Propranolol is in a family of pharmaceutical drugs called beta-blockers and sold under the brand name Inderal. This type of medication affects the heart and circulation system, and is used to prevent heart attacks and treat angina, or chest pain; hypertension or, high blood pressure; heart rhythm disorders; and prevent other heart and vascular, or blood vessel, conditions. According to the U.S. Food and Drug Administration (FDA), propranolol is also prescribed for muscle tremors, hyperthyroid conditions, to decrease the frequency and severity of migraine headaches, and for certain anxiety conditions.
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Beta blockers work by blocking certain sites in the central nervous system called beta-adrenergic receptor sites, as described by Drugs.com. Blocking these nerve sites decreases heart rate, blood pressure and anxiety. However, propranolol and other beta blockers can also worsen breathing disorders, such as emphysema and asthma, because they constrict the air passageways of the lungs and can cause fluid build-up in the lungs. This can result in shortness of breath, difficulty breathing and chest tightness in patients who are on propranolol for long periods of time, or who have respiratory disorders. To prevent or decrease this side effect, propranolol is prescribed in divided doses, extended-release capsules, or combined with the diuretic, hydrochlorothiazide, which causes the body to excrete fluids.
Low Blood Pressure
As propranolol and other beta blocker drugs are used to treat hypertension, or high blood pressure, and heart rate, some patients may experience fluctuating blood pressure levels or chronic low blood pressure. This can lead to symptoms such as drowsiness, tiredness, dizziness, lightheadedness, fainting and fatigue, as noted by MentalHealth.com. These side effects are more likely to occur if the patient does not take propranolol as recommended, or takes doses of the medication that are too high. These side effects may be more noticeable when getting up from a sitting or reclining position.
Decrease Diabetic Symptoms
MayoClinic.com advises that propranolol and other beta-blockers are not recommended for patients with diabetes because they may mask or cover some of the symptoms of the disease. Diabetic patients generally experience a fast or pounding heartbeat during hypoglycemia, or when the blood sugar levels fall too low. Propranolol decreases heart rate, so this symptom does not occur even with hypoglycemia. Other symptoms of hypoglycemia such as dizziness and sweating will still occur.
Other side effects of propranolol involve the digestive system. These include nausea, vomiting, stomach cramping, constipation, diarrhea, black tarry stools and abdominal pain and tenderness, as listed by MayoClinic.com. Bloating and fluid retention may also occur, and to decrease this side effect, propranolol may be combined with the diuretic, hydrochlorothiazide.