, sensitive and informative technique for studying the effects of nitroglycerin and other nitrates on peripheral arteries. The importance of performing nitrate evaluation by DPG mainly in elderly subjects is emphasized. On the basis of observations with DPG some indirect conclusions on the effect of nitrates on the coronary arteries are justified. A review, with recommendations based on own experience, is given of various recording techniques and principles of evaluating quantitatively the digital volume pulse contour, with special reference to the influence of nitrates on the position and appearance of dicrotism. DPG seems to be a convenient, noninvasive and helpful procedure in studies on the development of nitrate tolerance.

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.

The effect of nitroglycerin ointment on exercise-induced angina: a multicenter trial

The efficacy of nitroglycerin ointment was determined by treadmill exercise testing through a randomized, double-blind crossover trial with placebo in 22 patients with chronic stable exertional angina. On different days, 3 cm of nitroglycerin ointment (NGO, 18 mg) and placebo ointment were applied over the epigastric region, followed by the exercise test 1 hour later. The maximal exercise time was 459 +/- 124 seconds after application of placebo and 510 +/- 113 seconds after application of NGO, and the exercise time to 1 mm of ST-segment depression was significantly extended to 297 +/- 110 seconds after placebo and 366 +/- 134 seconds after NGO (p less than 0.01, p less than 0.001, respectively). ST-segment depression at the endpoint of exercise was significantly reduced from 2.4 +/- 1.2 mm to 1.5 +/- 0.7 mm after application of NGO (p less than 0.01). There was no difference in rate-pressure product at the endpoint of exercise between placebo and NGO. Adverse reactions were elicited in 5 of 22 patients. The results of this present study suggest that NGO is effective in the treatment of exertional angina.

Nitrate tolerance in angina pectoris

Tolerance to the hemodynamic and antianginal effects of the organic nitrates develops rapidly during therapy. This has been documented with a variety of nitrate preparations and with different routes of administration. Dosing strategies designed to provide therapeutic plasma nitrate concentrations throughout the 24 hours of the day are regularly associated with the development of tolerance. Recent information indicates that dosing schedules providing a nitrate-free period will permit continued efficacy of the organic nitrates without tolerance development. This can be accomplished in several ways. With oral preparations of isosorbide dinitrate, medication can be given 3 times daily, omitting the evening dose. Buccal nitroglycerin is usually given 3 times daily after meals, and this has been shown not to be associated with tolerance. Likewise, preliminary studies suggest that removal of the nitroglycerin patches for a period of several hours each day will prevent the development of tolerance. Much needs to be learned about the nitrate-free period. With oral isosorbide dinitrate, it appears that 12 hours is required, but this could be substantially less with nitroglycerin preparations. It is also possible that several short periods with low nitrate levels each day would suffice. Thus, simply increasing the interval between dosing of oral preparations may provide an adequate, low, nitrate-free period.

Nitrate tolerance

The organic nitrates are the most widely used agents in the management of patients with angina pectoris. When initially administered by the oral route, the nitrates produce profound changes in systemic hemodynamics and significant and prolonged improvement in exercise duration. It has been shown that during short periods of regular oral nitrate administration, the hemodynamic, antiischemic and antianginal effects of the nitrates are greatly reduced. Thus, when initially administered, oral isosorbide dinitrate prolongs exercise duration for a period of several hours, but during sustained 4-times-daily therapy, exercise tolerance is improved for only 2 hours after administration. Studies with transdermal preparations of isosorbide dinitrate and nitroglycerin also show improvement during short-term administration for up to 8 hours, but after several days of once-daily therapy, the effects of these agents are similar to placebo. It is apparent that nitrate tolerance is a clinically relevant problem. Although tolerance develops rapidly during nitrate therapy, it is reversed promptly during nitrate-free periods. Oral nitrates maintain their antianginal effects when given 2 or 3 times daily with provision of a nitrate-free period. Studies are currently underway to investigate the effects of intermittent administration schedules with transdermal nitrate preparations.

Plasma levels of nitroglycerin generated by three nitroglycerin patch preparations, Nitradisc, Transiderm-Nitro and Nitro-Dur and one ointment formulation, Nitrobid

Twenty-four healthy male subjects participated in a study comparing plasma concentrations of nitroglycerin generated by single applications of Nitradisc 32 mg, Transiderm-Nitro 50 mg and Nitro-Dur 104 mg patches and from one inch of Nitrobid 2% ointment. The three patch preparations are designed to release 10 mg nitroglycerin systemically over a 24 h period. Nitrobid ointment is intended to deliver 15 mg nitroglycerin per inch of ointment, and to be reapplied at least every 8 h. Blood was taken for nitroglycerin assay up to and including 24 h after each application. Assay for nitroglycerin was performed using a gas chromatography-mass spectrometry technique. Plasma concentrations of nitroglycerin were sustained up to the 24 h mark with all three patch preparations, but not with application of Nitrobid ointment. Nitrobid was associated with a rapid rise in nitroglycerin plasma concentrations maximal 1 h after application. Plasma concentrations of nitroglycerin absorbed from Nitrobid ointment fell below those absorbed from all three patch preparations after 8 h. Clinically, all four formulations were similar with respect to side effects, with headache and dizziness being the most common.

Nitrate tolerance

Nitrate tolerance may be defined as that condition in which increasing nitrate doses are required to induce a given hemodynamic or antianginal effect. Tolerance may be due to changes in pharmacokinetics or to alterations in the property of target tissues, making them less sensitive to the nitrate effect. The question of nitrate tolerance has been addressed using 4-times-a-day therapy with oral isosorbide dinitrate, daily therapy with long-acting isosorbide dinitrate ointment and once-a-day therapy with nitroglycerin patches. Each of these treatment modalities is associated with initial beneficial effects, but during sustained therapy, there is marked attenuation of the effect both in magnitude and duration. Thus the concept that stable nitroglycerin blood levels over 24 hours are desirable appears to be incorrect. Preliminary hemodynamic studies suggest that short periods of nitrate withdrawal restore the hemodynamic effect of the nitrates, and it is postulated that intermittent nitrate therapy may be desirable in the management of angina. Transmucosal nitroglycerin administration for a 15-hour period with a 9-hour washout period was recently undertaken. The results demonstrated that this method of nitrate administration is not associated with development of tolerance to its antianginal effects. Large doses of transdermal nitroglycerin, varying from 45 to 100 mg during short-term studies, have been shown to result in only minimal increases in exercise tolerance at 24 hours. These findings, plus evidence that with smaller doses tolerance occurs after only 1 week of once-a-day therapy, challenge the concept that larger nitroglycerin dosages, administered once a day by transdermal patches, could be effective throughout a 24-hour period in patients with angina pectoris.(ABSTRACT TRUNCATED AT 250 WORDS)