McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 9  Antibiotics

NEW CLASSES OF ANTIBIOTICS AND ADJUNCTS Research is constantly being done to develop new antibiotics to affect the emerging resistant strains of bacteria. New classes of antibiotics are daptomycin ( Cubicin ), linezolid ( Zyvox ) and tigecycline ( Tygacil ) . See the following for additional information about each of these agents. Adjuncts to antibiotic therapy include clavulanic acid and thalidomide (see Box 9.6). Daptomycin was introduced in 2003 as a cyclic lipopeptide antibiotic. This class of drug binds to bac- terial cell membranes, causing a rapid depolarisation of membrane potential. The loss of membrane potential leads to the inhibition of protein and DNA and RNA synthesis, which results in bacterial cell death. Dapto- mycin is approved for treating complicated skin and skin structure infections caused by susceptible gram-posi- tive bacteria, including MRSA . It must be given IV over 30 minutes, once each day for 7 to 14 days, which makes its use inconvenient. People should be monitored for pseudomembranous colitis and myopathies. Linezolid ( Zyvox ) was introduced in 2000. This drug is indicated specifically for treatment of infections caused by vancomycin-resistant and methicillin-resistant strains of bacteria. It is available in intravenous and oral forms. The usual adult dosage is 600 mg PO, or it may be administered IV q 12 hours for 10 to 14 days. This drug must also be used cautiously and only when a sen- sitive bacterial species has been clearly identified. It is the first oral drug approved for the treatment of diabetic foot ulcers. These drugs are part of a wide variety of compounds that are being investigated to deal with the increasing problem of resistant bacteria. Tigecycline ( Tygacil ) was the first drug of a new class of antibiotics called glycylcyclines. This antibiotic inhibits protein translation on ribosomes of certain bacteria, leading to their inability to maintain their integrity and culminating in the death of the bacterium. It is used in the treatment of complicated skin and skin structure infections and intra-abdominal infections caused by susceptible bacteria. Caution should be used with a known allergy to tetracycline antibiotics because a cross-sensitivity may occur. Women should be advised to use a barrier form of contraceptive when on this drug. People should be monitored for pseudomembra- nous colitis, rash and superinfections. Tygacil is given as 100 mg IV followed by 50 mg IV every 12 hours, infused over 30 to 60 minutes for 5 to 14 days.

■ ■ Provide the following teaching:

KEY POINTS ■■ 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. These slow-growing bacteria may need to be treated for several years before they can be eradicated. They cause tuberculosis and leprosy. ■■ Antituberculosis drugs are used in combination to increase effectiveness and decrease the emergence of resistant strains. These drugs are divided into first- line and second-line drugs. Adverse effects include rashes, an orange tint to body fluids and GI reactions. ■■ Dapsone is the only antibiotic now used on its own to treat leprosy. Thalidomide was recently reintroduced to treat an unusual reaction many people develop after being on dapsone. –– Try to drink a lot of fluids to maintain nutrition (very important) even though nausea, vomiting and diarrhoea may occur. –– Use barrier contraceptives and understand that oral contraceptives may not be effective if antimycobacterials are being used. –– Understand that normally some of these drugs impart an orange stain to body fluids. If this occurs, the fluids may stain clothing and tears may stain contact lenses. –– Report difficulty breathing, hallucinations, numbness and tingling, worsening of condition, fever and chills or changes in colour of urine or stool. Evaluation ■ ■ Monitor person’s response to the drug (resolution of mycobacterial infection). ■ ■ Monitor for adverse effects (GI effects, CNS changes and hypersensitivity reactions). ■ ■ 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