McKenna's Pharmacology for Nursing, 2e

105

C H A P T E R 9  Antibiotics

Pharmacokinetics Aztreonam is available for IV and IM use only and reaches peak effect levels in 1 to 1.5 hours. Its half-life is 1.5 to 2 hours. The drug is excreted unchanged in the urine. It crosses the placenta and enters breast milk (see contraindications and cautions). Contraindications and cautions Aztreonam is contraindicated with any known allergy to aztreonam. Use with caution in people with a history of acute allergic reaction to penicillins or cephalosporins because of the possibility of cross-reactivity ; in those with renal or hepatic dysfunction that could interfere with the clearance and excretion of the drug ; and in pregnant and breastfeeding women because of potential adverse effects on the fetus or neonate. Adverse effects The adverse effects associated with the use of aztreonam are relatively mild. Local GI effects include nausea, GI upset, vomiting and diarrhoea. Hepatic enzyme eleva- tions related to direct drug effects on the liver may also occur. Other effects include inflammation, phlebitis and discomfort at injection sites, as well as the potential for allergic response, including anaphylaxis. precautions : known allergy to lincosamides, macrolides and monobactams (obtain specific information about the nature and occurrence of allergic reactions); history of liver disease that could interfere with metabolism of the drug ; and current pregnancy or breastfeeding status because of potential adverse effects on the fetus or infant. ■ ■ Perform a physical assessment to establish baseline data for assessing the effectiveness of the drug and the occurrence of any adverse effects associated with drug therapy. ■ ■ Examine the skin for any rash or lesions to provide a baseline for possible adverse effects. ■ ■ Obtain specimens for culture and sensitivity testing from the site of infection. ■ ■ Conduct assessment of orientation, affect and reflexes to establish a baseline for any CNS effects of the drug. ■ ■ Assess liver and renal function test values to determine the status of renal and liver functioning and to determine any needed alteration in dosage. ■ ■ Monitor temperature to detect infection. Care considerations for people receiving macrolides, lincosamides or monobactams Assessment: History and examination ■ ■ Assess for possible contraindications or

■ ■ Obtain baseline electrocardiogram to rule out conditions that could put the person at risk for serious arrhythmias. Implementation with rationale ■ ■ Check culture and sensitivity reports to ensure that this is the drug of choice for this person. ■ ■ Monitor hepatic and renal function test values before therapy begins to arrange to reduce dose as needed. ■ ■ Ensure that the person receives the full course of the medication as prescribed to eradicate the infection and to help prevent the emergence of resistant strains. ■ ■ Ensure that the person swallows the tablet whole; it should not be cut, crushed or chewed, to ensure therapeutic dose of the drug. ■ ■ Monitor the site of infection and presenting signs and symptoms (e.g. fever, lethargy, urinary tract signs and symptoms) throughout the course of drug therapy. Failure of these signs and symptoms to resolve may indicate the need to reculture the site. Arrange to continue drug therapy for at least 2 days after all signs and symptoms resolve, to help prevent the development of resistant strains. ■ ■ Provide small, frequent meals as tolerated to ensure adequate nutrition with GI upset ; frequent mouth care and ice chips or sugarless lollies to suck to provide relief of discomfort if dry mouth is a problem ; and adequate fluids to replace fluid lost with diarrhoea. ■ ■ Ensure ready access to bathroom facilities to assist people with problems associated with diarrhoea. ■ ■ Institute safety measures to protect person from injury if CNS effects occur. ■ ■ Arrange for appropriate treatment of superinfections as needed to decrease the severity of infection and complications. ■ ■ Instruct the person about the appropriate dosage regimen and possible adverse effects to enhance knowledge about drug therapy and to promote compliance. For the monobactam agent aztreonam: this drug can be given only IV or IM, so the person will not be responsible for administering the drug. ■ ■ For lincosamides, take additional precautions that include careful monitoring of GI activity and fluid balance and stopping the drug at the first sign of severe or bloody diarrhoea. –– Take safety precautions, including changing position slowly and avoiding driving and hazardous tasks, if CNS effects occur. –– Try to drink a lot of fluids and to maintain nutrition (very important) even though nausea, vomiting and diarrhoea may occur. ■ ■ Provide the following teaching: