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drug on the body (pharmacodynamics ) and the way in which the body handles the drug ( pharmacokinetics ). A drug can have many effects; therefore, the nurse must know which ones may occur when a particular drug is administered. Most of these effects are therapeutic, or helpful, whereas others can be undesirable or potentially dangerous and are known as adverse effects (see Chapter 3 for a detailed discussion of adverse effects). Sources of Drugs Drugs are available from varied sources, both natural (e.g. plants, fungi, animals or inorganic compounds) and synthetic. Plant Products Plants and plant extracts have been used as medicines for many centuries. Even today, plants are an important source of chemicals that are developed into drugs. For example, digitalis products from Digitalis purpurea (foxglove plant) used to treat cardiac disorders; opiates such as morphine, codeine and papaverine from Papaver somniferum (opium poppy); and the taxanes derived from the bark ofTaxus brevifolia (yew trees) are used in cancer chemotherapy. Plant extracts have also become the main component of the growing alternative therapy movement. Fungi The most well-known example of a drug derived from fungi is the antibiotic penicillin used to treat a number of communicable diseases. Penicillin and other -lactam antibiotics are derived from the mould Penicillium chrysogenum . The immunosuppressant drug, ciclosporin, used to reduce the activity of a patient’s immune system following organ transplantation, was also originally derived from a fungus. Animal Products Animal products are used to replace human chemicals that are not produced because of disease or genetic problems. Until 1982, insulin for treating diabetes was obtained exclusively from the pancreas of cows and pigs. Now genetic engineering , the process of altering deoxyribonucleic acid (DNA), permits scientists to produce human insulin by altering Escherichia coli bacteria, making insulin without some of the impurities that come with animal products. The insulin produced using genetic engineering procedures is known as a biopharmaceutical , a protein or nucleic acid prepared using genetic engineering technology. Inorganic Compounds Salts of various elements can have therapeutic effects in the human body. Aluminium, fl uoride, lithium, iron and even gold are used to treat various conditions. The effects of these elements were usually discovered accidentally when a cause–effect relationship was observed. Table 1.1 shows examples of some elements used for their therapeutic benefi t. Synthetic Sources Even today, many drugs are developed from chemicals in plants, animals or the environment that have been screened for signs of therapeutic activity. Most new drugs are purely synthetic. Technical advances allow scientists to alter a chemical with proven therapeutic effectiveness to make it better. Sometimes, a small change in a chemical’s structure can make that chemical more useful as a drug – more potent, more stable, less toxic. These technological advances have led to the development of groups of similar drugs, all of which are derived from an original prototype, but each of which has slightly different properties, making a particular drug more desirable in a specifi c situation. Biopharmaceuticals As mentioned above, biopharmaceuticals are proteins (including antibodies) or nucleic acids produced by genetic engineering for therapeutic purposes. There is a large range of biopharmaceuticals, including thrombolytic agents such as tissue plasminogen activator; hormones (insulin, growth hormone); vaccines; interferons used in the treatment of leukaemia and multiple sclerosis; and also monoclonal antibodies, such as trastuzumab (Herceptin), used to target specifi c proteins on cancer cells. Element Therapeutic Use Aluminium Antacid to decrease gastric acidity Management of hyperphosphataemia Prevention of the formation of phosphate urinary stones Fluoride Prevention of dental cavities Prevention of osteoporosis Gold Treatment of rheumatoid arthritis Iron Treatment of iron defi ciency anaemia Lithium Treatment of mania Table 1.1 Elements Used for Their
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