First data on effects and pharmacokinetics of isosorbide-5-mononitrate in normal man

Formulation and evaluation of polyelectrolyte complex-based matrix tablet of Isosorbide Mononitrate

Introduction:

The polyelectrolyte Complexes (PECs) are based on ionic cross-linking. They have been employed to prepare a sustained release matrix tablets. These systems are based upon the fact that their structure can entrap the drug within them. Isosorbide Mononitrate (ISMN) is an anti-anginal organic nitrate vasodilator used in the treatment of various cardiovascular disorders and prophylaxis of angina Pectoris, which is poorly absorbed from the upper GIT, hence CR formulation is desirable.

Materials and Methods:

Chitosan (CH)/Sodium alginate (SA), Guar gum (GG), and Xanthan gum (XG) were used as PECs, and were prepared using different proportions i.e., in 1:1 and 1:2 ratio. The optimum ratio of CH: SA, CH: GG and CH: XG was in the ratio was 1:2; these are formed due to electrostatic interaction between oppositely charged poly ions. These normally employ a hydrophilic matrix system. Matrix tablet of ISMN was formulated by using PECs as matrix forming agent by wet granulation technique.

Results:

The tablets were evaluated for hardness, wt variation, drug content, and in-vitro dissolution studies and found to be within limits. Release kinetics data indicated that ISMN released from the PECs-based matrix tablets of CH-SA, CH-GG and CH-XG CP in 1:1 and 1:2 ratio, followed Fickian and non-Fickian diffusion mechanism respectively. Thus, the drug release rate was extended for over a period of more than 12 h stability studies. There is no significant difference in the mean % drug released from formulation CH-X₂ after storing for 3 months at 40°C/75% RH. The FT-IR spectra revealed that there was no interaction between polymers and drug, Statistical analysis showed a significant differences (P < 0.05) for the amount of ISMN released from the formulations (MXG) and formulations (CH-X₂).

Conclusion:

Formulation CH-XG₂ (1:2) showed better sustained release of highly water-soluble ISMN with the desired release rate. Thus, the formulated PECs-based matrix tablets seems to be a potential candidate for sustained drug delivery of highly soluble drug ISMN in the symptomatic therapy of angina pectoris.

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

Background

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

Methods and design

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

Discussion

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

Trial registration

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

A novel multi-unit tablet for treating circadian rhythm diseases

This study aimed to develop and evaluate a novel multi-unit tablet that combined a pellet with a sustained-release coating and a tablet with a pulsatile coating for the treatment of circadian rhythm diseases. The model drug, isosorbide-5-mononitrate, was sprayed on microcrystalline cellulose (MCC)-based pellets and coated with Eudragit(®) NE30D, which served as a sustained-release layer. The coated pellets were compressed with cushion agents (a mixture of MCC PH-200/ MCC KG-802/PC-10 at a ratio of 40:40:20) at a ratio of 4:6 using a single-punch tablet machine. An isolation layer of OpadryII, swellable layer of HPMC E5, and rupturable layer of Surelease(®) were applied using a conventional pan-coating process. Central-composite design-response surface methodology was used to investigate the influence of these coatings on the square of the difference between release times over a 4 h time period. Drug release studies were carried out on formulated pellets and tablets to investigate the release behaviors, and scanning electron microscopy (SEM) was used to monitor the pellets and tablets and their cross-sectional morphology. The experimental results indicated that this system had a pulsatile dissolution profile that included a lag period of 4 h and a sustained-release time of 4 h. Compared to currently marketed preparations, this tablet may provide better treatment options for circadian rhythm diseases.

The effects of organic nitrates on osteoporosis: a systematic review

Current treatments for osteoporosis are limited by lack of effect on cortical bone, side effects, and, in some cases, cost. Organic nitrates, which act as nitric oxide donors, may be a potential alternative. This systematic review summarizes the clinical data that reports on the effects of organic nitrates and bone. Organic nitrates, which act as nitric oxide donors, are novel agents that have several advantages over the currently available treatments for osteoporosis. This systematic review summarizes the clinical data that reports on the effects of organic nitrates on bone. We searched Medline (1966 to November 2012), EMBASE (1980 to November 2012), and the Cochrane Central Register of Controlled Trials (Issue 11, 2012). Keywords included nitrates, osteoporosis, bone mineral density (BMD), and fractures. We identified 200 citations. Of these, a total of 29 were retrieved for more detailed evaluation and we excluded 19 manuscripts: 15 because they did not present original data and four because they did not provide data on the intervention or outcome of interest. As such, we included ten studies in literature review. Of these ten studies two were observational cohort studies reporting nitrate use was associated with increased BMD; two were case control studies reporting that use of nitrates were associated with lower risk of hip fracture; two were randomized controlled trials (RCT) comparing alendronate to organic nitrates for treatment of postmenopausal women and demonstrating that both agents increased lumbar spine BMD. The two largest RCT with the longest follow-up, both of which compared effects of organic nitrates to placebo on BMD in women without osteoporosis, reported conflicting results. Headaches were the most common adverse event among women taking nitrates. No studies have reported on fracture efficacy. Further research is needed before recommending organic nitrates for the treatment of postmenopausal osteoporosis.

Organic nitrates for osteoporosis: an update

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

Nitric oxide donors for the treatment of osteoporosis

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

Headache-type adverse effects of NO donors: vasodilation and beyond

Although nitrate therapy, used in the treatment of cardiovascular disorders, is frequently associated with side-effects, mainly headaches, the summaries of product characteristics of nitrate-containing medicines do not report detailed description of headaches and even do not highlight the possibility of nitrate-induced migraine. Two different types of nitrate-induced headaches have been described: (i) immediate headaches that develop within the first hour of the application, are mild or medium severity without characteristic symptoms for migraine, and ease spontaneously; and (ii) delayed, moderate or severe migraine-type headaches (occurring mainly in subjects with personal or family history of migraine), that develop 3-6 h after the intake of nitrates, with debilitating, long-lasting symptoms including nausea, vomiting, photo- and/or phono-phobia. These two types of headaches are remarkably different, not only in their timing and symptoms, but also in the persons who are at risk. Recent studies provide evidence that the two headache types are caused by different mechanisms: immediate headaches are connected to vasodilation caused by nitric oxide (NO) release, while migraines are triggered by other actions such as the release of calcitonin gene-related peptide or glutamate, or changes in ion channel function mediated by cyclic guanosine monophosphate or S-nitrosylation. Migraines usually need anti-attack medication, such as triptans, but these drugs are contraindicated in most medical conditions that are treated using nitrates. In conclusion, these data recommend the correction of summaries of nitrate product characteristics, and also suggest a need to develop new types of anti-migraine drugs, effective in migraine attacks, that could be used in patients with risk for angina pectoris.

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

Background

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

Methods

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

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

Discussion

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

Pharmacokinetic profile of a new controlled-release isosorbide-5-mononitrate 60 mg scored tablet (Monoket Multitab)

The influences of food, tablet splitting, and fractional dosing on the pharmacokinetics of a new controlled-release double-scored tablet containing 60 mg isosorbide-5-mononitrate (Monoket Multitab) were investigated in healthy male volunteers. Food interaction was evaluated after single dose administration under fasted conditions and after a standard high-fat breakfast. The effect of tablet splitting was assessed at steady-state, after 5 days of once daily dosing with the tablet taken intact or trisected. The influence of fractional dosing was assessed after 1 and 6 days of daily regimen of 40 mg in the morning (2/3 of a tablet) and 20 mg in the evening (1/3 of a tablet). The pharmacokinetics of isosorbide-5-mononitrate after taking the tablet intact or in three fragments were very similar with a mere 10% increase of maximum plasma concentration (C(max)) for the latter, while the time to peak (T(max)) decreased from 5 to 4 h and areas under the concentration vs. time curves (AUCs) were virtually unchanged. Morning trough concentration reached 53 and 46 ng/ml, respectively. Administration of the intact tablet after a high-fat breakfast increased C(max) by 18% and AUC by 21%, and slightly delayed T(max) from 5 to 6h. During fractional dosing, morning and evening C(max) reached 364 and 315 ng/ml on the first day, and 373 and 300 ng/ml on the 6th day, respectively. The ratio of AUC(0-24 h) on the last day to AUC(infinity) on the first day, was 82.1% (confidence limits 71.7-94.1%) possibly resulting from peripheral volume expansion. The release characteristics of Monoket Multitab are thus moderately influenced by concomitant intake of food and to a very minor extent by tablet breaking. Fractional dosing allows to achieve lower peak and higher morning trough levels, while total exposure is comparable to that during once daily dosing (AUC(0-24 h, s.s.) of 5.55+/-1.78 and 5.71+/-1.08 microg h/ml).

Comparison of the initial hemodynamic effects of immediate-release versus sustained-release isosorbide-5-mononitrate following single oral doses

In this double-blind, randomized, placebo-controlled cross-over study, the authors investigated the initial time course of effects of isosorbide-5-mononitrate (IS-5-MN) on hemodynamic parameters in 15 healthy male volunteers after administering a single oral dose of either an immediate-release formulation (IS-5-MN 20 mg) or of a sustained-release formulation (IS-5-MN 50 mg). The latter formulation released 15 mg IS-5-MN immediately, while 35 mg of the dose was sustained release. The onset of effect on the a/b-ratio of the finger pulse curve (20 minutes after administration) and on heart rate following orthostatic challenge (30 minutes) was not different following ingestion of either the immediate-release or the sustained-release formulation. Only the systolic blood pressure following orthostatic challenge was affected earlier after ingestion of the immediate-release form of IS-5-MN (10 vs. 30 minutes). There was no statistically significant difference in the maximum effect on the measured hemodynamic parameters between the two formulations. There was no significant difference with respect to the effect per dose between both of the active treatments (i.e., IS-5-MN 20 mg immediate release and IS-5-MN 50 mg sustained release) within 6 hours after administration. The hemodynamic findings were consistent with the observed rates of the increase of plasma concentrations of IS-5-MN following both formulations. Thus, the administration of the sustained-release formulation of IS-5-MN 50 mg caused similar maximum effects when compared with an immediate-release formulation (20 mg). While the onset of effect of IS-5-MN on the a/b-ratio of the finger pulse curve and on heart rate following orthostasis was similar after administration of either the immediate- or the sustained-release formulation, the onset of effect of the sustained-release formulation on systolic blood pressure orthostasis was determined slightly later. However, the latter difference seems to be of minor clinical relevance.

Comparison of multiple-dose and once-daily nitrate therapy in 1212 patients with stable angina pectoris: effects on quality of life indices. Dutch Mononitrate Quality of Life (DUMQOL) Study Group

BACKGROUND

Nitrates, although important for the management of anginal symptoms, produce significant side effects. Little is known about their net effects on health-related, quality-of-life indices.

METHODS

In a self-controlled, 6-month study, the effects on symptoms and quality of life of multiple-dose and once-daily nitrate therapy were evaluated in 1212 patients with stable angina pectoris. Quality of life was assessed by a test battery based on the exercise-tolerance index of Wiklund, the psychological well-being index of Dupuy, and the Short Form 36 questionnaire of Stewart. The internal consistency and reliability of the multi-item scales were estimated by Cronbach's alpha coefficients.

RESULTS

The effects of the two treatment regimens on pain index and number of additional sublingual nitrate tablets required were not different. However, based on the New York Heart Association (NYHA) angina classification, patients improved better on the once-daily than on the multiple-dose regimen: by > 1 category in 281 vs 62 of the patients (P < 0.0001); mobility and psychological distress indices also improved (P = 0.006, and P = 0.007).

CONCLUSIONS

Once-daily nitrate therapy not only provides a better NYHA angina classification than multiple-dose therapy does, but also provides a better quality of life as estimated by improvement of mobility and distress indices, the most important indicators of quality of life in this category of patients.

Nitrate-induced headache in patients with stable angina pectoris: beneficial effect of starting on a low dosage. 5-ISMN headache study group

BACKGROUND

Nitrates, although important for the management of angina pectoris, cause significant headache in many patients.

METHODS

In a randomized, double-blind, crossover study, 89 patients with stable angina pectoris were studied to compare two different dosage strategies of isosorbide-5-mononitrate (5-ISMN). Patients were randomized to either 60 mg 5-ISMN once daily (od) for two weeks or to 30 mg 5-ISMN od for one week followed by 60 mg 5-ISMN od for one week. Then, there was a two-week placebo washout, after which the alternative treatment was given. The authors assessed the occurrence of angina pectoris and headache by diary cards while taking into account the number of isosorbide dinitrate sublingual puffs and paracetamole tablets required. Data were assessed for carryover and time effects.

RESULTS

The two dosage regimens were equally efficient for the relief of angina pectoris without development of tolerance. Thirty percent of the patients never experienced headache from the given dosages. In the remainder of them there was a highly significant time effect: the overall numbers of headache attacks in the first period of active treatment versus the second were 2,380 vs 1,400 (P < 0.003). Yet significantly fewer patients had headache on low dosage than on high dosage (45 vs 57, P < 0.02).

CONCLUSIONS

(1) Starting on a low dosage was associated with a reduced frequency and severity of headache and did not notably influence the beneficial effect on angina pectoris. (2) One in 3 patients never experienced headache from the given dosages. (3) The overall number of headache attacks in the first period of active treatment was significantly higher than in the second period irrespective of the dosages given.

Effect of isosorbide-5-mononitrate on plasma and urine levels of cyclic GMP in relation to exercise in coronary patients compared with control subjects

Nitric oxide (NO) and atrial natriuretic peptide (ANP) relax vascular smooth muscle increasing levels of cyclic guanosine 3':5' monophosphate (cGMP). Nitrovasodilators act as exogenous nitric oxide donors. The aim of this study was to ascertain the response of cGMP to exercise without medication and after the administration of 20 mg of isosorbide-5-mononitrate (IS-5-MN) in coronary patients (n = 8) and healthy control subjects (n = 9). A third group of 10 normal volunteers was studied to test plasma cGMP response to second exercise test without IS-5-MN administration. Plasma cGMP increased significantly in both patients (P < 0.02) and controls (P < 0.01) after the first ergometry. After IS-5-MN administration, plasma cGMP did not increase either before or after exercise. In normal volunteers without IS-5-MN plasma cGMP increased significantly after first (P < 0.004) and second (P < 0.0008) exercise test. In conclusion, plasma cGMP increases during exercise. Administration of IS-5-MN does not raise plasma cGMP and neither does performance of further exercise after its administration.

Eccentric dosing with isosorbide-5-mononitrate in angina pectoris

In a placebo-controlled, parallel, double-blind study, 214 patients with stable angina were studied. Doses of 5, 10 and 20 mg of immediate-release isosorbide-5-mononitrate (IS-5-MN) or placebo were administered at 0800 and 1500 hours for a period of 3 weeks. On days 1 and 14, patients underwent exercise testing before, and 2 and 7 hours after both doses; on days 7 and 21, testing was performed 2 hours after morning dosing. Study variables included total exercise duration and time to moderate angina. On day 1, the active treatment groups showed improvement over the placebo group 2 and 7 hours after dose 1, and 2 hours after dose 2. Throughout the subsequent study period, each active treatment group was superior to placebo 2 hours after the first and second doses. Only the 20 mg dose increased exercise duration 7 hours after dosing, and this was observed after both doses 1 and 2 on day 14. There were fewer episodes of angina in patients receiving the 20 mg dose. There was no increase in nocturnal angina during eccentric dosing with IS-5-MN. In comparing exercise times throughout the study, tolerance did not develop during eccentric dosing. The morning exercise tests before tablet administration showed a progressive increase during the study period, with slightly greater improvement in patients receiving active therapy. This absence of a zero hour effect suggests that rebound does not occur during eccentric dosing with immediate-release IS-5-MN.

Evaluation of bioavailability and pharmacokinetics of two isosorbide-5-mononitrate preparations in healthy volunteers

The objective of this study was to determine both the pharmacokinetic parameters and the bioavailability of two commercial 20-mg isosorbide-5-mononitrate (IS-5-MN) preparations (test and reference preparation) after single oral administration. For this purpose, the test and the reference preparation were examined in 24 healthy male volunteers according to a randomized 2-way cross-over design, blood samples were withdrawn up to 24 hours postadministration, and plasma concentrations of IS-5-MN were quantified by a gas chromatography (GC) method. Both preparations led to peak plasma levels of approximately 360 ng/mL IS-5-MN in the mean 0.76 hour (test) and 0.94 hour (reference preparation) after application; the plasma half-lives were about 5.2 hours, and for the areas under the curve (AUC(0-infinity)), mean values of 2741 (test preparation) and 2742 hour.ng/mL (reference preparation) were found. The statistical comparison (analysis of variance, confidence intervals) of the pharmacokinetic parameters found in the study resulted in bioequivalence of both IS-5-MN preparations. The undesired side effects/concomitant symptoms observed are known to occur after IS-5-MN administration.

Dose-dependent headache response and dilatation of limb and extracranial arteries after three doses of 5-isosorbide-mononitrate

The aim of the present study was to compare the ability of different doses of isosorbide-5-mononitrate (5-ISMN) to cause dilatation of medium sized and small arteries, and to examine the intensity and duration of any headache produced. Ten healthy volunteers each received 3 doses of 5-ISMN and placebo on separate days. The diameters of the radial and superficial temporal arteries were repeatedly measured with high frequency ultrasound and pain was scored using a 10 point verbal scale. A clear dose-relationship was found for plasma concentrations and headache, and for changes in the diameter of the temporal artery, but not for the radial artery. It is concluded that headache after 5-ISMN is caused by arterial dilatation or by mechanisms responsible for the arterial dilatation. Ultrasound monitoring of arterial diameters is an important and sensitive tool in the evaluation of nitrates and other vasodilators.

A combined single and multiple dose pharmacokinetic study of oral isosorbide-5-mononitrate in healthy volunteers

Pharmacokinetics of 20 mg isosorbide-5-mononitrate (IS-5-MN) after single and multiple administration of two different tablet formulations were investigated in twelve healthy human subjects using an open, randomized, two-way crossover experimental design. Pentacard 20 mg tablets were compared with Ismo 20 mg tablets. After single-dose administration, both preparations caused a rapid increase in IS-5-MN plasma levels with the peak plasma concentration occurring between 0.5 and 1.5 h. For both formulations, the mean plasma half-life was found to be approximately 5 h after a single dose. In steady state during multiple dosing (t.i.d. at 8 h dosing intervals), a reduced elimination rate was observed. In line with this observation, the area under the plasma concentration-time curve (AUC) for one 8 h dosing interval during multiple dosing was higher than the extrapolated AUC after a single dose. Based on statistical evaluation of the various relevant pharmacokinetic parameters calculated from the plasma concentrations occurring after single and multiple dosing, the tablet formulations are judged to be bioequivalent.

Efficacy of nifedipine and isosorbide mononitrate in combination with atenolol in stable angina

Many patients with angina pectoris whose symptoms are not completely controlled by beta-blockers are treated with several types of drugs, but it is not clear whether addition of a calcium-channel antagonist and/or a nitrate confers any advantage over beta-blockade alone. 18 patients receiving atenolol for stable angina pectoris completed a double-blind, randomised, crossover trial of atenolol treatment plus placebo, isosorbide mononitrate, nifedipine, and mononitrate and nifedipine (triple therapy). The patients were assessed subjectively and by treadmill exercise testing and 24 h ambulatory electrocardiographic recordings at the end of each 4-week treatment period. There were no significant differences among the treatment periods in angina attack rates, glyceryl trinitrate consumption, exercise duration to onset of angina or 1 mm ST depression, or duration of symptomless ischaemia. Total exercise duration was longer on atenolol plus mononitrate than on atenolol alone (mean difference 46 [95% confidence interval 18-88] s; p = 0.005), atenolol plus nifedipine (36 [2-71] s; p = 0.04), or triple therapy (28 [6-61] s; not significant). In 12 patients the exercise time was shorter on triple therapy than on atenolol plus mononitrate alone. Although "maximum" antianginal treatment with two or three drugs is commonly accepted, this approach confers no substantial advantage over optimum beta-blockade as monotherapy. If a second drug is needed, there is a slight advantage in favour of isosorbide mononitrate, but if this is not effective, treatment should be changed rather than added. Many patients with angina pectoris seem to be pharmacologically overtreated.

Pharmacokinetics of oral isosorbide-5-mononitrate in patients with ischemic heart failure

This study compared the pharmacokinetics of orally administered isosorbide-5-mononitrate (20 mg) in patients with and without signs of ischemic heart failure after acute myocardial infarction. The central venous pressure was used as a parameter of global myocardial function and to separate 17 patients into two groups with normal (group I: CVP less than 6 cmH2O; Killip class I; n = 9) and elevated (group II: CVP greater than or equal to 6 cmH2O; Killip class II-III; n = 8) pressure. As compared to subjects with normal CVP patients with hemodynamic impairment showed a markedly lower peak concentration of isosorbide-5-mononitrate levels (475 +/- 32 vs 663 +/- 38 ngml-1; p less than 0.01; mean +/- SEM) which occurred delayed (32 +/- 6 vs 55 +/- 9 s; p less than 0.05). Reduced cardiac function also resulted in a prolonged elimination of isosorbide-5-mononitrate as was suggested by the diminished elimination rate constant (0.14 +/- 0.01 vs 0.18 +/- 0.01 h-1; p less than 0.05). Thus, in patients with ischemic heart failure cardiac performance influences both the absorption and apparent elimination phase of oral isosorbide-5-mononitrate.

A multicentre open comparison of isosorbide-5-mononitrate and nifedipine given prophylactically to general practice patients with chronic stable angina pectoris

A total of 126 patients from general practice with chronic stable angina pectoris entered the treatment phase of this open, randomized, crossover comparison of 20 mg isosorbide-5-mononitrate, and 20 mg nifedipine. Both treatments were given orally, three times daily, for 4 weeks and sublingual administration of glyceryl trinitrate was allowed throughout. Over the whole treatment period, there was no statistically significant difference between treatments for anginal attacks. However, significantly fewer glyceryl trinitrate tablets were required by patients receiving prophylaxis with nifedipine, although this difference was too small to be of clinical significance. No statistical difference existed between treatments in respect of scores for 'overall intensity of pain', 'physical exercise ability' and 'general well-being'. Of those patients who expressed a preference, the majority preferred the second treatment with no statistically significant difference between isosorbide-5-mononitrate and nifedipine. Both treatments showed similar levels of adverse events, the major difference (not significant) being for flushing of the skin which occurred in five patients given nifedipine compared with one patient given isosorbide-5-mononitrate. It is concluded that, in clinical terms, the two treatments were similar. Headache and dizziness/giddiness were the most frequently recorded adverse events.

Lack of effect of asymmetrical dosage timing of isosorbide-5-mononitrate on nitrate tolerance during long-term administration

Isosorbide 5-mononitrate is an active metabolite of isosorbide dinitrate and possesses many theoretical advantages over its parent drug. However, the development of partial tolerance has been demonstrated when the drug is given 12 hourly or 8 hourly. We have therefore evaluated the acute and sustained (2 weeks) effects of isosorbide-5-mononitrate 40 mg given twice daily (08.00 h and 14.00 h, allowing an 18-h dose-free period) in 19 patients with stable chronic angina, using computerized exercise testing and a placebo-controlled, double-blind, randomized trial protocol. There were two phases of 2 weeks each in which patients received placebo or active isosorbide-5-mononitrate. Acute testing was performed 2 h after the first dose and chronic testing 2 h after the morning dose on Day 14. Acute testing showed an increase in exercise time from a mean (SD) of 6.7 (2.2) min to 10.1 (2.95) min (P less than 0.01) after a single dose of isosorbide-5-mononitrate 40 mg. The time to 1 mm of ST depression, and rest and peak exercise heart rates increased significantly during acute testing with isosorbide-5-mononitrate; resting and peak exercise systolic blood pressures fell significantly. Due to drop outs cross-over analysis was performed on 11 patients who completed both chronic phases and 13 patients were assessed for the comparison of acute isosorbide-5-mononitrate with chronic isosorbide-5-mononitrate. After 2 weeks of therapy exercise time did not show a sustained increase 8.01 (2.14) min chronic placebo to 8.58 (1.93) min chronic isosorbide-5-mononitrate.(ABSTRACT TRUNCATED AT 250 WORDS)

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

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

Acute effect of various doses of isosorbide-5-mononitrate on hemodynamic and exercise performance in coronary artery disease

The optimal dose of nitrates is still controversial, as chronic usage of too high a dose may result in a decrease in vascular response. The dose should be determined to reduce preload acutely, and not to decrease the activity during chronic therapy. To determine this dose, 50 patients with angiographically confirmed coronary artery disease were studied. The effects on heart rate and mean systemic and pulmonary arterial pressures at rest and during exercise, and work capacity and duration were measured. The patients were classified into 5 groups, receiving placebo or isosorbide-5-mononitrate, 5, 10, 20 and 50 mg, respectively, as a single oral dose. Placebo had no effect on the measured parameters. All doses of isosorbide-5-mononitrate reduced mean pulmonary arterial pressure: 10 mg--by 16% at rest and 24% during exercise; 20 mg--24% and 34%, respectively (a near maximal effect); and 50 mg--27% and 38%. Similar results were found also for work capacity: 10 mg increased work capacity by 33%; 20 mg--79%; and 50 mg--56%. Thus, the therapeutically optimal single dose is about 20 mg. Higher doses produce no additional benefit and increase the risk for tolerance development.

The effect of food on the absorption of slow-release isosorbide-5-mononitrate tablets

The influence of food on the absorption characteristics of slow release isosorbide-5-mononitrate tablets was investigated in 10 normal healthy volunteers. There were no differences in the peak concentration achieved or the area under the curve, but the peak concentration occurred later when the drug was administered after food. The apparent elimination half-life ranged from 4.7 to 10.1 h. Bioavailability of slow-release isosorbide-5-mononitrate is therefore unaffected by food, but there is a slower rate of absorption.

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.

Hemodynamic effects of oral isosorbide-5-mononitrate and dinitrate in ischemic heart failure

Isosorbide-5-mononitrate (ISMN), the main metabolite of isosorbide dinitrate (ISDN) was recently introduced in clinical use. The hemodynamic effects of oral ISMN and ISDN, administered in equal doses, were studied in a randomized, crossover fashion in 20 patients with pump failure of ischemic etiology. Baseline hemodynamic criteria for admission into the study were: pulmonary capillary wedge pressure (PCW) of at least 20 mmHg and systolic arterial pressure (AP) above 90 mmHg. Hemodynamic parameters were serially measured and systemic vascular resistance was calculated up to 6 h postadministration of either ISMN or ISDN single dose (40 mg). Maximal effects obtained were statistically significantly different from baseline. While ISMN and ISDN appeared to be equipotent in reducing the filling pressure, with a maximum effect reached in 60-120 min, the mononitrate maintained its effects for a longer period.

Medical treatment of patients with severe exertional and rest angina: double blind comparison of beta blocker, calcium antagonist, and nitrate

The role of medical treatment of patients who had resting nocturnal angina as well as exertional angina was investigate. The effects of atenolol 100 mg a day, nifedipine 20 mg three times a day, and isosorbide mononitrate 40 mg twice a day were investigated in a double blind, triple dummy randomised study. Nine patients with coronary artery disease, early positive exercise tests, and transient daytime and nocturnal ambulatory ST segment changes were initially assessed off all antianginal medication. They were then treated with each drug for three five day periods. Angina diaries were reviewed and maximal treadmill exercise tests and 48 hour ambulatory ST segment monitoring were performed at the end of each treatment period. Resting and exercise heart rate and blood pressure were significantly lower on atenolol than on either isosorbide mononitrate or nifedipine. The duration of exercise to 1 mm ST segment depression was significantly greater on atenolol than on isosorbide mononitrate. Only one patient had an improvement in exercise tolerance on nifedipine that was greater than the improvement on atenolol; this patient had single vessel disease. The total number and duration of episodes of ST segment change during ambulatory monitoring were significantly lower with atenolol than on either isosorbide mononitrate or nifedipine. Nocturnal ST segment changes were abolished in six patients on atenolol, in six patients on nifedipine, and in five patients on isosorbide mononitrate. When nocturnal ST segment changes occurred, their frequency was reduced with all three drugs. Pain was abolished in four patients on atenolol and pain relief was significantly better on atenolol than on isosorbide mononitrate. There was no significant difference in pain relief between isosorbide mononitrate and nifedipine. Thus beta receptor blockade with atenolol was the most effective means of reducing myocardial ischaemia both during exercise and at rest at night without causing deterioration in any patient. Nocturnal myocardial ischaemia in patients with severe coronary artery disease can be effectively treated with beta receptor antagonists and vasodilators.

Duration of effects and tolerance of slow-release isosorbide-5-mononitrate for angina pectoris

Isosorbide-5-mononitrate (IS-5MN) is an active metabolite of isosorbide dinitrate, but unlike its parent compound, is nearly 100% bioavailable after oral administration. Once-a-day therapy with a slow-release formulation of IS-5MN is used widely in Europe for 24-hour prophylaxis of angina pectoris. In a randomized, crossover, double-blind, placebo-controlled study, the duration of effects of 50 and 100 mg of slow-release IS-5MN were evaluated after the first dose and after once-a-day therapy for 1 week in 9 patients with stable angina pectoris. Compared with placebo values, standing blood pressure decreased (p less than 0.001) and exercise time to the onset of angina and total exercise duration increased (p less than 0.008 and p less than 0.003) at 4 hours, but not at 20 or 24 hours after first dose of 50 and 100 mg of slow-release IS-5MN. After once-a-day therapy for 1 week, no improvement in exercise duration or reduction in ST-segment depression was seen after 50 or 100 mg of slow-release IS-5MN at 4, 20 or 24 hours despite high plasma IS-5MN concentrations. Thus, despite therapeutic plasma concentrations, 50 and 100 mg of slow-release IS-5MN did not exert antianginal or anti-ischemic effects at 20 and 24 hours after the first dose and at 4, 20 and 24 hours after sustained once-a-day therapy for 1 week.

Pharmacokinetics of isosorbide-5-nitrate during haemodialysis and peritoneal dialysis

The pharmacokinetics of isosorbide-5-nitrate (IS-5-N) was studied in ten patients on haemodialysis (HD) after a single oral dose of 20 mg IS-5-N, and in six patients on continuous ambulatory peritoneal dialysis (CAPD) after repeated oral doses of 3 X 20 mg IS-5-N. There was significant removal of IS-5-N from blood during HD; Cmax decreased by about 20%, AUC(0-8 h) by 30% and t1/2 by about 20% from 4.3 to 3.4 h, and plasma clearance was increased by 81 ml/min. No important loss of IS-5-N was observed in patients on CAPD.

Isosorbide-5-mononitrate and isosorbide dinitrate retard in the treatment of coronary heart disease: a multi-centre study

A multi-centre study was carried out in 200 coronary patients to compare the efficacy and tolerance of isosorbide dinitrate retard (40 mg) and isosorbide-5-mononitrate (20 mg) with regard to the frequency of anginal attacks and consumption of sub-lingual (short acting) nitrates. After receiving treatment for 2 weeks with isosorbide dinitrate retard at a dosage of 2 or 3 tablets per day, only those patients continued the study who had a weekly average of 4 or more anginal attacks during this basal period. The selected patients were divided in 4 groups of 50 patients and received treatment for a further 4 weeks with either isosorbide dinitrate retard at a dosage of 2 tablets (Group D2) or 3 tablets (D3) per day or isosorbide-5-mononitrate at a dosage of 2 tablets (Group M2) or 3 tablets (Group M3) per day. A progressive improvement in symptoms was seen at the end of 2 and 4 weeks with both drugs. The greater therapeutic benefits were obtained in patients in Group M2; the greater difference was observed between Group M2 and D2 (p less than 0.01) and there were also significant differences (p less than 0.05) between Groups M2 and D3 and between Groups M3 and D3. Analysis of the results showed that the more frequently angina attacks had occurred during the basal period, the greater was therapeutic benefit obtained with isosorbide-5-mononitrate compared to isosorbide dinitrate retard at the end of the study. Heart rate at the end of the study showed a slight tendency to increase over initial levels in all groups. In contrast, systolic blood pressure decreased very significantly in all groups (p less than 0.001). Diastolic blood pressure also decreased in all groups but only to a highly significant degree in patients treated with isosorbide-5-mononitrate (p less than 0.001) and the two sub-groups M2 and M3 (p less than 0.005). In patients treated with isosorbide dinitrate retard, the reduction in diastolic pressure was only statistically significant when the 100 patients in the group were considered as a whole (p less than 0.05), while this was not the case for the two sub-groups D2 and D3. The most frequent side-effect was headache, which improved gradually. During treatment there was a progressive dissociation between reduction in the intensity and frequency of this adverse effect and the increasing anti-anginal action of the nitrates.

Acute and sustained effects of isosorbide 5-mononitrate in stable angina pectoris

Isosorbide 5-mononitrate (IS 5-MN) is an active metabolite of isosorbide dinitrate and is widely used as an antianginal agent. The acute and subacute (2 weeks) effects of IS 5-MN, 40 mg twice daily, were evaluated in 18 patients with stable angina pectoris using computerized exercise testing and a placebo-controlled, double-blind, randomized trial protocol. There were 2 phases of 2 weeks each in which patients received placebo or active IS 5-MN. Acute testing (8 patients) was performed 2 hours after the first dose and subacute testing 2 hours after the morning dose on day 14. Acute testing showed an increase in exercise time from a mean (+/- standard error of mean) of 8.2 +/- 0.6 minutes to 11.1 +/- 0.5 minutes (p less than 0.001) after a single dose of IS 5-MN. Time to 1 mm of ST depression increased significantly and peak exercise ST-segment depression decreased significantly. Rest and peak exercise heart rate increased significantly during acute testing with IS 5-MN; blood pressure did not change significantly. After 2 weeks of therapy, exercise time had not changed (9.9 +/- 0.6 with placebo to 9.7 +/- 0.6 minutes). The beneficial effects on ST-segment variables were sustained at 2 weeks. The data suggest that there is an attenuation of effect with respect to exercise time and sustained beneficial effect on the ST-segment variables. This may be a result of development of partial tolerance to IS 5-MN after 2 weeks of therapy.

The bioavailability of oral nitroglycerin

In the 1970's, the efficacy of oral nitroglycerin therapy was seriously challenged, primarily on the basis of animal studies showing complete first-pass hepatic metabolism of nitroglycerin. Today, it is generally accepted that high oral doses of nitroglycerin do show antianginal efficacy. It has been suggested that this efficacy results from saturation of hepatic metabolism by the large oral doses administered, although the experimental evidence in humans purporting to support this may be questioned. In the present investigation, the bioavailability of oral nitroglycerin when administered in a capsule dosage form and as a solution was determined. Oral doses of nitroglycerin were less than 1% bioavailable. However, substantially high concentrations of the relatively low activity dinitrate metabolites were measured in plasma. We hypothesize that the activity of oral nitroglycerin preparations may result from high concentrations of the dinitrate metabolites, although this was not directly tested in the bioavailability studies described here.

Pharmacokinetics of isosorbide dinitrate and its mononitrate metabolites after intravenous infusion

Plasma concentrations of isosorbide dinitrate (ISDN) and its two active metabolites 2-isosorbide mononitrate (2-ISMN) and 5-isosorbide mononitrate (5-ISMN) have been measured during and for 6 hr after intravenous infusion at a rate of 2.5 mg/hr during 1.75 hr in six cardiac patients, by a capillary gas chromatographic method. Data were analyzed by simultaneous modeling of the observed kinetics of the three compounds. Two or three phases were detected on the postinfusion ISDN concentration-time curves. ISDN concentrations declined with a mean terminal half-life of 2.81 hr +/- 0.7 SD. The mean systemic clearance of ISDN (2.9 L/min +/- 0.7 SD) and its mean total volume of distribution (259 L +/- 48 SD) were relatively high. Plasma 5-ISMN concentrations were 5- to 6-fold greater than those of 2-ISMN during the whole observation period. Maximum levels of 2-ISMN (6.7 ng/ml +/- 0.9 SD) and of 5-ISMN (27 ng/ml +/- 6 SD) occurred within a few minutes after the end of infusion. The mean half-lives of 2-ISMN (1.59 hr +/- 0.19 SD) and of 5-ISMN (3.78 hr +/- 0.79 SD) estimated by the model were smaller than those calculated by a model-independent method (2.95 hr +/- 0.41 SD and 5.98 hr +/- 2.22, respectively), but were in good agreement with those reported in the literature following separate administration of both metabolites to man. This study shows how such modeling can distinguish between metabolite formation and elimination processes and allow the determination of metabolite half-lives after administration of the precursor drug.

Pharmacokinetics of isosorbide-5-nitrate in renal failure

The pharmacokinetics of the antianginal drug isosorbide-5-nitrate (IS-5-N) was studied in 20 patients with varying degrees of chronic renal failure after repeated oral doses of standard 20 mg tablets t.d.s. Blood samples were taken in the steady state on the 2nd and 28th days, and the plasma level was assayed by HPLC. There was no statistically significant difference in Cssmax, t1/2 and AUCss0-8 between the 2nd and 28th days, nor was a difference found between patients with mild and severe renal failure.

Isosorbide 5-mononitrate effects on isolated rabbit aorta and vena cava: relationship between cyclic GMP and relaxation of vascular smooth muscle

The effects of isosorbide 5-mononitrate (5-ISMN) on vascular smooth muscle tone and cyclic GMP levels in isolated rabbit aorta and vena cava were compared. 5-ISMN induced concentration-dependent relaxation of noradrenaline-contracted strips of aorta and vena cava. 5-ISMN was over 100 times more potent in eliciting relaxation in vena cava than in aorta. Unlike 5-ISMN, 8-bromo cyclic GMP produced concentration-dependent relaxation with similar potency in both strips. The relaxation induced in both strips by 5-ISMN but not by 8-bromo cyclic GMP was inhibited by pretreatment with 5 X 10(-5) M methylene blue. The 5-ISMN-induced changes in tone of both strips were closely associated with those in cyclic GMP levels. 5-ISMN increased the cyclic GMP levels of both strips in a concentration-dependent manner. 5-ISMN was also considerably more potent in increasing cyclic GMP levels in vena cava than in aorta. This 5-ISMN-induced increases in cyclic GMP levels of both strips were inhibited by pretreatment with methylene blue. These results suggest that cyclic GMP could be involved in the 5-ISMN-induced relaxation of smooth muscle from both aorta and vena cava. Furthermore, the finding that 5-ISMN was more active on vena cava than on aorta both to cause relaxation and increase cyclic GMP levels indicates that cyclic GMP-mediated vasodilatation may be responsible for the pharmacological action of 5-ISMN in vivo.

Determination of isosorbide 5-mononitrate in human plasma by capillary column gas chromatography

An electron-capture gas chromatographic method for the determination of isosorbide 5-mononitrate in human plasma using a capillary column is described. Isosorbide 5-mononitrate and the internal standard (isosorbide dinitrate) are extracted from the alkalinized plasma with ether. The lower limit of detection for isosorbide 5-mononitrate is 1 ng/mL of plasma.

Pharmacokinetics of nicorandil, a new coronary vasodilator, in dogs

The kinetic disposition of nicorandil, N-[2-( nitroxy )ethyl]-3- pyridinecarboxamide (1), and its main metabolic product, N-[2-(hydroxy)-ethyl]-3- pyridinecarboxamide (II), was studied after administering intravenous and oral doses (2.5 mg/kg) of nicorandil to the same beagle dogs. The plasma concentrations were measured using a high-performance liquid chromatographic method. The pharmacokinetic data derived from intravenous administration of nicorandil were: t1/2, 0.73 plus/minus 0.11 h; Vdarea , 0.67 plus/minus 0.04 L/kg; and total plasma clearance, 13.50 plus/minus 1.05 mL/min/kg. After oral administration, nicorandil was rapidly absorbed (tmax, 0.58 plus/minus 0.11 h). The oral bioavailability was calculated as 0.72 plus/minus 0.07. The metabolic formation of the corresponding alcohol after intravenous and oral administration of the parent compound appeared to occur quite efficiently, and its elimination half-life (3.09 plus/minus 0.25 and 3.69 plus/minus 0.88 h after intravenous and oral administration of nicorandil, respectively) was longer than that of the parent compound. Since the dose employed in this study was much higher than the expected therapeutic doses, whether such a good bioavailability after a lower dose of the drug would be obtained in humans remains unanswered.

Clinical pharmacokinetics of organic nitrates

Plasma concentrations of glyceryl trinitrate (nitroglycerin), isosorbide dinitrate and isosorbide 2- and 5-mononitrates in man have been measured after administration via different routes. Appropriate precautions have to be taken in the administration of these agents (to avoid loss during intravenous infusion), and in their sampling and assay. Pharmacokinetic calculations based on plasma concentrations should be viewed with caution, as the data on which these calculations are based are often very limited, and the very rapid disappearance of for example glyceryl trinitrate from plasma makes the choice of an appropriate kinetic model and exact calculations difficult. Glyceryl trinitrate disappears from plasma within a few minutes, and a high apparent volume of distribution and a very high systemic clearance are found. After oral administration, plasma concentrations are very low; with sublingual or cutaneous administration, higher plasma concentrations can be obtained, suggesting a high first-pass extraction after oral administration, but quantitative data on bioavailability are lacking. For isosorbide dinitrate the systemic clearance, although high, is lower than for glyceryl trinitrate; disappearance from the plasma is slower and plasma concentrations after different routes of administration are much higher. Here too, quantitative data on bioavailability are lacking. High plasma concentrations of isosorbide 2-mononitrate and isosorbide 5-mononitrate are found in plasma after administration of isosorbide dinitrate. These metabolites have a good bioavailability, and half-lives of around 2.5 hours for isosorbide 2-mononitrate and 5 hours for isosorbide 5-mononitrate. Only very limited data are available about the influence of disease states and interactions with food and other drugs on the kinetics of the organic nitrates. It is very difficult to correlate the effects of the nitrates to their plasma concentrations; counter-regulation, development of tolerance, and the presence of metabolites could disturb the interpretation of such a relationship. It is at present impossible to predict the pharmacological effects or the efficacy of organic nitrates on the basis of their plasma concentrations.

Pharmacokinetics of intravenous and oral isosorbide - 5 - mononitrate

The pharmacokinetics of isosorbide-5-mononitrate (IS-5-MN) has been studied in two groups of healthy volunteers after oral (n = 20) and intravenous (n = 11) administration of 20 mg, which had previously been proved to be as effective as 20 mg sustained-release isosorbide dinitrate (ISDN). IS-5-MN in serum was measured by gas chromatography using capillary columns. The kinetic calculations were carried out with a newly developed model, which assumes a virtual volume of distribution dependent on time. IS-5-MN is rapidly (invasion half-life 4.1 min) and completely absorbed from the gastro-intestinal tract without any first pass metabolism. The maximum concentration of 480 micrograms/l was reached 1.2 h after oral administration of 20 mg. The substance was distributed throughout the total body water (distribution coefficient: 0.62), and was eliminated with a terminal t1/2 of 4.1 and 4.6 h after oral and intravenous administration, respectively. Total body clearance was 115ml/min. Thus, IS-5-MN is unlike ISDN with respect to the absence of first-pass metabolism and an 8-times longer half-life. The consequences for therapy are discussed.