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P A R T 2  Chemotherapeutic agents

avium-intracellulare , which causes mycobacterium avium complex (MAC), is seen in people with AIDS or in other people who are severely immunocompro- mised. Rifabutin ( Mycobutin ), which was developed as an antituberculosis drug, is most effective against M. avium-intracellulare. A ntituberculosis drugs Tuberculosis can lead to serious damage in the lungs, the GU tract, bones and the meninges. Because M. tubercu- losis is so slow growing, the treatment must be continued for 6 months to 2 years. Using the drugs in combination helps to decrease the emergence of resistant strains and to affect the bacteria at various phases during their long and slow life cycle (Table 9.8). First-line drugs for treating tuberculosis are used in combinations of two or more agents until bacterial conversion occurs or maximum improvement is seen. The first-line drugs for treating tuberculosis are isoni- azid (generic), rifampicin ( Rifadin ), and ethambutol ( Myambutol ). If the person cannot take one or more of the first-line drugs, or if the disease continues to progress because of the emergence of a resistant strain, second-line drugs can be used. The second-line drugs include rifabutin ( Mycobutin ). In addition, drugs from other antibiotic classes have been found to be effective in second-line treat- ment, such as ciprofloxacin ( Ciloxan , Ciprol ) which is a fluoroquinolone. L eprostatic drugs The main antibiotic used to treat leprosy is dapsone (generic), which has been the mainstay of leprosy treat- ment for many years, although resistant strains are emerging (Table 9.8) so other drugs such as clofazimine ( Lamprene ) are also used. Similar to the sulfonamides, dapsone inhibits folate synthesis in susceptible bacteria. In addition to its use in leprosy, dapsone is used to treat Pneumocystis carinii pneumonia in people with AIDS and for a variety of infections caused by susceptible bacteria, as well as for bites by the brown recluse spider (rarely found in Australia). Clofazimine is used to treat multibacillary forms of leprosy but only in combination with dapsone or rifampicin. Recently, the hypnotic drug thalidomide ( Thalomid ) has also been used in erythema nodosum leprosum that occurs after treatment for leprosy (Box 9.6). Therapeutic actions and indications Most of the antimycobacterial agents act on the DNA and/or RNA of the bacteria, leading to a lack of growth and eventually to bacterial death (see Figure 9.2).

KEY POINTS ■■ Tetracyclines inhibit protein synthesis and prevent bacteria from multiplying. ■■ Tetracyclines can cause damage to developing teeth and bones and should not be used with pregnant women or children. ■■ Monitor the person for GI effects, bone marrow depression, rash and superinfections. Caution women that tetracyclines may make oral contraceptives ineffective. ANTIMYCOBACTERIALS Mycobacteria—the group of bacteria that contain the pathogens that cause tuberculosis and leprosy—are clas- sified on the basis of their ability to hold a stain even in the presence of a “destaining” agent such as acid. Because of this property, they are called “acid-fast” bacteria. The mycobacteria have an outer coat of mycolic acid that protects them from many disinfectants and allows them to survive for long periods in the environment. It may be necessary to treat these slow-growing bacteria for several years before they can be eradicated. Mycobacteria cause serious infectious diseases. The bacterium Mycobacterium tuberculosis causes tubercu- losis, the leading cause of death from infectious disease in the world. For several years the disease was thought to be under control, but with the increasing number of people with compromised immune systems and the emergence of resistant bacterial strains, tuberculosis is once again on the rise. Mycobacterium leprae causes leprosy, also known as Hansen disease, which is characterised by disfigur- ing skin lesions and destructive effects on the respiratory tract. Leprosy is also a worldwide health problem; it is infectious when the mycobacteria invade the skin or res- piratory tract of susceptible individuals. Mycobacterium diarrhoea, cramps or changes in colour of urine or stool. Evaluation ■ ■ Monitor the person’s response to the drug (resolution of bacterial infection). ■ ■ Monitor for adverse effects (GI effects, rash and superinfections). ■ ■ Evaluate the effectiveness of the teaching plan (person can name the drug, dosage, possible adverse effects to expect and specific measures to help avoid adverse effects). ■ ■ Monitor the effectiveness of comfort and safety measures and compliance with the regimen. KEY POINTS