Prescription Drugs
Some prescription medications, even when taken as prescribed by your physician, can be dangerous. Prescription drugs cause more than 100,000 deaths in the U.S. each year. In rare cases, they may put people at risk for sudden cardiac death. Many medications have these effects, even on the healthy heart, because they: change the body's normal blood levels of potassium, sodium, magnesium and calcium. These minerals are called "ions." They are required in the proper amount to maintain normal heart function.
- affect the blood vessels or the pumping ability of the heart.
- prolong the "Q-T interval" - a measure of the time it takes to recharge the heart's pumping chambers.
- make the heartbeat too slow (bradycardia) or too fast (tachycardia).
Medications prescribed to treat abnormal heart rhythms (called "antiarrhythmic" drugs) sometimes can cause heart rhythm problems. This may be especially true of drugs that slow the heartbeat, such as flecainide and proprafenone. Anti-arrhythmic drugs should be prescribed by a doctor who is an expert in heart rhythm disorders, and the effects of the drugs used to treat them. Treatment with such drugs requires continued monitoring by physician.
Medications that affect normal levels of ions
Some medications commonly prescribed for heart disease and/or high blood pressure affect minerals in the blood needed to recharge or "repolarize" the heart after each beat. These minerals (also called "electrolytes" or "ions") are potassium, magnesium, calcium and sodium. Symptoms of excess mineral loss include:
 dizziness- rapid heartbeat
- dry mouth
- muscle pains or cramps
- too-low blood pressure
- sleepiness and confusion
Diuretics are a common type of medication that affects mineral levels. These drugs, also called "water pills," lower the blood pressure by increasing outflow of urine and reducing the amount of fluid in the body. The volume of minerals excreted from the body also increases. They also are prescribed for heart failure and other conditions that cause fluid build-up (edema).
Often, people on diuretics must take supplements to avoid depleting the body of needed minerals.
Medications that affect the blood vessels or pumping ability of the heart
 Beta-Adrenergic Blockers (Beta-blockers) are prescribed for high blood pressure or to reduce stress on the heart. They slow the heart rate, reduce the force of muscle contractions and relax the arteries. But they may cause arrhythmias in some people, especially those with a too-slow heart rate (bradycardia). They may be used to treat rapid heart rhythms (tachycardias). In rare instances, they contribute to heart failure by over-depressing the heart's ability to pump blood
.ACE inhibitors block the production of certain chemicals, especially angiotensin, which the body releases to raise blood pressure. Side effects of ACE inhibitors may include chest pain, diarrhea, fatigue, weakness and shortness of breath. They rarely cause irregular heartbeats and an increase in potassium.
Antiarrhythmic Medications
Medications used to treat arrhythmias depend on the frequency and severity of the abnormal heart rhythm, and whether it arises in the upper chambers (atria) or lower chambers (ventricles) of the heart. There is a chance that some antiarrhythmic drugs (and other types of drugs) may cause new heart rhythm problems, or make existing ones worse. Some antiarrhythmics may even cause a fatal heart rhythm disorder that leads to sudden cardiac death.
Medications that prolong the Q-T Interval
Some medications may cause Long Q-T syndrome (LQTS). This disorder affects the recharging (repolarization) of the heart after each beat. Each time the heart contracts, it sends out an electrical signal. The signal is generated by the flow of potassium, sodium, magnesium and calcium molecules through passageways in the heart called "ion channels."
If you have an arrhythmia, it is important to consult with an electrophysiologist or other physician who is an expert in heart rhythm disorders and the medications available to treat them.
 During an electrocardiography (ECG) test, the electrical signals are recorded on a printout. Each signal is represented by a line called a waveform. The letters, P, Q, R, S, and T are used to represent different parts of each waveform. The space between the beginning of the Q wave and the end of the T wave is the length of time it takes for the electrical signal to activate and inactivate the major pumping chambers of the heart (ventricles).
If there is a problem in the ion channels, the Q-T interval may be longer than normal. A prolonged Q-T interval increases the risk of a dangerous life-threatening arrhythmia called torsade de pointes. When this occurs, the heart cannot pump enough blood to the rest of the body, especially the brain. Torsade de pointes can cause fainting (syncope) and may lead to ventricular fibrillation, a deadly heart rhythm disorder that is the number one cause of sudden cardiac death.
There are nearly 50 medications that are known to prolong the Q-T interval. Generally, this is not a problem for most people and does not lead to torsades de pointes or other heart rhythm disorders. These medications should be prescribed carefully, however, for people with some types of health problems. They must be avoided altogether by people who already have been diagnosed with LQTS. If you are taking any medications that cause dizziness, fainting, confusion or irregular heart rhythms, notify your doctor immediately.
Guide to Safe Use of Medications
- Take all medications, including non-prescription drugs and supplements, with you to your doctor's appointment.
- Ask your doctor to tell you about each medication, what its side effects are. Ask how it may interact with other drugs, foods or supplements you are taking.
- Inform your physician of any side effects or allergic reactions.
- Be sure your pharmacist keeps a record of all your prescriptions. Ask for written information about their use, potential side effects and interactions with other drugs.
- Keep notes when you talk with your doctor and/or pharmacist about your medications.
- Take your medications exactly as prescribed by your doctor
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