Side Effects of Monoket (isosorbide mononitrate)

Monoket (isosorbide mononitrate) is a nitrate used to treat and prevent angina pectoris or "heart pain." 

Nitrates are vasodilators (dilators of blood vessels). Blood returning from the body in the veins must be pumped by the heart through the lungs and into the body's arteries against the high pressure in the arteries. 

In order to accomplish this, the heart's muscle must produce and use energy which requires oxygen brought to the heart by the blood. Angina is due to an inadequate flow of blood (and oxygen) to the muscle of the heart. 

Nitrates correct the imbalance between the flow of blood and oxygen to the heart and the work that the heart must do by dilating the arteries and veins in the body. Dilation of the veins reduces the amount of blood that returns to the heart that must be pumped. Dilation of the arteries lowers the pressure in the arteries against which the heart must pump. 

As a consequence of both effects, the heart works less and requires less blood and oxygen.

Common side effects of Monoket include

• headaches,
• flushing, and
• a severe drop in blood pressure when rising from a sitting position, causing dizziness, palpitations, and weakness.

Serious side effects of Monoket include methemoglobinemia (rare). 

Drug interactions of Monoket include sildenafil, tadalafil, avanafil, and vardenafil, which increase the blood pressure lowering effects of Monoket and may cause excessive reductions in blood pressure. 

Severe reductions in blood pressure, especially when changing posture (orthostatic hypotension), may occur when Monoket is combined with calcium channel blockers, which also reduce blood pressure. 

There are no adequate studies of Monoket in pregnant women. 

It is unknown if Monoket is excreted in breast milk. Consult your doctor before breastfeeding.

Headaches are the most common side effect of isosorbide mononitrate and usually are dose related (increase with higher doses). Flushing may occur because isosorbide mononitrate dilates (enlarges) blood vessels. Isosorbide mononitrate may cause a severe drop in blood pressure when rising from a sitting position, causing: 

• dizziness,
• palpitations, and
• weakness.

To reduce the risk of low blood pressure, patients should rise slowly from a sitting position.

Headache is the most frequent side effect and was the cause of 2% of all dropouts from controlled-clinical trials. Headache decreased in incidence after the first few days of therapy.

The following table shows the frequency of adverse reactions observed in 1% or more of subjects in 6 placebo-controlled trials, conducted in the United States and abroad. The same table shows the frequency of withdrawal for these adverse reactions. In many cases the adverse reactions were of uncertain relation to drug treatment.

Frequency Of Adverse Reactions (Discontinuations)*

Other adverse reactions, each reported by fewer than 1% of exposed patients, and in many cases of uncertain relation to drug treatment, were:

Cardiovascular: acute myocardial infarction, apoplexy, arrhythmias, bradycardia, edema, hypertension, hypotension, pallor, palpitations, tachycardia.

Dermatologic: sweating.

Gastrointestinal: anorexia, dry mouth, dyspepsia, thirst, vomiting, decreased weight.

Genitourinary: prostatic disorder.

Miscellaneous: amblyopia, back pain, bitter taste, muscle cramps, neck pain, pares thesia, susurrus aurium.

Neurologic: anxiety, impaired concentration, depression, insomnia, nervousness, nightmares, restlessness, tremor, vertigo.

Respiratory: asthma, dyspnea, sinusitis.

Extremely rarely, ordinary doses of organic nitrates have caused methemoglobinemia in normal-seeming patients; for further discussion of its diagnosis and treatment see the prescribing information.

Concomitant use of Monoket with phosphodiesterase inhibitors in any form is contraindicated.

Concomitant use of Monoket with riociguat, a soluble guanylate cyclase stimulator, is contraindicated.

The vasodilating effects of isosorbide mononitrate may be additive with those of other vasodilators. Alcohol, in particular, has been found to exhibit additive effects of this variety.

Marked symptomatic orthostatic hypotension has been reported when calcium channel blockers and organic nitrates were used in combination. Dose adjustments of either class of agents may be necessary.