Meds and you

27 September 2013

Isosorbide dinitrate

Isosorbide dinitrate is a nitrate vasodilator. Nitrate vasodilators are drugs that widen and relax blood vessels to reduce the workload on the heart.


Isosorbide dinitrate is the active ingredient of Dinospray buccal spray (Nappi code: 701500-001), Isordil tablets (Nappi code: 734381-018, 026; 734403-003), Isordil sublingual tablets (Nappi code: 734411-006); Isordil tebmids SA tablets (Nappi code: 734438-001, 028), Sandoz Isosorbide Dinitrate sublingual tablets (Nappi code: 784192-006), Sandoz Isosorbide dinitrate tablets (Nappi code: 784206-009, 784214-018).

General information
Isosorbide dinitrate is a nitrate vasodilator. Nitrate vasodilators are drugs that widen and relax blood vessels to reduce the workload on the heart, and thereby also improve the supply of oxygen- rich blood to the heart.

In South Africa isosorbide dinitrate is registered for the treatment and prevention of angina, a suffocating chest pain which results when partially clogged arteries restrict the flow of oxygen-rich blood to the heart; and chronic heart failure, a condition where the heart can no longer pump enough blood to the body.

If you develop chest pain during exercise, taking these tablets before exercise will increase the amount of exercise you can do before chest pain begins.

Isosorbide dinitrate does not cure any of these conditions, but merely keeps its symptoms under control. For this drug to be effective, it has to be taken regularly.

The first few doses of this drug may cause dizziness if you get up suddenly from sitting or lying down. It is advised to get up carefully until you know how this drug affects you.

Treatment should not be stopped abruptly, especially if you have been taking this drug for a prolonged period of time. To prevent the return of symptoms you should decrease your dose gradually only as directed by your doctor.

How does isosorbide dinitrate work?
Vasodilators relax smooth muscle within blood vessels via a direct effect it has on these arterial muscles. As a result it widens and relaxes blood vessels to reduce the workload on the heart, and to increase the supply of oxygen-rich blood to the heart. This leads to chest pain subsiding.

Fast facts

Drug schedule: schedule 3
Available as: isosorbide dinitrate is available as tablets, sublingual tablets, oral spray and as injection.
What does it do? Isosorbide dinitrate widens blood vessels to reduce chest pain.
Overdose risk: medium
Dependence risk: low
Is isosorbide dinitrate available as a generic? yes
Is isosorbide dinitrate available on prescription only? yes

User information

Onset of effect: depends on formulation. Sublingual tablets and oral spray may take effect within a few minutes; normal tablets may take up to 30 minutes to start working
Duration of action: depends on formulation. Sublingual tablets and oral spray may have an effect for up to two hours, while the duration of action of tablets are 5 - 8 hours
Dietary advice: take tablets with water 1 hour prior to a meal, or 2 hours after a meal.
Stopping this medicine: do not stop using this medication abruptly, as it may cause a recurrence of the original symptoms being treated. It is advised that you decrease your dose gradually as directed by your doctor.
Prolonged use: some patients may develop a tolerance to the effect of isosorbide dinitrate, which causes its effects to be reduced over time. Speak to your doctor if you suspect your treatment to be losing it efficacy.

Special precautions
Consult your doctor before using this drug if:

  • you have anaemia
  • you have glaucoma
  • you have history of a head injury
  • you have history of heart attach
  • you have low blood pressure
  • you have an underactive thyroid

Pregnancy: avoid. Potential risk to the foetus has been reported. Consult your doctor before use, or if you are planning to fall pregnant.
Breastfeeding: avoid. It is unknown how this medication may affect your baby. Consult your doctor before use.
Porphyria: avoid. This medication may cause serious adverse effects. Consult your doctor before use.
Infants and children: this medication is not intended for use in children.
The elderly: no special precautions need to be taken.
Driving and hazardous work: caution is advised as use of this medication may lead to dizziness, light-headedness and/or sedation. Avoid such activities until you know how this medication affects you.
Alcohol: avoid concomitant use of alcohol with this medication.

Possible side effects

Side Effect
Consult your doctor

Only if severe
In all cases








heart rhythm disturbances


skin rash


eye pain




Drug interactions

alcohol reduced blood pressure - risk of dizziness and fainting
medication for high blood pressure reduced blood pressure - risk of dizziness and fainting
heparin blood-clotting effect of heparin is reduced
sildenafil causes life-threatening lowering of blood pressure and should be avoided at all times when taking nitrates
sumatriptan possible vasospasm of coronary arteries which may worsen angina

Overdose action
A small overdose is no cause for concern. In case of intentional large overdose, seek emergency medical attention.

Recommended dosage
Adults, angina. Sublingual: 2.5 - 15mg daily in divided doses 2 - 3 hours apart; oral: 10 - 20 mg 6 - 8 hourly.

This material is not intended to substitute medical advice, but is for informational purposes only. Please consult a physician for specific treatment and recommendations.


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