McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 8  Anti-infective agents

Neurotoxicity Some anti-infectives can damage or interfere with the function of nerve tissue, usually in areas where drugs tend to accumulate in high concentrations. For example, the aminoglycoside antibiotics collect in the eighth cranial nerve and can cause dizziness, vertigo and loss of hearing. Hydroxychloroquine, which is used to treat malaria and some other rheumatoid disorders, can accu- mulate in the retina and optic nerve and cause blindness. Other anti-infectives can cause dizziness, drowsiness, lethargy, changes in reflexes and even hallucinations when they irritate specific nerve tissues. Hypersensitivity reactions Allergic or hypersensitivity reactions reportedly occur with many antimicrobial agents. Most of these agents, which are protein bound for transfer through the cardiovascular system, are able to induce antibody for- mation in susceptible people. With the next exposure to the drug, immediate or delayed allergic responses may occur. In severe cases, anaphylaxis can occur, which can be life-threatening. Some of these drugs have demonstrated cross-sensitivity (e.g. penicillins, cephalo- sporins), and care must be taken to obtain a complete health history before administering one of these drugs. It is important to determine what the allergic reaction was and when the person experienced it (e.g. after first use of the drug, or after years of use). Some people report having a drug allergy, but closer investigation indicates that their reaction actually constituted an anticipated effect or a known adverse effect of the drug. Proper interpretation of this information is important to allow treatment of a person with a drug to which the person reported a supposed allergic reaction but which would be very effective against a known pathogen. Superinfections One offshoot of the use of anti-infectives, especially broad-spectrum anti-infectives, is destruction of the normal flora. Superinfections are infections that occur when opportunistic pathogens that were kept in check by the “normal” bacteria have the opportunity to invade tissues. Common superinfections include vaginal or GI yeast infections, which are associated with antibiotic therapy, and infections caused by Proteus and Pseu- domonas throughout the body, which are a result of broad-spectrum antibiotic use. If people receive drugs that are known to induce superinfections, they should be monitored closely for any signs of a new infection—sore patches in the mouth, vaginal itching, diarrhoea—and the appropriate treatment for any superinfection should be started as soon as possible.

■■ BOX 8.5  Serious adverse effects of antibiotic treatment

Gastrointestinal toxicity GI toxicity is very common with many of the anti- infectives. Many of these agents have direct toxic effects on the cells lining the GI tract, causing nausea, vomiting, stomach upset or diarrhoea, and such effects are some- times severe (see Box 8.6). There is also some evidence that the death of the microorganisms releases chemi- cals and toxins into the body, which can stimulate the chemoreceptor trigger zone (CTZ) in the medulla and induce nausea and vomiting. In addition, some anti-infectives are toxic to the liver. These drugs can cause hepatitis and even liver failure. When people are taking drugs known to be toxic to the liver (e.g. many of the cephalosporins) they should be monitored closely and the drug should be stopped at any sign of liver dysfunction. vasomotor collapse, irregular respiration and even death. In addition, the drug may cause bone marrow depression, including aplastic anaemia that can result in death. These effects are seen even with the use of the ophthalmic and otic forms of the drug. Although the use of chloramphenicol is severely limited, it has stayed on the market because it is used to treat serious infections caused by bacteria that are not sensitive to any other antibiotic. It is available in oral, IV, ophthalmic and otic forms. Chloramphenicol ( Chloromycetin ), an older antibiotic, prevents bacterial cell division in susceptible bacteria. Because of the potential toxic effects of this drug, its use is limited to serious infections for which no other antibiotic is effective. Chloramphenicol produces a “grey syndrome” in neonates and premature babies, which is characterised by abdominal distention, pallid cyanosis, Meropenem ( Merrem IV ), an IV antibiotic, inhibits the synthesis of bacterial cell walls in susceptible bacteria. It is used to treat intra-abdominal infections and some cases of meningitis caused by susceptible bacteria. Meropenem almost always causes very uncomfortable gastrointestinal effects; in fact, use of this drug has been associated with potentially fatal pseudomembranous colitis. It also results in headache, dizziness, rash and superinfections. Because of its toxic effect on gastrointestinal cells, it is used only in those infections with proven sensitivity to meropenem and reduced sensitivity to less toxic antibiotics. ■■ BOX 8.6  Severe gastrointestinal toxicity resulting from anti-infective treatment