Isosorbide Mononitrate is indicated for the prevention and management of angina pectoris associated with coronary artery disease. However, due to its relatively slow onset of action when taken orally, it is not suitable for the immediate relief of acute anginal attacks.

Isosorbide Mononitrate is the main active metabolic of isosorbide dinitrate (ISDN), and much of the pharmacological effect of the dinitrate is due to this metabolite. Its primary action is relaxation of vascular smooth muscle, leading to dilation of peripheral veins and arteries, particularly the veins. Venous dilation results in pooling of blood in the peripheral circulation, which reduces venous return to the heart. This, in turn, lowers left ventricular end-diastolic pressure and pulmonary capillary wedge pressure (preload). Arterial dilation reduces systemic vascular resistance, systolic blood pressure, and mean arterial pressure (afterload). Additionally, dilation of coronary arteries also occurs. The relative contribution of preload reduction, afterload reduction, and coronary vasodilation to its therapeutic effect is not fully defined.

Tablet: The usual oral dose is 1 tablet (20 mg) 2 times daily, first dose in the morning and another 7 hours apart. Although maintenance doses ranging from 20 mg to 120 mg (1-6 tablets), a dose of 10 mg (1/2 tablet) is suitable when lower dosage is used at the starting of treatment or as directed by a registered physician.

Sustained Release Capsule: The usual oral dose is 1 capsule (50 mg) daily or as directed by the registered physician.

• Concomitant use of Isosorbide Mononitrate with phosphodiesterase (PDE) inhibitors in any form is contraindicated
• Concomitant use with riociguat (a soluble guanylate cyclase stimulator) is also contraindicated
• The vasodilatory effect of Isosorbide Mononitrate may be enhanced when used with other vasodilators; alcohol may further potentiate this effect
• Significant orthostatic hypotension has been observed when used with calcium channel blockers or other organic nitrates; dose adjustment may be required

Isosorbide Mononitrate is contraindicated in patients with known hypersensitivity to the drug. It should not be used in patients taking phosphodiesterase inhibitors (such as sildenafil, tadalafil, or vardenafil) due to the risk of severe hypotension, syncope, or myocardial ischemia. Concomitant use with riociguat is also contraindicated as it may lead to significant hypotension.

Common adverse effects include headache, dizziness, and occasional hypotension.

Pregnancy (Category B): Animal studies (in rats and rabbits at doses up to 540 and 810 mg/kg/day) have not demonstrated fetal harm; however, adequate and well-controlled studies in pregnant women are lacking. Therefore, Isosorbide Mononitrate should be used during pregnancy only if clearly necessary.

Lactation: It is not known whether Isosorbide Mononitrate is excreted in human breast milk. As many drugs are excreted in breast milk, caution should be exercised when administered to nursing mothers.

Severe hypotension may occur, particularly in the upright position, even with low doses of isosorbide mononitrate. Caution is advised in patients who are volume-depleted or already hypotensive. Hypotension may be accompanied by paradoxical bradycardia and worsening angina.

Nitrate therapy may worsen angina in patients with hypertrophic cardiomyopathy. In individuals with prolonged exposure to organic nitrates, tolerance may develop, and abrupt withdrawal may lead to chest pain, myocardial infarction, or even sudden death, indicating possible physical dependence. The clinical significance of these findings in routine use remains uncertain.

Patients should be instructed to follow the prescribed dosing schedule carefully (typically two doses about 7 hours apart) to maintain the antianginal effect.

Headache is a common effect of nitrate therapy and may indicate drug activity. Patients should not discontinue or alter therapy solely due to headache, as this may reduce therapeutic benefit. Headaches can often be relieved with mild analgesics such as aspirin or acetaminophen without affecting efficacy.

Lightheadedness or dizziness may occur when standing, especially after rising from a sitting or lying position, and may be more pronounced with alcohol use.

Symptoms: Common symptoms of overdose include hypotension, throbbing headache, tachycardia, and flushing. Severe cases may result in methemoglobinemia.

Treatment: Management includes placing the patient in a supine position and administering fluids. Alpha-adrenergic vasopressors may be required. Methemoglobinemia should be treated with intravenous methylene blue (1–2 mg/kg).

Nitrates: Coronary vasodilators

Store at a temperature between 20°C and 30°C.