Drug Groups

approved

Description

Isosorbide mononitrate is a drug used principally in the treatment of angina pectoris[1] and acts by dilating the blood vessels so as to reduce the blood pressure. It is sold by AstraZeneca under the trade name Imdur.

Isosorbide mononitrate is used to for the the prophylactic treatment of angina pectoris; that is, it is taken in order to prevent or at least reduce the occurrence of angina. Research on Isosorbide mononitrate as a cervical ripener to reduce time at hospital to birth is supportive.

Isosorbide mononitrate is an active metabolite of isosorbide dinitrate and exerts qualitatively similar effects. Isosorbide mononitrate reduces the workload of the heart by producing venous and arterial dilation. By reducing the end diastolic pressure and volume, isosorbide mononitrate lowers intramural pressure, hence leading to an improvement in the subendocardial blood flow. The net effect when administering isosorbide mononitrate is therefore a reduced workload for the heart and an improvement in the oxygen supply/demand balance of the myocardium.

The adverse reactions which follow have been reported in studies with isosorbide mononitrate:
Very common. Headache predominates (up to 30%) necessitating withdrawal of 2 to 3 % of patients, but the incidence reduces rapidly as treatment continues .
Common. Tiredness, sleep disturbances (6%) and gastrointestinal disturbances (6%) have been reported during clinical trials with isosorbide mononitrate modified release tablets, but at a frequency no greater than for placebo. Hypotension (4 to 5%), poor appetite (2.5%), nausea (1%).
Adverse effects associated with the clinical use of the drug are as expected with all nitrate preparations. They occur mainly in the early stages of treatment.
Hypotension (4%) with symptoms such as dizziness and nausea (1%) have been reported. These symptoms generally disappear during long-term treatment.
Other reactions that have been reported with isosorbide mononitrate modified release tablets include tachycardia, vomiting, diarrhoea, vertigo and heartburn

Indication

For the prevention of angina pectoris due to coronary artery disease and the treatment of acute and chronic angina pectoris, hypertension, and myocardial infarction.

Pharmacology

Isosorbide-5-mononitrate, the long-acting metabolite of isosorbide dinitrate, is used as a vasodilatory agent in the management of angina pectoris. By dilating the vessels, it lowers the blood pressure and reduces the left ventricular preload and afterload, therefore, leads to a reduction of myocardial oxygen requirement.

Toxicity

Symptoms of overdose include vasodilatation, venous pooling, reduced cardiac output, and hypotension. There are no data suggesting what dose of isosorbide mononitrate is likely to be life-threatening in humans. In rats and mice, there is significant lethality at doses of 2000 mg/kg and 3000 mg/kg, respectively.

Affected Organisms

Biotransformation

Hepatic

Absorption

100%

Half Life

5 hours

Protein Binding

5%

Elimination

Isosorbide mononitrate is primarily metabolized by the liver, but unlike oral isosorbide dinitrate, it is not subject to first-pass metabolism.
Isosorbide mononitrate is cleared by denitration to isosorbide and glucuronidation as the mononitrate, with 96% of the administered dose excreted in the urine within 5 days and only about 1% eliminated in the feces. At least six different compounds have been detected in urine, with about 2% of the dose excreted as the unchanged drug and at least five metabolites.

Distribution

* 0.6 to 0.7 L/kg

Clearance

* 120–122 mL/min [Single dose of 60 mg PO]
* 151–187 mL/min [Single dose of extended-release tablet 60 mg PO]
* 132-151 mL/min [Multiple doses of extended release tablet 60 mg PO]
* 119-140 mL/min [Multiple doses of extended release tablet 120 mg PO]

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