Disopyramide

Brand names

• Napamide
• Norpace
• Pisopyramide
• Rythmical
• Rythmodan

Usage

To control abnormal or irregular heart rhythms (cardiac arrhythmias).

How it works

It slows the activity of the heart's natural pacemaker and delays the transmission of electrical impulses through the heart muscle, thus stabilizing heartbeat.

Side effects

Serious

Chest pain, shortness of breath, irregular or rapid heartbeat (palpitations), fainting, sudden weight gain, swelling of fingers or ankles, anxiety. Seek medical help immediately if such symptoms arise.

Common

Dizziness, faintness, weakness caused by low blood pressure, blurred vision, constipation, dry eyes, dry nose, dry mouth, difficulty urinating. Consult your doctor if such symptoms persist.

Less common

Depression, agitation, fatigue, muscle weakness, decreased urination, nausea, vomiting, severe loss of appetite and weight, abdominal pain, yellow-tinged eyes and skin, low blood sugar causing drowsiness, headache, cold sweats, nervousness, confusion, skin rash.

Possible interactions

Other medicaments:

Disopyramide may increase the effects of:

• antihypertensive medicaments and cause excessive lowering of blood pressure.
• atropinelike medicaments.
• warfarin (Coumadin, etc.); check INR (prothrombin times) more often, and adjust dosing.

Disopyramide may decrease the effects of:

• ambenonium (Mytelase).
• neostigmine (Prostigmin).
• pyridostigmine (Mestinon).
  Benefits of these three medicaments in treating myasthenia gravis may be reduced.

Disopyramide taken concurrently with:

• amiodarone (Cordarone) may result in an abnormal heart effect.
• beta-blockers may result in abnormally low heart rates.
• cisapride (Propulsid) may lead to abnormal heart rhythm.
• digoxin (Lanoxin) can cause digoxin toxicity.
• dofetilide (Tikosyn) may lead to heart toxicity. One source suggests waiting 3 half lives (most conservative approach is 4.32 half lives) before starting a dofetilide. Do not combine.
• erythromycins (E.E.S., others) can cause increased disopyramide blood concentrations and abnormal heart effects. (Caution is advised in combining with azithromycin, clarithromycin or dirithromycin because they are structurally similar.)
• gatifloxacin (Tequin) may result in increased risk of abnormal heart rhythms.
• insulin or oral antidiabetic medicaments may result in abnormally low blood sugars.
• moxifloxacin (Avelox) may lead to abnormal heart rhythm. Do not combine.
• phenobarbital may result in loss of disopyramide's effectiveness.
• phenytoin (Dilantin) or fosphenytoin (Cerebyx) can result in decreased disopyramide effectiveness and accumulation of a metabolite of fosphenytoin or phenytoin, which may cause a severe increase in anticholinergic effects.
• potassium supplements may result in elevated potassium levels, which can lead to disopyramide toxicity.
• quinidine can cause increases in disopyramide blood levels and decreases in quinidine levels.
• quinupristin/dalfopristin (Synercid) may lead to abnormal heart rhythm. Careful patient monitoring and possible dosing decreases of disopyramide are prudent.
• ritonavir (Norvir) and perhaps other protease inhibitors may increase disopyramide blood levels and lead to toxicity.
• sparfloxacin (Zagam) may result in increased risk of abnormal heart rhythms.
• verapamil (Calan, others) can precipitate or worsen congestive heart failure.
• warfarin (Coumadin) may cause increased bleeding risk. INR must be checked more frequently.

The following medicaments may decrease the effects of disopyramide:

• all diuretics that promote potassium loss.
• rifabutin (Mycobutin).
• rifampin (Rimactane, Rifadin).

Foods:

Ask your physician regarding need for salt restriction and advisability of eating potassium-rich foods.

Herbal medicines or minerals:

Using St. John's wort, ma huang, or kola while taking this medicine may result in unacceptable heart stimulation. Belladonna, henbane, scopolia, pheasant's eye extract or lily-of-the-valley or squill powdered extracts should not be taken if you have abnormal heart rhythms. Since St. John's wort and disopyramide may increase sun sensitivity, the combination is not advised.

Alcohol:

Alcohol can increase the blood-pressure-lowering effects and the blood-sugar-lowering effects of this medicament.

Tobacco smoking:

Nicotine can irritate the heart, reducing effectiveness.

Exposure to sun:

This medicament causes photosensitization.

Exposure to heat:

The use of this medicament in hot environments may increase the risk of heatstroke.

Occurrence of unrelated illness:

Vomiting, diarrhea or dehydration can affect this medicament's action adversely. Report such developments promptly.

Discontinuation:

This medicament should not be stopped abruptly after long-term use. Ask your doctor for help regarding gradual dose reduction.

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