1 What is Isoket?

Brand: Isoket, Imdur, Imdur ER, Ismo, Monoket

Generic: Isosorbide mononitrate

Isoket is a drug that dilates blood vessels so the heart can pump blood more easily. Doctors prescribe Isosorbide mononitrate to prevent angina attacks (chest pains). Angina is caused by low blood supply to the heart muscles due to obstruction or tightness of blood vessels around the heart.

Long-term use of Isosorbide mononitrate prevents angina. It belongs to a class of drugs called nitrates, which work by relaxing blood vessels in the body that ease the workload of the heart while increasing the supply of blood and oxygen.

Isosorbide mononitrate is not appropriate for angina that has already begun. Isosorbide mononitrate is a prescription drug.

2 What to Know Before Using

Before using Isoket, you must know all about the risks and complications associated with it.

The doctor may consider the following before prescribing Isosorbide mononitrate:

Tell your doctor if you have allergies or unusual reactions to drugs. Isosorbide mononitrate is closely related to butyl nitrate, amyl nitrate, and nitrites. If you have allergies to nitrites, you may experience allergies to Isosorbide mononitrate too.

You also need to mention allergies to other things like food, drink, animal products or dyes.

Pediatric and Geriatric use:
The safety and efficacy of Isosorbide mononitrate in pediatric patients (individuals below 21 years of age) have not been established.

Pregnancy and breastfeeding:
Isosorbide mononitrate is an FDA pregnancy category B drug, which means that animal studies show it does not harm the fetus and have not shown adverse risk in studies in pregnant women.

There are no adequate studies showing that isosorbide mononitrate causes harm to infants nursing from mothers using the medication. The doctor will weight benefits and possible risks before prescribing isosorbide mononitrate to pregnant and breastfeeding women.

Tobacco, alcohol, and food:
Isosorbide mononitrate may interact with tobacco and alcohol. Tobacco and alcohol also increase the risk of complications from heart disease. Tell your doctor if you smoke or drink alcohol when using Isosorbide mononitrate.

Interactions with Medicines:
Isosorbide mononitrate can interact with certain medications especially those used to treat erectile dysfunction and pulmonary hypertension. Do not take Isosorbide mononitrate if you are taking these medicines:

  • Sildenafil (Viagra, Revatio)
  • Taladafil (Cialis, Adcirca)
  • Riociguat (Adempas)
  • Avanafil (Stendra)
  • Vardenafil (Levitra, Staxyn)

Taking these medicines with Isosorbide mononitrate can cause serious side effects.

Medical conditions:
Isosorbide mononitrate is not appropriate for certain medical conditions. Do not take the drug if you have the following conditions:

Isosorbide mononitrate may worsen these conditions. Also, do not take Isosorbide mononitrate if you experienced allergies from other nitrate drugs, nitrates, and amyl nitrate and butyl nitrate.

3 Proper Usage

To use Isoket properly, you must follow all instructions given by your doctor.

Your doctor will give you instructions on taking Isosorbide mononitrate. Always follow these instructions and observe proper dose – do not take more or less than the prescribed dose. Isosorbide mononitrate must be taken first thing in the morning, preferably at the same schedule everyday.

There is the extended-release version that lasts for 8 to 10 hours. Take it with a half glass of water and take care not to chew, crush or split the tablet.

The doctor may institute ‘drug-free’ periods where you will not take the medication for a time, which will improve the effects of Isosorbide mononitrate.

Isosorbide mononitrate works to reduce the likelihood of angina attacks for a long time, and it will not relieve angina that has already started. If you already have angina, Isosorbide mononitrate will not work and you need to take other drugs or go to the hospital. Talk to your doctor if you need a fast-acting drug to relieve angina.

For prevention of angina, Isosorbide mononitrate is given in the following doses:


  • For extended-release tablets, starting dose is 30 mg to 60 mg once a day. The doctor may increase the dose as needed. The tablet is taken after arising in the morning.
  • For tablets, starting dose is 20 mg twice daily. The first tablet is taken after arising in the morning, and the second dose is take 7 hours later.


  • The dose for children must be determined by the doctor.

Missed dose:
If you missed a dose, take it as soon as you remember. If it is almost time for the next dose, you have to skip the missed dose. Do not increase the dose to make up for the missed dose.

Store Isosorbide mononitrate at room temperature, away from heat, light and moisture. Do not store in the freezer.

Dispose outdated and expired tablets immediately. Ask your pharmacist or doctor for help in disposing of the tablets.
Keep out of reach of children.

4 Precautions to Take

Before using Isoket, there are some precautions you must take.

When taking Isosorbide mononitrate treatment for a long time, it is important that your blood pressure levels be regularly monitored. Always stick to scheduled clinic appointments so the doctor will know if the medication is working properly. You may have to have blood tests to determine adverse effects of the drug.

Certain medications are not good for you if you are taking Isosorbide mononitrate. Do not take riociguat (Adempas®), sildenafil (Viagra®), tadalafil (Cialis®), or vardenafil (Levitra®). These medicines can reduce your blood pressure to dangerously low levels, which can cause blurred vision, dizziness, lightheadedness, or fainting. Very low blood pressure can also cause angina. If you experience chest pain, go to the hospital immediately.

Isosorbide mononitrate is known to cause headaches since reduced blood pressure may temporarily reduce blood supply to the brain. Thus, headaches are normal and a sign that the medication is working properly. Do not skip or avoid taking the medication because of headaches. If headaches seem severe or are accompanied by other symptoms, call your doctor.

Taking Isosorbide mononitrate may cause lightheadedness, dizziness or fainting when trying to get up from the bed or a chair. You can reduce dizziness or avoid fainting by arising very slowly and gradually.

If you drink alcohol, you have to limit your intake while taking Isosorbide mononitrate. Alcohol can increase the risk of lightheadedness and fainting. Certain things like hot weather, standing up for extended periods of time and prolonged exercise can also make you faint or lightheaded. Make sure to exercise extra care.

Do not stop taking Isosorbide mononitrate without doctor’s orders. Isosorbide mononitrate is usually tapered off before stopping completely to prevent side effects. Also, abrupt cessation may cause side effects.

Before having treatment from another doctor, or having dental work, make sure they know you are taking Isosorbide mononitrate. Note that some lab tests require you to stop taking the medication for several days. Call your prescribing doctor before having these lab tests.

It is important you do not take other medications or supplements while taking Isosorbide mononitrate unless you call your doctor first. This includes herbal products, multivitamins, and over-the-counter medications.

5 Potential Side Effects

As with many medications, there are several potential side effects associated with Isoket.

Some of the side effects of Isosorbide mononitrate are serious and require doctor’s attention, such as:

Less common

  • Reduced control in body movement
  • Pain in the arms, jaws, back or neck
  • Pain, tension and weakness during exertion, which is relieved by rest
  • Pain in the bladder area
  • Having black, tarry stools
  • Bleeding during and after defecation
  • Bleeding gums
  • Traces of blood in the urine or pink-colored urine
  • Chest pain and feeling of unease or discomfort
  • Body aches
  • Burning sensation or difficulties while urinating
  • Chest tightness or heaviness
  • Tingling sensation, feeling of ‘pins and needles’, itching, numbness, burning or crawling sensation anywhere in the body, especially in the lips, hands or feet
  • Having chills
  • Cold sweats or sudden sweating
  • Having colds
  • Confusion
  • Convulsions
  • Cough
  • Hoarseness
  • Decreased urine output
  • Or, having large amount of pale or diluted urine
  • Diarrhea
  • Labored or difficulties in breathing
  • Irregular breathing
  • Noticeably dilated veins in the neck
  • Dizziness, faintness and lightheadedness when getting up suddenly
  • Dryness of mouth
  • Ear congestion
  • Fever with chills
  • Having flu-like symptoms
  • Frequent urinating or urgency
  • Malaise, or general feeling of being ill or sick
  • Headache, or having severe or throbbing headache
  • Having itching, redness or swelling, or presence of sores in one or both legs
  • Swelling, stiffness or pain in the joints
  • Loss of voice
  • Reduced or loss of appetite
  • Pain in the stomach, flanks or back
  • Muscle cramps, aches, and pains
  • Nasal congestion or a runny nose
  • Nausea and vomiting
  • Pain or partial paralysis
  • Having pinpoint red or purple spots on the skin
  • Sensation of pounding in the ears
  • Shakiness, trembling or shivering of the whole body, or arms, hands or feet
  • Frequent sneezing
  • Sudden reduction of urine output
  • Swelling of the hands, fingers, feet or lower legs
  • Swelling anywhere in the body
  • Insomnia
  • Presence of swelling around the anus
  • Unusual bleeding or bruising
  • Unexplained fatigue or tiredness
  • Vomiting of blood, or material that looks like coffee grounds (blood clots)
  • Weakness
  • Unintended weight gain
  • Anxiety or nervousness
  • Having heart murmurs
  • Changes in heart rate, like too slow, too fast or irregular
  • Abnormal heart sounds or having extra heartbeats
  • Rare side effects
  • Bluish discoloration of the lips, fingernails and palms
  • Dark color of urine
  • Paleness of skin
  • Rapid or fluttering heart rate
  • Here are the symptoms of Isosorbide mononitrate overdose. Get immediate medical help if you have the following:
  • Changes in vision, like double, blurring or loss of vision
  • Changes in consciousness
  • Changes in discerning colors or color perception, especially blue or yellow
  • Cold clammy skin
  • Disturbed perception, like feeling of constant movement of the body or surroundings
  • Seeing halos around lights
  • Severe and throbbing headache
  • Loss of consciousness
  • Night blindness
  • Sensitivity from light
  • Sensation of spinning
  • Tunnel vision
  • Paralysis

Here are uncommon and less serious side effects of Isosorbide mononitrate. These side effects are caused by the body’s adjustment to the medication, so usually there is no need for medical attention. These side effects tend to lessen over time:

  • Hyperacidity of the stomach
  • Back pain
  • Anxiety
  • Fullness, bloating, excessive gas or belching
  • Acne
  • Breast pain
  • Burning sensation in stomach or chest, or heartburn
  • Dryness, itching or burning sensation in the eyes
  • Changes in vision or double vision
  • Changes in perception of colors
  • Nasal congestion or a runny nose
  • Cough with mucus or phlegm
  • Cold sweats, or sudden sweating
  • Constipation
  • Tinnitus, or continuous buzzing or ringing in the ears
  • Marked reduction in desire and ability to have sex
  • Night blindness, or difficulty seeing at night
  • Difficulty moving
  • Excessive tears, or discharge, in the eyes
  • Drooping of upper eyelids
  • Dull ache, heaviness or pressure in the legs
  • Earache
  • Hearing loss
  • Sensation of self or the surroundings seem to be constantly moving
  • Feeling of warmth, or unusually cold
  • Frequent urge to defecate
  • Frozen shoulder
  • Hyperventilation
  • Erection difficulties
  • Increased appetite
  • Sensitivity to light
  • Increased sputum
  • Indigestion
  • Irritability
  • Itching of skin near damaged veins
  • Reduction or loss of strength
  • Muscle or bone pain
  • Stiffness or weakness of the muscles
  • Having nightmares or terrifying dreams, which may cause sleep disturbances
  • Noisy breathing
  • Pain or tenderness around the eyes and cheekbones
  • Problems concentrating
  • Rashes
  • Redness of skin in the face, neck and arms, and may include the upper chest
  • Redness, swelling or pain in the eye or eyelids
  • Redness, swelling or pain of the tongue or mouth
  • Restlessness
  • Sensation of spinning or vertigo
  • Sleepiness or unusual drowsiness
  • Small lumps under the skin
  • Stiff neck
  • Noticeable straining during defecation
  • Swollen feet and ankles
  • Tender or swollen glands in the neck
  • Tenderness in the stomach area
  • Tooth problems
  • Trouble swallowing
  • Uncontrollable twisting movements of the neck
  • Changes in voice
  • Unintended weight loss
  • Appearance of white patches in the mouth, tongue or throat

You can have other symptoms not listed here. If you have concerns, check with your doctor for help or first aid and if you have questions about them.

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