Main groups of drugs

For those people who do need drugs, however, there is a vast array to choose from.

One group already mentioned is the chemotherapeutic agents that are used to treat bacterial or related infections without being unduly toxic to the patient. These include sulphonamides, which are useful in treating urinary tract infections, and antibiotics, which are used to treat a whole host of bacterial infections that cause serious disorders such as septicaemia, pneumonia, syphilis, meningitis and many more. Penicillin and tetracycline are examples of antibiotics. There are also some chemotherapeutic drugs that are not sulphonamides or antibiotics. Another class of drugs includes those that act on the gastrointestinal tract. Antacids are used to reduce gastric acidity and bring relief to people suffering from gastritis, heartburn, dyspepsia and peptic ulcers by neutralizing gastric acid. Spasmolytics, often added to antacids, reduce spasms and motility in the stomach, thus relieving pain and extending the activity of the antacid by delaying emptying of the stomach. Antiemetics are used to prevent vomiting and nausea, particularly when vomiting serves no useful purpose. A laxative may be used to stimulate peristalsis and promote bowel evacuation. Drugs that promote excretion of urine by the kidneys v are called diuretics. They are used to prevent water retention, improve the function of vital organs and increase the action of antihypertensive drugs. One of the largest and most important group of drugs includes those that depress part of the central nervous system. These include anaesthetics, antidepressants, anticonvulsants (used in the treatment of epilepsy), sedatives (which reduce mental activity), hypnotics (which induce sleep), tranquillizers (to treat anxiety, tension, and some forms of mental illness), narcotics (potent pain-killers that may induce sleep and also dependence) and analgesics (which relieve pain without sedation).

To treat inflammatory rheumatoid disorders, non-steroidal anti-inflammatory drugs (NSAIDs) are used. They are thought to inhibit the synthesis of chemicals called prostaglandins, which are involved in inflammation.

The group of drugs that act on the autonomic, or involuntary, nervous system, which controls the activities of the gastrointestinal tract, the heart and vascular system, eyes and secretory glands, may be used to depress or stimulate a part of the system. For example, adrenaline is used to stimulate the sympathetic nervous system, resulting in constriction or dilation of certain blood vessels, and is used to stop internal bleeding and to re-start the heart. If the heart is failing, one of the group of cardiovascular drugs may be needed. For example, digoxin produces more powerful and effective heart contractions, but slows the heart rate. ‘Beta-blockers’ prevent the access of catecholamines (naturally-produced adrenaline and noradrenaline) to cardiac beta receptor sites and inhibit their action. They also reduce the contractile force of heart muscle, which is useful in conditions where the blood supply to the heart is restricted. Beta-blockers are used in conditions such as angina and hypertension.

Hormones are also important to the efficient running of our bodies. These are chemical substances released into the bloodstream by endocrine glands. Hormones extracted from glands or made synthetically can help us when glands fail or when they are needed in greater concentration than the body can produce – for example, cortisone to treat inflammations, and insulin to treat diabetes.

To treat allergic conditions, in which the release of histamines gives rise to hay fever and asthma, antihistamines are used to block the access of histamine to receptor sites.

It is not possible here to include details of all the other groups of drugs, which include drugs to treat cancers, skin disorders, the respiratory system and the genitourinary system. More drugs are being developed all the time, many directed towards the treatment of cancer. Interferon, a naturally produced substance, has been shown to have strong anti-cancer properties, but is not yet in clinical use.