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Concentrations of isosorbide dinitrate, isosorbide-2-mononitrate and isosorbide-5-mononitrate in human vascular and muscle tissue under steady-state conditions.

The concentrations of isosorbide dinitrate (ISDN), isosorbide-5-mononitrate (IS-5-MN) and isosorbide-2-mononitrate (IS-2-MN) were determined in plasma (PL), saphenous vein wall (SV) and pectoral muscle (PM) from 8 patients undergoing coronary bypass surgery. The patients were pretreated for 2 days with ISDN 240 mg per day (standard release formulation) in 4 doses of 40 mg and one dose of 80 mg. The plasma and tissue samples were obtained during the operation, 10-12 h after the last dose. Isosorbide-2-mononitrate and isosorbide-5-mononitrate were present in plasma and tissues in the same concentration ranges with molar concentration ratios of 0.88 (IS-2-MN: PM/PL), 0.85 (IS-5-MN: PM/PL), 0.99 (IS-2-MN: SV/PL) and 1.06 (IS-5-MN: SV/PL). Mean ISDN concentrations in tissue were considerably higher than in plasma; the molar concentration ratios were 4.9 (SM/PL) and 7.21 (SV/PL). The accumulation of ISDN in vessel walls may contribute to its greater vascular action compared to the mononitrates, but it may also facilitate the development of tolerance during long-term treatment.

Aged↗

Saliva concentrations of isosorbide dinitrate, isosorbide 2-mononitrate and isosorbide 5-mononitrate.

Correlations between saliva and plasma concentrations of isosorbide dinitrate (ISDN), and its active metabolites, isosorbide 2-mononitrate (2-ISMN) and isosorbide 5-mononitrate (5-ISMN) were examined. In the case of 5-ISMN (r = 0.98, P less than 0.01), saliva concentrations are probably reliable indices of the plasma concentrations of this drug and their measurement should provide a useful non-invasive procedure to assess compliance during the clinical use of products containing either ISDN or 5-ISMN: it may also be helpful in assessing the clinical pharmacokinetics of 5-ISMN. Less satisfactory correlations were obtained for ISDN (r = 0.84) and 2-ISMN (r = 0.83).

Adult↗

Pharmacokinetics of isosorbide dinitrate, isosorbide-2-nitrate and isosorbide-5-nitrate in renal insufficiency after repeated oral dosage.

The pharmacokinetics of isosorbide dinitrate (ISDN) and its two active metabolites isosorbide-2-nitrate (IS-2-N) and isosorbide-5-nitrate (IS-5-N) were studied in 20 patients with normal and impaired renal function after repeated oral doses of standard 20 mg tablets ISDN t.i.d. Blood samples were taken in the steady-state on days 2 and 14, and the plasma concentrations were measured by electron capture capillary gas chromatography. We found a wide variation of pharmacokinetic parameters (AUCss0-8 and t1/2) of ISDN, IS-2-N, and IS-5-N in our patients. No correlation was detected between AUCss0-8 or t1/2 and the degree of renal insufficiency. No drug accumulation was observed after 14 days of administration.

Administration, Oral↗

Pain scoring--a method for assessing acute antianginal therapy comparison of the response to acute sublingual administration of an isosorbide dinitrate tablet, isosorbide dinitrate spray and nitroglycerin spray in unstable angina.

It is difficult to assess acute therapeutic intervention therapy, particularly in patients with unstable angina. Our aim was to evaluate the feasibility of a pain-scoring method and to compare the response to sublingual administration of an isosorbide dinitrate (ISDN) tablet, ISDN spray or nitroglycerin (NTG) spray. Pain scoring was assessed by the subjective grading of the patients' pain severity from 1 to 10. We studied 205 patients (mean age 66 +/- 13 years). Pain attenuation, defined as at least 50% reduction in pain intensity, occurred in the ISDN tablet, ISDN spray and NTG spray groups after 360 +/- 290, 318 +/- 289 and 233 +/- 271 s, respectively (p = 0.0005). In conclusion, pain scoring is a feasible and useful clinical method to assess antianginal therapy in unstable angina patients. Sublingual nitrate sprays, particularly NTG, seem to alleviate anginal pain faster than ISDN tablets in this patient population.

Administration, Inhalation↗

Polarographic determination of isosorbide dinitrate.

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.

Autoanalysis↗

Nitrates: why and how should they be used today? Current status of the clinical usefulness of nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate.

Nitrates are highly effective both in terminating acute attacks of angina pectoris and in the prophylaxis of symptomatic and asymptomatic myocardial ischemia. Preload reduction by venodilatation is the prevailing mechanism of nitrates in patients with chronic stable angina and is the unique feature distinguishing them from beta and calcium-channel blockers. Nitrates dilate coronary arteries not only in pre- and poststenotic vessels, but also in eccentric lesions. In patients with endothelial dysfunction, nitrates seem to be the physiological substitute for endothelium-derived relaxing factor. During the past decade, however, there has been substantial evidence of a clinically relevant loss of the anti-ischemic effects ("nitrate tolerance"). Many studies with oral dosing of isosorbide dinitrate or isosorbide-5-mononitrate at least three times daily have proven nitrate tolerance in patients with coronary artery disease and/or congestive heart failure. Complete loss of anti-ischemic effects after repetitive, continuous patch attachments has also been found. As we first showed in 1983, intermittent therapy with once-daily ingestion of high-dose sustained-release isosorbide dinitrate was successful in preventing the development of tolerance. Similarly, tolerance to isosorbide-5-mononitrate also does not develop when it is ingested once daily. It is now generally accepted that a daily low-nitrate interval is required to prevent tolerance development. Although the minimal patch-free interval required to prevent tolerance needs further investigation, a 12-h patch-free interval should prevent tolerance in most patients. The prolonged duration of action of once-daily high-dosage administration of sustained-release formulations, the improved patient compliance with a single daily administration, and the increased likelihood of maximal anti-ischemic effects are important reasons for recommending high single daily doses of isosorbide dinitrate or isosorbide-5-mononitrate.

Angina Pectoris↗

Inactivation of human aldehyde dehydrogenase by isosorbide dinitrate.

Isosorbide dinitrate inactivated E1 and E2 isozymes of human aldehyde dehydrogenase (EC 1.2.1.3), abolishing both dehydrogenase and esterase activities. NAD promoted, whereas chloral and NAD protected the enzyme from inactivation. The inactivation was irreversible upon dialysis and occurred without incorporation of the 14C-labeled isosorbide dinitrate. Inactivation was associated with formation of products, isosorbide-2-mononitrate and isosorbide-5-mononitrate. At 25 degrees C there were two pathways of product formation: a fast pathway, sensitive to aldehyde dehydrogenase inhibitors, and a slower pathway insensitive to inhibitors. The fast product formation and inactivation occurred simultaneously, and both were inhibited by chloral and by the irreversible active site-directed inhibitor bromoacetophenone. At 0 degree C the slow product formation was abolished, allowing study of the enzyme catalyzed reaction. The inactivation of the E1 isozyme at 0 degree C occurred in a single turnover that accounted for 80% of catalytic activity loss with isosorbide-2-mononitrate being the major product. No nitrate was ever detected; at 25 degrees C, nitrite was detected but in less than stoichiometric amounts. The mononitrates were also substrates and inactivators of aldehyde dehydrogenase. Isosorbide-2-mononitrate had the lowest K(i) and k3 values for the E1 isozyme when compared with that of the other two nitrate esters of isosorbide. Reversibility of inactivation by 2-mercaptoethanol suggested involvement of enzyme sulfhydryls. The inactivation appears to be mechanism-based and involves the esterase function of aldehyde dehydrogenase.

Aldehyde Dehydrogenase↗

Plasma levels of isosorbide dinitrate and the isosorbide mononitrates after increasing doses of a retard preparation of isosorbide dinitrate.

Different doses of a retard preparation of isosorbide dinitrate (40, 80 and 120 mg) were given in a cross-over design with one week intervals to 6 patients with angina pectoris. Plasma concentrations of isosorbide dinitrate and of the isosorbide 2- and 5-mononitrates were measured by a gas-liquid chromatographic method. The concentrations of isosorbide dinitrate rose with the dose given, and with the highest dose, levels above 5 ng/ml were obtained for 12 hours. Concentrations of the mononitrates were much higher than those of the parent compound.

Angina Pectoris↗

Nitro compounds (isosorbide dinitrate, 5-isosorbide mononitrate and glyceryl trinitrate) on the femoral vein and femoral artery.

In organ bath studies, the selectivity of isolated femoral vein and artery of rabbit to isosorbide dinitrate (ISDN), 5-isosorbide mononitrate (ISMN), major metabolite of ISDN, and glyceryl trinitrate (GTN) was compared. The femoral vein and artery contracted by norepinephrine were relaxed by all the nitro compounds dose-dependently. Potency order was GTN greater than ISDN greater than ISMN. The maximum inhibitory responses to the nitrocompounds and their pIC50 values (negative logarithms of doses to induce the 50% response) were greater in the femoral vein than in the femoral artery. For ISMN a 3 times greater sensitivity of femoral vein than of femoral artery was found.

Animals↗

Effects of nitro compounds, isosorbide dinitrate, 5-isosorbide mononitrate and glyceryl trinitrate on Ca-uptake into Ca-stores and Ca-release from Ca-stores in rabbit isolated femoral veins and femoral arteries.

In organ bath studies, effects of isosorbide dinitrate (ISDN), 5-isosorbide mononitrate (ISMN), a major metabolite of ISDN, and glyceryl trinitrate (GTN) on Ca-uptake into Ca-stores and Ca-release from Ca-stores were tested in the rabbit isolated femoral veins and femoral arteries. ISDN (10(-4) M) and GTN (10(-4) M) inhibited Ca-uptake in the femoral veins but not in the femoral arteries. The selectivity to the femoral veins was not observed in ISMN (10(-3) M) and GTN (3 X 10(-6) M). All the nitro compounds inhibited Ca-release from Ca-stores more effectively in the femoral veins than in the femoral arteries. The present results may explain the selectivity of the nitro compounds to the femoral veins.

Animals↗

Effect of pertussis toxin and the cGMP lowering agent LY83583 on the relaxation induced by nitrates in isolated bovine mesenteric artery. A comparison between glyceryl trinitrate, isosorbide dinitrate and isosorbide 5-mononitrate.

The effect of pertussis toxin (PTX) and the cyclic GMP-lowering agent LY83583 on the relaxatory response induced by glyceryl trinitrate (GTN), isosorbide dinitrate (ISDN) and isosorbide-5-mononitrate (ISMN) in bovine mesenteric artery was investigated. Pretreatment with PTX (100 ng/ml; 2h) induced a 100-fold right shift of the concentration-effect curve for GTN, while no effect on the relaxatory response elicited by ISDN and ISMN was seen 10 microM LY83583 markedly reduced the relaxatory effect of all the organic nitroesters. Based on the different sensitivity towards PTX it is suggested that GTN induces vascular smooth muscle relaxation by a partly different mechanism than ISDN and ISMN. However, cGMP seems to play a crucial role in mediating the relaxatory response of all the tested organic nitroesters since LY83583 profoundly suppressed the relaxatory response.

Aminoquinolines↗