McKenna's Pharmacology for Nursing, 2e

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P A R T 2  Chemotherapeutic agents

is little cross-resistance with other forms of antibiotics. However, misuse of these drugs in the short time the class has been available has led to the existence of resistant strains of bacteria (see contraindications and cautions). The fluoroquinolones are indicated for treating infections caused by susceptible strains of gram-negative bacteria, including E. coli , P. mirabilis , K. pneumoniae , Enterobacter cloacae , Proteus vulgaris , Proteus rettgeri , Morganella morganii , Moraxella catarrhalis , H. influ- enzae , H. parainfluenzae , P. aeruginosa , Citrobacter freundii , S. aureus , Staphylococcus epidermidis , some Neisseria gonorrhoeae and group D streptococci. These infections frequently include urinary tract, respiratory tract and skin infections. Ciprofloxacin is effective against a wide spectrum of gram-negative bacteria. In 2001, it was approved for prevention of anthrax infec- tion in areas that might be exposed to germ warfare. It is also effective against typhoid fever. See Table 9.4 for usual indications for each of these agents. Pharmacokinetics The fluoroquinolones are absorbed from the GI tract, metabolised in the liver and excreted in the urine and faeces. These drugs are widely distributed in the body and cross the placenta and enter breast milk (see contra­ indications and cautions). Ciprofloxacin is available in injectable, oral and topical forms. Moxifloxacin is available in oral and IV forms. Norfloxacin is only available in an oral form. Ofloxacin is available as an ophthalmic agent for the treatment of ocular infections caused by susceptible bacteria. Contraindications and cautions Fluoroquinolones are contraindicated in people with known allergy to any fluoroquinolone and in pregnant or breastfeeding women because potential effects on the fetus and infant are not known. Use with caution in the presence of renal dysfunction, which could inter- fere with the metabolism and excretion of the drug , and seizures, which could be exacerbated by the drugs’ effects on cell membrane channels. Because so many resistant strains are emerging, always perform culture and sensitivity tests of infected tissue to determine the exact bacterial cause and sensi- tivity. These drugs have been associated with lesions in developing cartilage and therefore are not recommended for use in children younger than 18 years of age. Adverse effects These drugs are associated with relatively mild adverse reactions. The most common are headache, dizziness, insomnia and depression related to possible effects

KEY POINTS ■■ Lincosamides are similar to macrolides but are more toxic. They are used to treat severe infections. Monitor the person for pseudomembranous colitis, bone marrow depression, pain and CNS effects. ■■ Macrolides are in a class of older antibiotics that can be bactericidal or bacteriostatic. They are used to treat URTIs and UTIs, and are often used when people are allergic to penicillin. Monitor the person for nausea, vomiting, diarrhoea, dizziness and other CNS effects. ■■ The monobactam antibiotic aztreonam is effective against only gram-negative enterobacteria; it is safely used when people are allergic to penicillin or cephalosporins. Monitor the person taking aztreonam for GI problems, liver toxicity and pain at the injection site. FLUOROQUINOLONES The fluoroquinolones (Table 9.4) are a relatively new synthetic class of antibiotics with a broad spectrum of activity. Fluoroquinolones include ciprofloxa- cin ( Ciproxin, Ciprol ), which is the most widely used fluoroquinolone; moxifloxacin ( Avelox ), norfloxacin ( Noroxin, Nufloxib ) and ofloxacin ( Ocuflox ). Therapeutic actions and indications The fluoroquinolones enter the bacterial cell by passive diffusion through channels in the cell membrane. Once inside, they interfere with the action of DNA enzymes necessary for the growth and reproduction of the bacteria (see Figure 9.1). This leads to cell death because the bacterial DNA is damaged and the cell cannot be maintained. The fluoroquinolones have the advantage of a unique way of disrupting bacterial activity. There –– Report difficulty breathing, severe headache, severe diarrhoea, severe skin rash, and mouth or vaginal sores. Evaluation ■ ■ Monitor person’s response to the drug (resolution of bacterial infection). ■ ■ Monitor for adverse effects (orientation and affect, GI effects, 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