McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 9  Antibiotics

Prototype summary: Aztreonam Indications: Treatment of lower respiratory,

Prototype summary: Clindamycin Indications: Treatment of serious infections caused by susceptible strains of bacteria, including some anaerobes; useful in septicaemia and chronic bone and joint infections. Actions: Inhibits protein synthesis in susceptible bacteria, causing cell death. Pharmacokinetics: Route Onset Peak Duration Oral Varies 1–2 hours 8–12 hours IM 20–30 minutes 1–3 hours 8–12 hours IV Immediate Minutes 8–12 hours Topical Minimal absorption T 1/2 : 2 to 3 hours; metabolised in the liver, excreted in the urine and faeces. Adverse effects: Nausea, vomiting, diarrhoea, pseudomembranous colitis, bone marrow suppression, hypotension, cardiac arrest with rapid IV infusion, rash, pain on injection, abscess at injection site. Prototype summary: Erythromycin Indications: Treatment of respiratory, dermatological, urinary tract and GI infections caused by susceptible strains of bacteria. Actions: Binds to cell membranes, causing a change in protein function and cell death; can be bacteriostatic or bactericidal. Pharmacokinetics: Route Onset Peak Oral 1–2 hours 1–4 hours IV Rapid 1 hour T 1/2 : 3 to 5 hours; metabolised in the liver, excreted in bile and urine. Adverse effects: Abdominal cramping, vomiting, diarrhoea, rash, superinfection, liver toxicity, risk for pseudomembranous colitis, potential for hearing loss.

■■ The proteins or enzyme systems affected by antibiotics are more likely to be found or used in bacteria than in human cells. ■■ The primary therapeutic use of each antibiotic is determined by the bacterial species that are sensitive to that drug, the clinical condition of the person receiving the drug and the benefit-to-risk ratio for the person. ■■ The longer an antibiotic has been available, the more likely it is that mutant bacterial strains resistant to the mechanisms of antibiotic activity will have developed. ■■ The most common adverse effects of antibiotic therapy involve the GI tract (nausea, vomiting, diarrhoea, anorexia, abdominal pain) and superinfections (invasion of the body by normally occurring microorganisms that are usually kept in check by the normal flora). ■■ To prevent or contain the growing threat of drug- resistant strains of bacteria, it is very important to use antibiotics cautiously, to complete the full course of an antibiotic prescription and to avoid saving antibiotics for self-medication in the future. A person and family teaching program should address these issues, as well as the proper dosing procedure for the drug (even if the person feels better) and the importance of keeping a record of any reactions to antibiotics. dermatological, urinary tract, intra-abdominal, and gynaecological infections caused by susceptible strains of gram-negative bacteria. Actions: Interferes with bacterial cell wall synthesis, causing cell death in susceptible gram-negative bacteria; is not effective against gram-positive or anaerobic bacteria. Pharmacokinetics: Route Onset Peak Duration IM Varies 60–90 minutes 6–8 hours IV Immediate 30 minutes 6–8 hours T 1/2 : 1.5 to 2 hours; excreted unchanged in the urine. Adverse effects: Nausea, vomiting, diarrhoea, rash, superinfection, anaphylaxis, local discomfort at injection sites.

CHAPTER SUMMARY

■■ Antibiotics work by disrupting protein or enzyme systems within a bacterium, causing cell death (bactericidal) or preventing multiplication (bacteriostatic).

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