Isobide MR

Isobide MR - Precautions | Dosage | Side Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on Fri, 17 Apr 2020. To read more about an author, click here.

Isobide MR is a medicine manufactured by Arrow Pharma Pty Ltd in Cremorne, Australia. It contains an active substance called isosorbide mononitrate and belongs to a group of anti-anginal drugs - medicines used to prevent angina.

Angina is one of the leading causes of death worldwide, and is caused by insufficient blood supply to the myocardium (heart muscle).

TGA states that this medicine should not be used to treat an acute attack of angina but only to prevent it.

Mechanism of Action

Studies show that certain chemical derivatives of isosorbide mononitrate act by relaxing the smooth muscle of blood vessels, including the blood vessels of the heart. Relaxation of the muscles of the blood vessels leads to dilation (widening) of the blood vessels, thus facilitating the flow of blood and oxygen to the heart muscle, thus solving the cause of the angina.

This drug is thought to have another positive therapeutic effect, namely inhibition of platelet aggregation, that is, prevention of platelet adhesion. Preventing platelet aggregation also prevents the formation of thrombi that can cause a heart attack, stroke or other disorders.

The mechanism of Isobide MR's action is complex, but it comes down to the release of nitrite oxide, which further induces stimulation of an enzyme called guanylate cyclase. This enzyme then triggers a series of biochemical reactions, which ultimately lead to vasodilation - dilation of blood vessels.

Contraindications

Isobide MR is contraindicated in patients taking medications used in erectile dysfunction therapy, such as:

  • Sildenafil, known as Viagra
  • Tadalafil, known as Cialis
  • Vardenafil, know as Levitra, and others

Concomitant use with these drugs can cause severe hypotension (low blood pressure), which can further cause heart attack.

Isobide MR is also contraindicated in patients who are hypersensitive (allergic) to isosorbide mononitrate, isosorbide dinitrate, nitroglycerin and other organic nitrates.

Precautions

Because Isobide MR leads to vasodilation, this drug very often causes headaches, which can be mild to moderate. The FDA recommends paracetamol or acetylsalicylic acid (Aspirin) to treat Isobide MR-induced headaches.

If you have severe headaches, consult your doctor. Never change the dosage regimen just to avoid headaches. Changing the dosage regimen can cause serious complications.

As there are insufficient studies on the use of this medicine in children, its use is not recommended in children.

There are no pharmacokinetic studies on the use of isosorbide mononitrate modified-release tablets in patients with impaired renal function. The half-life of the drug is thought to be longer in patients with severe renal impairment, which may complicate the treatment. Therefore, extra precaution is advised if Isobide MR is used in patients who have kidney problems.

Caution is advised if Isobide MR is used in patients who have liver problems (such as cirrhosis), as this medicine affects portal pressure.

Dosage Instructions

Isobide MR is available as 60 mg modified-release tablets. The usual dose is 60 mg once a day, but your doctor may increase your dose to 120 mg once a day.

As stated by the manufacturer of this drug, taking doses higher than 120 mg or taking this drug more frequently (more frequently than once a day), can cause tolerance to anti-anginal effects. Tolerance to anti-anginal effects may lead to decreased drug efficacy in angina pectoris treatment, which can cause serious complications.

Your doctor will explain how to use this medicine. Strictly follow the instructions given by your doctor.

Swallow the tablet whole with one glass of water. Taking Isobide MR with food does not change its efficacy, so you can take the tablet with or without food.

Abrupt withdrawal is not recommended as it might cause side effects. Therefore, a gradual dose reduction is recommended before Isobide MR is discontinued.

Use of Isobide MR During Pregnancy and Breastfeeding

Isobide MR (isosorbide mononitrate), belongs to pregnancy category B. Studies on animals with high doses of this drug have shown that it does not exhibit fetotoxic effects. However, some studies on animals have shown that Isobide MR can reduce fetal weight and increase the incidence of stillbirth.

There are no adequate studies on humans, so caution should be exercised when this drug is administered during pregnancy.

It is recommended to avoid breastfeeding while taking this medicine.

Interactions

Isobide MR should not be used concomitantly with the following medicines, because concomitant administration may result in extremely low blood pressure:

  • Medicines used to treat erectile dysfunction, such as: tadalafil, vardenafil, sildenafil, and avanafil
  • Riociguat - a drug used in the treatment of chronic, thromboembolic pulmonary hypertension
  • Tizanidine - a medicine used to treat muscle spasms
  • Prilocaine - a local anesthetic

Concomitant use of Isobide MR with calcium blockers (such as nifedipine, verapamil, nicardipine, and diltiazem) is not recommended because there is a greater risk of orthostatic hypotension (low blood pressure occurring when you stand up from sitting or lying position).

Inform your doctor about any medicines you are using.

Side Effects

Isobide MR can cause the following side effects:

  • Headache
  • Low blood pressure
  • Dizziness
  • Nausea
  • Vomiting
  • Diarrhea
  • Cough
  • Chest pain
  • Diarrhea
  • Emotional lability
  • Abdominal pain
  • Fatigue
  • Hypersensitivity

Tell your doctor if you are experiencing any side effects.

References

  1. TGA
  2. Torfgard KE, Ahlner J. Mechanisms of action of nitrates. Cardiovasc Drugs Ther. 1994. 8(5): 701-17.
  3. Arrow Pharma Website

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.