Propranolol drug. Polarised light micrograph of crystals of the beta-blocker drug Propranolol (Propranolol hydrochloride). This drug, a beta- adrenoceptor blocking drug (or beta-blocker) is used to lower blood pressure, correct abnormal heart rhythm (arrhythmia) and to treat angina. It is also used in patients who develop heart symptoms in response to stress or tension. Beta- blocker drugs selectively block receptors of the sympathetic nervous system in heart muscle, in the process decreasing the activity of the heart. Propranolol may also be used to treat overactive thyroid gland, and to prevent attacks of migraine. Magnification: x10 at 35mm size.