Simultaneous measurement of plasma isosorbide dinitrate, isosorbide-2-mononitrate, and isosorbide-5-mononitrate by gas-liquid chromatography.
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Isosorbide dinitrate and two isomeric isosorbide mononitrates are shown to be polarographically reducible in aqueous sodium perchlorate or potassium chloride solution. The current, measured at -1.6 v, versus the saturated calomel electrode is proportional to the concentration of organic nitrate in the 10-100-mug/ml range. Inorganic nitrate produces no interference. However, the mononitrate isomers produce an additive response to isosorbide dinitrate and cannot be determined individually. The polarographic method is applicable to single-tablet assay for content uniformity determination, with precision and accuracy comparable to automated colorimetric analysis. Comparison is made between replicate analyses obtained polarographically and by IR and automated colorimetric analysis for six different commercially available formulations. The polarographic determination is sensitive, specific for nitrate esters, precise, requires little sample preparation, and utilizes relatively inexpensive apparatus.
One hundred and eighty patients with acute myocardial infarction (MI) were followed up. The patients were divided into 3 groups: (1) those receiving glyceryl trinitrate (GTN) (n = 43); (2) those on isosorbide dinitrate (ISDN) (n = 66); (3) those on isosorbide-5-mononitrate (IS-5-MN) (n = 71). In all the groups, the drugs were given by long-term continuous oligovolumic infusion. Following 24 hours of administration, 66.7, 47.3, and 17.1% increases in infusion rates were required in 74.4, 72.7, and 26.8% of the patients from Groups 1, 2, and 3, respectively. All the agents produced a pronounced antianginal effect and resulted in alleviated acute left ventricular failure. The in-hospital mortality rates were 16.2, 16.7, and 12.7% in Groups 1, 2, and 3, respectively. GTN, ISDN, and IS-5-MN caused adverse effects in 4.7, 18.2, and 2.8% of the patients from Groups 1, 2, and 3, respectively.
A quadruple blind randomized cross-over study evaluated the therapeutic efficacy of twice a day long acting sustained release isosorbide dinitrate (SRISDN) in comparison with 4 times daily of the short acting isosorbide dinitrate in 18 patients with stable angina pectoris (NYHA class II-III) with a positive exercise treadmill test. The antianginal effect of sustained release isosorbide dinitrate (SRISDN) (exercise duration 472.61 +/- 112.49 sec and anginal episodes per week (1.33 +/- 1.18) was not significantly different (p less than 0.05) when compared to conventional isosorbide dinitrate (exercise duration 468.33 +/- 135.28 sec and anginal episodes per week 1.55 +/- 104). Twice a day long acting sustained release isosorbide dinitrate is as effective as four times a day conventional short acting isosorbide dinitrate. Such a regimen is likely to lead to a better patient compliance and ease of antianginal therapy.
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The vasodilatory effect of a new formula of isosorbide dinitrite (ISDN) spray on the left coronary artery was studied by comparing its effects in 46 consecutive patients who subsequently received intracoronary injection with ISDN (2.5 mg). In addition, the influence long acting and ISDN for chronic cases on the vasodilatory effects of ISDN spray and on subsequent intracoronary injection of ISDN was investigated. The patients were divided into two groups, those who had had chronic oral ISDN (Group N; 29 patients) and those who had not (Group O; 17 patients). The vasodilatory effect of ISDN spray was evaluated in segments; 5, 6, 8, 11 and 12 by AHA classification and it dilated those segments by 9.9%, 13.2%, 21.5%, 15.6% and 23.5% respectively. Subsequent intracoronary injection of ISDN dilated those segments by 10.4%, 14.0%, 27.2%, 17.9% and 29.1% respectively. The differences in the degree of vasodilation caused by ISDN spray and that caused by injection in segments 8, 11, 12 were statistically significant. However, the per cent dilation of ISDN spray in segments 5 in group N was 5.9%, and 18.4% in group O, revealing a significant difference depending on previous chronic administration of long acting ISDN. We conclude that ISDN spray did dilate the coronary artery, and subsequent intracoronary administration of ISDN dilated it further in the distal portions of the left coronary artery. Long acting oral ISDN for chronic cases seemed to attenuate the vasodilatory action of ISDN.
An effect of isosorbide dinitrate on blood pressure values in the pulmonary circulation and the right heart has been investigated in 25 patients with a history of the first transmural myocardial infarction. Group I including 12 patients has been given 5 mg isosorbide nitrate in a 60-minute intravenous infusion while group II of 13 patients has been given 10 mg of the drug in the same way. Both groups have been matched in clinical data and blood pressure value in the pulmonary circulation which has been normal. Pulmonary blood pressure has been measured with Swan-Ganz catheter prior to the administration of drug, and 15, 30, 45 and 60 minutes following an infusion. Isosorbide dinitrate in a dose of 5 mg did not decrease blood pressure in the pulmonary circulation statistically significantly. The differences in blood pressure falls did exceed 9%. Filling pressure in the right ventricle did not change either while systolic blood pressure decrease by 16.6%. A double dose of isosorbide dinitrate reduced blood pressure in the pulmonary artery by about 1/3 of the baseline value, and blood pressure in the right ventricle (mean right atrial pressure) by 57.2%. Both systolic and diastolic arterial pressures were reduced. Isosorbide dinitrate reduced blood pressure in the pulmonary circulation in patients who underwent myocardial infarction, and hypotensive effect has been dose-related. A reduction in the right ventricular filling pressure has been a one of important mechanisms decreasing pulmonary pressures.
Eighteen of infantile hydrocephalus have been treated with isosorbide dinitrate. Pharmacology of this compound is considered. It appears that completely dinitrated isosorbide is the major metabolite. Isosorbide may be effective in a variable proportion of various types of infantile hydrocephalus. Results of isosorbide dinitrate therapy in children with "communicating" and "noncommunicating" hydrocephalus are reported. Treatment was monitored by simple measurements, and it's toxicity proved to be scanty.
The coronary vasodilator properties of isosorbide dinitrate are well established but the doses generally used (1,000-2,000 micrograms) are still empirical. We studied, with the use of quantitative coronary arteriography (CAESAR System), the response of smooth vessel segments (greater than 1.85 mm diameter), preconstricted with methylergometrine (400 micrograms i.v.), to intracoronary injections of graded doses (5-100 micrograms) of isosorbide dinitrate and the effects of these injections on systemic hemodynamic parameters in 10 patients undergoing diagnostic coronary angiography. Six further patients, in whom the injections of isosorbide dinitrate were replaced by equivalent volumes of normal saline, served as controls. Relative to the diameter 5 min after injection of methylergometrine, the diameter increased by a mean +/- SD of 9 +/- 7, 26 +/- 12, 33 +/- 15, 38 +/- 14, and 39 +/- 16% after injections of 5, 15, 60, 240, and 1,000 micrograms, respectively, of isosorbide dinitrate. After a cumulative dose of 80 micrograms, subsequent doses did not cause further significant increases in diameter. Injection of saline in the control group did not alter the coronary diameter. A significant fall in systolic arterial pressure, compared to the control group, occurred at a cumulative dose of 320 micrograms. The mean arterial pressure and heart rate were unchanged. Significant coronary vasodilation occurs with intracoronary doses of isosorbide much smaller than those currently employed. Cumulative doses of 320 micrograms or more cause systemic hemodynamic changes without producing additional coronary vasodilation. During interventional cardiac procedures, where systemic hypotension is undesirable, the use of smaller doses of intracoronary isosorbide dinitrate than currently employed may be feasible and should be investigated further.
The activity of isosorbide dinitrate (ISDN) a nitrate derivative with platelet anti-aggregant properties, was studied on a model of arterial thrombosis by electric stimulation of the rat carotid arteries. In control animals, occlusive thrombosis occurred in 15.3 +/- 1.0 minutes. When administered orally in dosages of 1 to 30 mg/kg, 30 minutes before stimulation, ISDN prolonged the time to arterial occlusion by a factor of 2 to 3 times. This effect was significant from doses of 1 mg/kg. This anti-thrombotic activity was unchanged by pretreatment of 100 mg/kg I.V. of acetylsalicylic acid, a dose sufficient to inhibit prostacycline synthesis. On the other hand, its activity was completely blocked by the administration of an inhibitor of NO-synthetase, L-nitroarginine methylester (1 mg/kg I.V.). These results show that ISDN is active on a model of arterial thrombosis in the rat by a mechanism independent of prostacycline production but implying a stimulation of the formation of nitric oxide.
A previously described electron-capture GLC method for determination of isosorbide dinitrate in human plasma was adapted for the simultaneous determination of isosorbide dinitrate, isosorbide 2-mononitrate, and isosorbide 5-mononitrate using a capillary column. Quantitation was done with two internal standards. The lower limits of detection were approximately 0.5 ng/ml of plasma for isosorbide dinitrate, 2 ng/ml for isosorbide 2-mononitrate, and 20 ng/ml for isosorbide 5-mononitrate.
A GLC method for the determination of plasma isosorbide dinitrate and two metabolites, isosorbide 2-mononitrate and isosorbide 5-mononitrate, is described. The three substances are extracted from alkalinized plasma with ether. Quantitation is effected by electron-capture detection after GLC separation with a 30% SE-30 column. The unusually heavy liquid phase loading is necessary to eliminate irreversible adsorption on the solid support. The electron-capture detector provides excellent sensitivity and specificity because of the electronegative nature of the nitric ester. The method was used to study the blood levels of isosorbide dinitrate and two metabolites in four beagle dogs after single oral doses of 40 mg of isosorbide dinitrate and in two human volunteers after a sublingual dose of 10 mg of isosorbide dinitrate.
The hemodynamic response to nitroglycerin administration, to sublingual or oral administration of isosorbide dinitrate, or to a placebo was evaluated and compared in 37 patients with unstable angina pectoris under resting, pain-free conditions. Patients with congestive heart failure were not included in this study. Serial measurements of mean arterial blood pressure (MAP), pulmonary arterial end-diastolic pressure (PAEDP), cardiac index (CI), and heart rate (HR) were obtained for one hour following nitroglycerin administration and for four hours following sublingual or oral administration of isosorbide dinitrate. Echocardiographic end-diastolic volume (EDV) measurements were obtained for the groups receiving isosorbide dinitrate or placebo. There was a significant (P less than 0.05 or less than 0.1) reduction of the MAP (5 to 10 mm Hg) that persisted for more than four hours following both sublingual and oral administration of isosorbide dinitrate. The changes in the PAEDP, HR, and CI following sublingual or oral administration of isosorbide dinitrate were small and not significant. In the group receiving isosorbide dinitrate sublingually, the EDV was reduced by more than 30 ml below the placebo group (P less than 0.1) for up to four hours. The effects of nitroglycerin administration were similar in magnitude but of much shorter duration (three to four hours for sublingual and oral administration of isosorbide dinitrate vs 15 to 30 minutes for nitroglycerin). These data demonstrate that the duration of the hemodynamic effects of sublingually and orally administered isosorbide dinitrate in patients with unstable angina pectoris and normal resting hemodynamics is 8 to 12 times longer than that of nitroglycerin.
A GLC method for the determination of plasma isosorbide dinitrate using electron-capture detection is described. The organic nitrates are especially suited for electron-capture detection if the detector temperature is optimized for maximum sensitivity, e.g., 175 degrees. Proper maintenance of the detector and column assures reproducible data in the low nanogram range. The extraction procedure described is simple, efficient, and expedient for processing large numbers of samples. The method was used to study plasma levels in four human volunteers after a single dose of a 5-mg chewable isosorbide dinitrate tablet. Concentration levels of isosorbide dinitrate as low as 0.5 ng/ml of plasma can be measured by this procedure.
The efficacy of oral isosorbide dinitrate was evaluated in nine hospitalized patients with chronic angina pectoris and positive maximal bicycle exercise tests. Patients were randomized double-blind to receive either 20 mg of isosorbide dinitrate or placebo on successive days after a control maximal upright bicycle exercise test. On each day hourly exercise tests were performed for 4 hours after drug administration to an end point of fatigue or angina pectoris. Mean systolic blood pressure 4 hours after the administration of isosorbide dinitrate was 25 mm Hg less than the control value (P less than 0.001). The values for resting heart rate and exercise-attained heart rate-blood pressure product were not significantly different from the values after placebo. The duration of exercise was prolonged (P less than 0.025) for at least 3 hours, and less ST depression (P less than 0.01) was observed up to 3 hours after the administration of isosorbide dinitrate compared with control values. The demonstration of sustained imporved exercise performance and previously described hemodynamic effects with the use of higher doses suggests that adequate blood levels of isosorbide dinitrate or mononitrate metabolites may be important for the efficacy of oral organic nitrates.
The effect of isosorbide dinitrate, a nitrovasodilator known to inhibit platelet function, was examined in a model of electrically induced carotid artery thrombosis in rats. In the dose range of 1-30 mg/kg isosorbide dinitrate, administered orally, significantly delayed carotid occlusion. These results demonstrate that isosorbide dinitrate has antithrombotic activity and it is suggested that this antithrombotic activity is due to the generation of nitric oxide.
A new galenic form of isosorbide dinitrate (consisting of a hydrophilic matrix which allows very slow release of the active drug) was studied from the pharmacokinetic and pharmacodynamic view points in 11 patients with stable angina pectoris under betablocker therapy. After testing their sensitivity to nitrates with a sublingual trinitrin test causing a fall greater than or equal to 20 mmHg in systolic and greater than or equal to 10 mmHg in diastolic blood pressure, the patients were given a single tablet of Risordan LP 80 daily for 7 days. The equilibrium plasma concentrations of isosorbide dinitrate and its mononitrate metabolites (2-isosorbide mononitrate and 5-isosorbide mononitrate) over 24 hours were measured on the 6th treatment day. A method of measuring these nitrate derivatives has been developed and validated. The concentrations measured enabled the study of the pharmacokinetics of this new form, showing an average minimal concentration of 5-isosorbide mononitrate (principal metabolite) of 85 +/- 41 micrograms/l and an amplitude of fluctuation over the 24 hours period of 296 +/- 102 micrograms/l. From the pharmacodynamic point of view, the evaluation of the sensitivity to a single dose of 0.75 mg of trinitrin 24 hours after the first dose of Risordan LP 80, just before the second dose and 24 hours after the seventh dose, showed a significant difference (average decrease of 40 +/- 19 mmHg in systolic blood pressure) with respect to the values observed during the selection phase.(ABSTRACT TRUNCATED AT 250 WORDS)
To evaluate whether there is cross-tolerance to the circulatory effects of isosorbide dinitrate and nitroglycerin, six subjects were given 120 mg/day of sustained-action isosorbide dinitrate in three divided doses for six to eight weeks. Prior to and during the last week of long-term isosorbide dinitrate administration, the effects of sublingually given nitroglycerin (0.9 mg) on plethysmographically measured calf blood flow and venous volume at 30 mm Hg (VV[30]) were measured on three occasions and averaged. Although the arteriolar dilation produced by nitroglycerin was unaltered by isosorbide dinitrate, the venodilation was significantly attenuated. The VV[30] increased from 3.00 to 3.28 ml/100 ml (P less than .02) with nitroglycerin prior to isosorbide dinitrate administration, but failed to increase with nitroglycerin during the long-term administration of isosorbide dinitrate (2.95 to 2.95 ml/100 ml, P greater than .5).