Isosorbide-5-mononitrate is an active metabolite of isosorbide dinitrate. It is a vasodilator with effects on both arteries and vein and also coronary vessels. It causes reduction of preload and afterload and redistributes coronary flow to ischemic regions.
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The recommended regimen of Isosorbide Mononitrate tablets is 20 mg (one tablet) twice daily, with the two doses given 7 hours apart. For most patients, this can be accomplished by taking the first dose on awakening and the second dose 7 hours later. Dosage adjustments are not necessary for elderly patients or patients with altered renal or hepatic function.
Multiple studies of organic nitrates have shown that maintenance of continuous 24-hour plasma levels results in refractory tolerance. The dosing regimen for Isosorbide Mononitrate tablets provides a daily nitrate-free interval to avoid the development of this tolerance. Well-controlled studies have shown that tolerance to Isosorbide Mononitrate tablets is avoided when using the twice-daily regimen in which the two doses are given 7 hours apart. This regimen has been shown to have antianginal efficacy beginning 1 hour after the first dose and lasting at least 5 hours after the second dose. The duration (if any) of antianginal activity beyond 12 hours has not been studied; large controlled studies with other nitrates suggest that no dosing regimen should be expected to provide more than about 12 hours of continuous antianginal efficacy per day.
In clinical trials, Isosorbide Mononitrate tablets have been administered in a variety of regimens. Single doses less than 20 mg have not been adequately studied, while single doses greater than 20 mg have demonstrated no greater efficacy than doses of 20 mg.