McKenna's Pharmacology for Nursing, 2e

97

C H A P T E R 9  Antibiotics

KEY POINTS

KEY POINTS

■ ■ Monitor the infection site and presenting signs and symptoms (e.g. fever, lethargy) 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 decrease the development of resistant strains of bacteria. ■ ■ Monitor regularly for signs of nephrotoxicity, neurotoxicity and bone marrow suppression to effectively arrange for discontinuation of drug or decreased dose, as appropriate, if any of these toxicities occurs. Provide safety measures to protect the person if CNS effects, such as confusion, disorientation or numbness and tingling, occur. ■ ■ Provide small, frequent meals as tolerated; frequent mouth care; and ice chips or sugarless lollies to suck if stomatitis and sore mouth are problems to relieve discomfort. ■ ■ Provide adequate fluids to replace fluid lost with diarrhoea . ■ ■ Ensure that person is hydrated at all times during drug therapy to minimise renal toxicity from drug exposure. ■ ■ Instruct the person about the appropriate dosage regimen and possible adverse effects to enhance knowledge about drug therapy and to promote compliance. –– Take safety precautions, such as 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. –– Avoid exposure to other infections (e.g. crowded areas, people with known infectious diseases). –– Report difficulty breathing, severe headache, loss of hearing or ringing in the ears, or changes in urine output. Evaluation ■ ■ Monitor response to the drug (resolution of bacterial infection). ■ ■ Monitor for adverse effects (orientation and affect, hearing changes, bone marrow suppression, renal toxicity, hepatic dysfunction, GI effects). ■ ■ Evaluate effectiveness of the teaching plan (person can name drug, dosage, possible adverse effects to watch for and specific measures to help avoid adverse effects). ■ ■ Monitor effectiveness of comfort and safety measures and compliance with the therapeutic regimen. ■ ■ Provide the following teaching:

■■ Aminoglycosides inhibit protein synthesis in susceptible strains of gram-negative bacteria. ■■ These drugs are reserved for use in serious infections because of potentially serious adverse effects. Monitor for ototoxicity, renal toxicity, GI disturbances, bone marrow depression and superinfections. CARBAPENEMS The carbapenems (Table 9.2) are a relatively new class of broad-spectrum antibiotics effective against gram-positive and gram-negative bacteria. Meropenem, the first drug of the class, was discussed in Chapter 8 and has limited use because of the severe risk for poten- tially fatal GI toxicities. Newer carbapenems are not as toxic. Carbapenems discussed here include doripenem ( Doribax ), ertapenem ( Invanz ) and imipenem-cilastatin ( Primaxin ). Therapeutic actions and indications The carbapenems are bactericidal. They inhibit cell membrane synthesis in susceptible bacteria, leading to cell death (Figure 9.2). These drugs are used to treat serious infections caused by susceptible strains of Streptococcus pneumoniae , Haemophilus influenzae , Moraxella catarrhalis , Staphylococcus aureus , Strepto- coccus pyogenes , Escherichia coli , Peptostreptococcus , Klebsiella pneumoniae , Clostridium clostridioforme , Eubacterium lentum , Bacteroides fragilis , Bacteroides distasonis , Bacteroides ovatus , Bacteroides thetaio- tamicron , Bacteroides uniformis , Proteus mirabilis , Pseudomonas aeruginosa , Acinetobacter baumannii , Streptococcus agalactiae , Porphyromonas asaccharo- lytica , Prevotella bivia and other susceptible bacteria. They are indicated for treating serious intra-abdominal, urinary tract, skin and skin structure, bone and joint and gynaecological infections. See Table 9.2 for usual indications for each of these drugs. Pharmacokinetics These drugs are rapidly absorbed if given IM and reach peak levels at the end of the infusion if given IV. They are widely distributed throughout the body, although it is not known whether they cross the placenta or enter breast milk (see contraindications and cautions). Carb­ apenems are excreted unchanged in the urine and have an average half-life of 1 to 4 hours. Doripenem is given IV every 8 hours by a 1-hour IV infusion for 5 to 14 days. Ertapenem can be given IV or IM. It is given once a day for 5 to 14 days, depending on the infection.