Beta Blockers in the Treatment of Migraine
Of all the preventative medicines available across the United States, the drugs known as beta blockers are probably the most frequently prescribed. The "beta" refers to receptors on the blood vessels known as beta receptors. Beta blockers prevent the chemical interaction of certain chemicals with this receptor, hence, the term "beta blockers." Of this family of drugs, the most frequently used drug is Inderal, although others, such as Tenormin and Corgard, will also be used occasionally. Beta blockers were developed primarily for control of cardiac symptoms, but it was found coincidentally that these drugs had a remarkable effect on migraine prevention.
After this chance observation was made, studies conducted in the late 1960s and early 1970s confirmed the improvement in migraine with treatment. The studies show that sixty to seventy percent of all migraine subjects experienced a decrease of more than fifty percent in the incidence and severity of their headaches when treated with one of these beta blockers. Two beta blockers are currently FDA approved for use in the preventative treatment of migraine: propranolol (Inderal and Inderal LA) and timolol (Blocadren). Three other beta blockers are also used, although these drugs are not approved by the FDA for indication in migraine. These three agents are: atenolol (Tenormin), metoprolol (Lopressor), and nadalol (Corgard).
MECHANISM OF ACTION
The possible mechanisms of action of propranolol in the prophylactic treatment of migraine are listed below:
Inderal is prescribed in milligram dosages of 60, 80, 120, 160, and occasionally even up to 240 mg. per day. Usually, the patient will be started on a low dosage of the drug to test the patient's response. Unfortunately, many physicians will abort treatment long before they have given the drug a chance to work. Inderal may take six to twelve weeks to be effective. Not only that, but the dosage may have to be increased as the weeks go by. One of the major reasons people are failures on preventative or prophylactic drugs is that they have not taken the medication long enough, nor have they taken it in a sufficient dosage.
As with every medication, Inderal has its side effects. However, some side effects are very unique to the beta blockers. Occasionally on starting the drug, a feeling of lethargy may be experiences. After all, the role of beta blockers is to prevent the effects of "adrenaline" on the body. Sometimes there may be some overshoot effect, and the patient may feel a little tired and lethargic.
Occasionally, some may experience depression on the drug. Rarely does it ever get so severe as to necessitate stopping the medicine, but this has been reported on occasion. Another side effect which men find distressing is the appearance of impotence. Even on rare occasions, orgasmic dysfunction has been noted in women; however, fortunately these side effects are relatively rare.
If the side effects are experienced, cessation of the drug usually abolishes them. A word of caution! When stopping Inderal, it should never be discontinued immediately or sometimes there may be rebound migraine or even rebound tachycardia (speeding up of the heart rate). Inderal should be tapered over a period of weeks. Because most physicians now use the long-acting variety of Inderal, it is necessary to switch over to the short-acting medication so that the drug can be tapered when that is appropriate.
Not every patient is a candidate for Inderal. Diabetes is a contraindication because Inderal can sometimes mask the effects of hypoglycemia which is unacceptable in a diabetic patient. Similarly, patients with bronchial asthma or severe sinusitis should not be treated with this drug. Elderly patients with poor cardiac function should avoid beta blockers in general because the drug may sometimes precipitate congestive heart failure.
Many drug interactions and related problems have been reported with beta blockers. The following is a summary of some areas of special concern:
Due to their established efficacy and safety record, beta blockers play a role in the prophylaxis of migraine with and without aura. These agents have been demonstrated to reduce the frequency and intensity of migraine attacks. If patients are screened for contraindications to these medicines, then fewer side effects are reported.
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