Norbit

Indications

Disopyramide is an antiarrhythmic medicine, used to prevent and treat certain abnormal heart rhythms, mainly serious ventricular arrhythmias (fast, irregular beats starting in the lower chambers of the heart) and some atrial (upper chamber) rhythm problems. It is a specialist medicine and is usually started in hospital or under close supervision of a heart doctor.

How It Works

Disopyramide blocks sodium channels in heart muscle cells. This slows the electrical signals in the heart and makes the heart muscle less likely to fire extra beats, helping restore a steady rhythm. It also has anticholinergic effects (blocking a nerve chemical called acetylcholine), which explain side effects such as dry mouth and difficulty passing urine.

Dosage and Administration

Take exactly as prescribed by your heart doctor. Capsules or tablets are taken by mouth at regular intervals, usually divided through the day; modified-release forms are swallowed whole. The dose depends on your weight, kidney and liver function and response, and lower doses are used in older people and those with kidney problems. Injections are given only in hospital by a doctor or nurse. Do not stop suddenly without advice.

Interactions

Do not combine with other antiarrhythmics (such as Amiodarone, Flecainide, Quinidine, Sotalol) or medicines that prolong the QT interval (such as Erythromycin, Clarithromycin, some antipsychotics and antidepressants) unless a specialist advises. Beta blockers and Verapamil may weaken the heart further. Rifampicin and Phenytoin lower its levels; Clarithromycin and some antifungals raise them. Diuretics that lower potassium increase the risk of rhythm problems. It can lower blood sugar, especially with diabetes medicines.

Contraindications

Do not use if you have certain heart block or conduction problems without a pacemaker, cardiogenic shock, uncontrolled heart failure, long QT syndrome, angle-closure glaucoma, urinary retention or myasthenia gravis, or if you are allergic to Disopyramide.

Side Effects

Common side effects include dry mouth, blurred vision, constipation, difficulty passing urine, nausea, dizziness and tiredness. It can worsen heart failure, cause low blood pressure, low blood sugar or new rhythm problems.

Get urgent medical help if you faint, have a very fast, slow or irregular heartbeat, chest pain, breathlessness or swelling of the ankles, are unable to pass urine, have sudden eye pain with blurred vision, or have sweating, shaking and confusion from low blood sugar.

Pregnancy and Lactation

Use in pregnancy only if clearly needed and under specialist care, as it may trigger uterine contractions. It passes into breast milk; your doctor will decide whether breastfeeding is suitable.

Precautions and Warnings

Regular ECG, blood pressure and blood sugar checks are needed. Tell your doctor about heart failure, kidney or liver disease, enlarged prostate, glaucoma, diabetes or low potassium. Older people are more sensitive to its side effects. Dizziness or blurred vision may affect driving.

Overdose

Overdose is dangerous and can cause very low blood pressure, heart rhythm problems, breathing problems and death. Seek emergency medical help immediately.

Therapeutic Class

Class Ia antiarrhythmic agent.

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.