Glyocard

Indications

Glyceryl trinitrate (also called nitroglycerin) is used to:

• Relieve an angina attack (chest pain caused by reduced blood flow to the heart), and prevent angina before activities known to bring it on.
• Prevent angina over the long term (sustained-release tablets and skin patches).
• Treat acute heart failure, very high blood pressure during surgery and some heart attacks (injection, in hospital).
• Relieve pain and help healing of anal fissures (a small tear in the skin of the anus), as an ointment.

How It Works

It releases nitric oxide in the body, which relaxes and widens blood vessels. This reduces the work the heart has to do and improves blood flow to the heart muscle, easing chest pain.

Dosage and Administration

• Angina attack, spray under the tongue (400 mcg per spray): sit down, then spray 1 or 2 puffs under the tongue and close the mouth. Do not inhale the spray. If the pain has not eased after 5 minutes, take another dose. If the pain is still there 5 minutes after the second dose, call an ambulance or go to the nearest emergency department at once.
• Tablets under the tongue (usually 300 to 500 mcg): sit down and let 1 tablet dissolve under the tongue; follow the same 5-minute rule as above.
• Before exercise or another known trigger: 1 dose a few minutes beforehand.
• Sustained-release tablets and skin patches: as prescribed; swallow tablets whole. A daily nitrate-free period (for example, removing a patch overnight) is usually advised so the medicine keeps working.
• Ointment for anal fissure: as prescribed, usually a small amount to the anal area twice a day.
• Injection: given in hospital by a doctor or nurse.

Interactions

• Sildenafil, Tadalafil, Vardenafil and Avanafil (for erectile dysfunction or pulmonary hypertension) and Riociguat: must never be taken with glyceryl trinitrate, as blood pressure can fall dangerously low.
• Other medicines that lower blood pressure, such as beta-blockers, calcium channel blockers, diuretics, ACE inhibitors, some antidepressants and antipsychotics, and alcohol: increase the risk of dizziness and fainting.
• Heparin: its effect may be reduced when glyceryl trinitrate is given by drip.

Contraindications

• Allergy to nitrates.
• Very low blood pressure, shock or fainting due to low blood pressure.
• Use with phosphodiesterase-5 inhibitors (such as Sildenafil) or Riociguat.
• Certain heart conditions: hypertrophic obstructive cardiomyopathy, severe narrowing of the aortic or mitral valve, constrictive pericarditis or cardiac tamponade.
• Raised pressure inside the head, including after a head injury or brain bleed.
• Severe anaemia.

Side Effects

Headache is very common, especially at first, and usually eases with continued use. Other effects include flushing, dizziness or lightheadedness when standing up, a fast or pounding heartbeat, nausea and weakness. Patches and ointment may irritate the skin. Get urgent medical help if chest pain does not go away after two doses, five minutes apart; if you faint or nearly faint; if you have a very slow heartbeat; or if you notice signs of a severe allergic reaction.

Pregnancy and Lactation

Use during pregnancy and breastfeeding only if the doctor considers it necessary. Ask your doctor before use.

Precautions and Warnings

Always sit or lie down when using it for an angina attack, as it can cause sudden dizziness. Avoid alcohol. Tell your doctor if you have low blood pressure, glaucoma, thyroid, liver or kidney disease, or recent heart attack. Your body can get used to nitrates if they are taken continuously, so follow the dosing plan your doctor gives. Do not stop long-term nitrates suddenly. Remove patches before an MRI scan or the use of a defibrillator. Carry your quick-relief spray or tablets with you at all times and check the expiry date.

Overdose

Overdose can cause severe headache, very low blood pressure, fainting, a fast heartbeat, flushing, vomiting and, rarely, a blood problem that causes bluish skin (methaemoglobinaemia). Lie down with the legs raised and seek emergency medical help.

Therapeutic Class

Nitrate vasodilator; antianginal medicine.

Storage

Store below 30°C, away from light and out of the reach of children. Keep tablets in their original tightly closed container, as they lose strength when exposed to air, heat or moisture. The spray is flammable: keep it away from heat and flames, and do not pierce or burn the container, even when empty.