G Nifedipine

Indications

Nifedipine is used to treat high blood pressure (hypertension) and to prevent chest pain (angina). Doctors also use it for Raynaud's phenomenon, where fingers and toes turn white and painful in the cold, and in some other conditions as prescribed.

How It Works

It is a calcium channel blocker. It relaxes the muscles in the walls of the arteries so they widen. This lowers blood pressure and improves blood flow to the heart muscle.

Dosage and Administration

• Modified-release twice-daily tablets: usually 10 to 20 mg twice a day, up to 40 mg twice a day if the doctor advises.
• Once-daily long-acting tablets: usually 20 to 30 mg once a day, increased by the doctor if needed (up to 90 mg a day).
• Short-acting capsules and other uses: as prescribed only.

Swallow modified-release tablets whole; do not crush or chew them. Take at the same time each day. Avoid grapefruit and grapefruit juice.

Interactions

Grapefruit juice, Erythromycin, Clarithromycin, Ketoconazole, Itraconazole and some HIV medicines can raise its level. Rifampicin, Phenytoin, Carbamazepine and Phenobarbital can greatly reduce its effect; do not take it with Rifampicin. Other blood pressure medicines and alcohol add to the lowering of blood pressure. It may raise the level of Digoxin.

Contraindications

• Allergy to nifedipine or similar medicines.
• Cardiogenic shock, very low blood pressure, or severe narrowing of the aortic valve.
• Unstable angina, or within one month of a heart attack.
• Use with Rifampicin.

Side Effects

Common: headache, flushing, feeling warm, dizziness, swelling of the ankles, fast heartbeat and tiredness, often in the first weeks. Others: constipation, nausea and swollen gums with long-term use.

Get urgent medical help if chest pain gets worse or starts soon after a dose, you faint, you have a very fast or irregular heartbeat, yellow skin or eyes, or signs of an allergic reaction such as swelling of the face or difficulty breathing.

Pregnancy and Lactation

Doctors sometimes use nifedipine to treat high blood pressure in pregnancy, but it should be used only if prescribed for this purpose. Small amounts pass into breast milk; it is often considered acceptable while breastfeeding, but ask your doctor first.

Precautions and Warnings

Do not stop suddenly unless the doctor advises. Stand up slowly. Use with caution in heart failure, low blood pressure, liver disease and diabetes. Some long-acting tablets leave an empty shell in the stool, which is normal. Older people may need a lower dose.

Overdose

Too much can cause severe low blood pressure, dizziness, fainting, slow or fast heartbeat and high blood sugar. Seek emergency medical help.

Therapeutic Class

Calcium channel blocker (dihydropyridine).

Storage

Store below 30°C in a dry place, protected from light (keep tablets in the original pack), and out of the reach of children.