McKenna's Pharmacology for Nursing, 2e

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P A R T 2  Chemotherapeutic agents

The potential for nephrotoxicity and ototoxicity with amikacin is very high, so the drug is used only as long as absolutely necessary. Adverse effects The many serious adverse effects associated with amino- glycosides limit their usefulness. The drugs come with a black box warning, alerting healthcare professionals to the serious risk of ototoxicity and nephrotoxicity. Central nervous system (CNS) effects include ototoxic- ity, possibly leading to irreversible deafness; vestibular paralysis resulting from drug effects on the auditory nerve; confusion; depression; disorientation; and numbness, tingling and weakness related to drug effects on other nerves. Renal toxicity, which may progress to renal failure, is caused by direct drug toxicity in the glomerulus, meaning that the drug molecules cause damage (e.g. obstruction) directly to the kidney. Bone marrow depres- sion may result from direct drug effects on the rapidly dividing cells in the bone marrow, leading, for example, to immune suppression and resultant superinfections. GI effects include nausea, vomiting, diarrhoea, weight loss, stomatitis and hepatic toxicity. These effects are a result of direct GI irritation, loss of bacteria of the normal flora with resultant superinfections, and toxic effects in the mucous membranes and liver as the drug is metabolised. Cardiac effects can include palpitations, hypotension and hypertension. Hypersensitivity reactions include purpura, rash, urticaria and exfoliative dermatitis. Clinically important drug–drug interactions Most aminoglycosides have a synergistic bactericidal effect when given with penicillins, cephalosporins or ticarcillin. In certain conditions, this synergism is used Prototype summary: Gentamicin Indications: Treatment of serious infections caused by susceptible bacteria. Actions: Inhibits protein synthesis in susceptible strains of gram-negative bacteria, disrupting functional integrity of the cell membrane and

therapeutically to increase the effectiveness of treat- ment. Avoid combining aminoglycosides with potent diuretics; this increases the incidence of ototoxicity, nephrotoxicity and neurotoxicity. If these antibiotics are given with anaesthetics, non-depolarising neuromuscu- lar blockers, succinylcholine or citrate anticoagulated blood, increased neuromuscular blockade with paralysis is possible. If a person who has been receiving an amino- glycoside requires surgery, indicate prominently on the person’s chart the fact that the aminoglycoside has been given. Provide extended monitoring and support after surgery.

Care considerations for people receiving aminoglycosides

Assessment: History and examination

■ ■ Assess for possible contraindications or cautions: known allergy to any aminoglycoside (obtain specific information about the nature and occurrence of allergic reactions); history of renal or hepatic disease; pre-existing hearing loss; active infection with herpes, vaccinia, varicella or fungal or mycobacterial organisms; myasthenia gravis; parkinsonism; infant botulism; and current pregnancy or breastfeeding status. ■ ■ 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. ■ ■ Perform culture and sensitivity tests at the site of infection. ■ ■ Conduct orientation and reflex assessment, as well as auditory testing, to evaluate any CNS effects of the drug . ■ ■ Assess vital signs: respiratory rate and adventitious sounds to monitor for signs of infection or hypersensitivity reactions ; temperature to assess for signs and symptoms of infection ; blood pressure to monitor for cardiovascular effects of the drug. ■ ■ Perform renal and hepatic function tests to determine baseline function of these organs and, possibly, the need to adjust dose. Implementation with rationale ■ ■ Check culture and sensitivity reports to ensure that this is the drug of choice for this person. ■ ■ Ensure that the person receives a full course of aminoglycoside as prescribed, divided around the clock, to increase effectiveness and decrease the risk for development of resistant strains of bacteria.

causing cell death. Pharmacokinetics: Route

Onset Rapid

Peak

IM, IV

30–90 minutes

T 1/2 : 2 to 3 hours; metabolised in the liver and excreted in the urine. Adverse effects: Sinusitis, dizziness, rash, fever, risk of nephrotoxicity.