ANTITHYROID AGENTS

ANTITHYROID AGENTS are used in the treatment of overactivity of the thyroid gland — hyperthyroidism. thyrotoxicosis or Graves’ disease. In thyrotoxicosis there is excess secretion of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3; liothyronine). This excess results in an exaggerated version of the normal activity of the gland, so that there are the symptoms of increased metabolic rate, an increase in body temperature, sweating, increased sensitivity to heat, nervousness, tremor, raised heart rate, tendency to fatigue and sometimes loss of body weight with an increased appetite. The cause of thyrotoxicosis may be simple overactivity of the gland; or toxic nodular goitre where there is secretion from a benign tumour or a carcinoma of the thyroid; or diffuse toxic goitre (Graves’ disease; exothalmic goitre) in which there are additional symptoms, including a swelling of the neck (goitre) due to enlargement of the gland, and protrusion of the eyes (exothalmos). How the disease is treated depends on its origin, but one final therapy is surgical removal of part of the gland or, more commonly, treatment of the gland with radioactive iodine to reduce the number of cells. For this purpose 131I is given orally Read more […]

β-ADRENOCEPTOR ANTAGONISTS

β-ADRENOCEPTOR ANTAGONISTS (also known as β-adrenergic receptor blocking drugs, β-adrenoceptor blocking drugs or beta-blockers) are drugs that inhibit certain actions of the sympathetic nervous system by blocking the action of adrenaline and noradrenaline (catecholamine mediators acting predominantly as hormone or neurotransmitter respectively). Among other actions, β-adrenoceptors have cardiac stimulant actions, they dilate certain blood vessels, suppress motility within the gastrointestinal tract, stimulate certain aspects of metabolism causing an increase in glucose and free fatty acids in the blood. These actions, in concert with those of the α-adrenoceptors, help prepare the body for emergency action. However, in disease, some of these effects may be inappropriate, exaggerated and detrimental to health, so β-blockers may be used to restore the balance. Thus β-blockers are used to lower blood pressure when it is abnormally raised in cardiovascular disease (see ANTIHYPERTENSIVE AGENTS): to correct certain heartbeat irregularities and tachycardias (see ANTIARRHYTHMICS); to prevent the pain of angina pectoris during exercise by limiting cardiac stimulation (see ANTIANGINALS)’, to treat myocardial infarction, Read more […]

ANTIHYPERTENSIVE AGENTS

ANTIHYPERTENSIVE AGENTS are used to reduce high blood pressure when it is raised in disease, though such drugs are not necessarily hypotensive (i.e. they may not lower blood pressure in normotensive subjects). Hypertension is an elevation of arterial blood pressure above the normal range expected in a particular age group, sex etc. It can have several different causes, which to some extent determine the treatment. Above certain values, after making lifestyle corrections, intervention with drug therapy may reduce the risk of heart attacks, kidney failure or a stroke, and may help in the treatment of angina pectoris. There are several large groups of drugs used as antihypertensives, each with a specific mode of action. DIURETICS are in common use as antihypertensives, and often a mild diuretic may be all that is required: e.g. amiloride. chtorothiazide, ethacrynic acid, frusemide, hydrochlorothiazide, spironolactone, triamterene. Beta-blockers, of which there are many, may be used if further treatment is necessary, with or without simultaneous administration of a diuretic: e.g. acebutolol, oxprenolol, propranolol and sotalol. See β-ADRENOCEPTOR ANTAGONISTS. Other antihypertensive drugs work as antisympathetic Read more […]

ANTIARRHYTHMIC AGENTS

ANTIARRHYTHMIC AGENTS (antidysrhythmic agents) are used to treat a number of heart conditions characterized by irregularities of heart beat. They have been classified under the Vaughan Williams Scheme, though not all clinically used agents neatly fit these classes. Class I (which has a number of subtypes) is mainly used to treat atrial and ventricular tachycardias, and contains a number of SODIUM-CHANNEL BLOCKERS, e.g. disopyramide, flecainide, lignocaine, procainamide and quinidine. Class II, which is valuable for stress-induced tachycardias, contains β-ADRENOCEPTOR ANTAGONISTS, e.g. metoprolol, propranolol. Class III, which is used for certain tachycardia syndromes, includes amiodarone (whose mechanism of action is not clear), POTASSIUM-CHANNEL BLOCKERS and the atypical β-blocker sotalol. Class IV is used for atrial tachyarrhythmias and contains certain CALCIUM-CHANNEL BLOCKERS, e.g. diltiazem and verapamil. In addition to drugs in these classes, others may be used for certain arrhythmias. Digoxin may be used for treatment of atrial fibrillation, adrenaline for asystolic cardiac arrest, atropine for sinus bradycardia, methacholine (rarely) for supraventricular tachycardia, magnesium salts for ventricular Read more […]

ANTIANGINAL AGENTS

ANTIANGINAL AGENTS are used to relieve angina pectoris, an intense pain due to cardiac ischaemia, which is especially pronounced in exercise angina. The disease state often results from atheroma; a degeneration of the lining of the arteries of the heart due to build-up of fatty deposits. The objective is to relieve the heart of work, and to prevent spasm or to dilate coronary arteries. Unloading can be achieved by stopping exercise, preventing the speeding of the heart and by dilating the coronary arteries. Beta-blockers, by inhibiting the effect of adrenaline and noradrenaline on the heart, prevent the normal increase in heart rate, and are very effective in preventing exercise angina. Examples of beta-blockers used for this purpose include acebutolol, atenolol, metoprolol, nadolol, oxprenolol, pindolol, propranolol, sotalol and timolol. See β-ADRENOCEPTOR ANTAGONISTS. Many VASODILATORS act directly to relax vascular smooth muscle, so dilating blood vessels and thereby increasing blood flow (see SMOOTH MUSCLE RELAXANTS). For the acute treatment of anginal pain (and to a lesser extent in preventing angina attacks) the nitrates are widely used, e.g. glyceryl trinitrate, isosorbide dinitrate, isosorbide mononitrate Read more […]