McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 9  Antibiotics

TABLE 9.4

DRUGS IN FOCUS Fluoroquinolones

Drug name

Dosage/route

Usual indications

Adult: 100–500 mg b.d. PO for up to 6 weeks; reduce dose in renal failure Paediatric: not recommended because of potential effects on developing cartilage Adult: 400 mg/day PO or IV for 5–10 day; reduce dose in renal impairment Adult: 400 mg PO q 12 hours for up to 28 days; reduce dose in renal impairment Adult: 1–2 gutte into affected eye every 30 mins to q 6 hours

Treatment of infections caused by a wide spectrum of gram-negative bacteria

ciprofloxacin (Ciproxin, Ciprol)

moxifloxacin (Avelox)

Treatment of adults with sinusitis, bronchitis, or community-acquired pneumonia Treatment of various urinary tract infections Treatment of corneal ulcers, bacterial conjunctivitis

norfloxacin (Noroxin, Nufloxib) ofloxacin (Ocuflox)

on the CNS membranes. GI effects include nausea, vomiting, diarrhoea and dry mouth, related to direct drug effect on the GI tract and possibly to stimulation of the chemoreceptor trigger zone (CTZ) in the CNS. Immunological effects include bone marrow depres- sion, which may be related to drug effects on the cells of the bone marrow that rapidly turn over. Other adverse effects include fever, rash and photosensitivity, a potentially serious adverse effect that can cause severe skin reactions. Advise people to avoid sun and ultra­ violet light exposure and to use protective clothing and sunscreens. Clinically important drug–drug interactions When fluoroquinolones are taken concurrently with iron salts, sucralfate, mineral supplements or antacids, the therapeutic effect of the fluoroquinolone is decreased. If this drug combination is necessary, administration of the two agents should be separated by at least 4 hours. If fluoroquinolones are taken with drugs that increase the QTc interval or cause torsades de pointes (quinidine, procainamide, amiodarone, sotalol, ery­ thromycin, pentamidine, tricyclics, phenothiazines), severe-to-fatal cardiac reactions are possible. These combinations should be avoided, but if they must be used, the person should be hospitalised with continual cardiac monitoring. Combining fluoroquinolones with theophylline leads to increased theophylline levels because the two drugs use similar metabolic pathways. The theo­ phylline dose should be decreased by half and serum theophylline levels monitored carefully. In addition, when fluoroquinolones are combined with non-steroidal anti-inflammatory drugs (NSAIDs), an increased risk of CNS stimulation is possible. If this combination is used, closely monitor the person, especially those who have a history of seizures or CNS problems.

Prototype summary: Ciprofloxacin Indications: Treatment of respiratory,

dermatological, urinary tract, ear, eye, bone and joint infections; treatment after anthrax exposure, typhoid fever. Actions: Interferes with DNA replication in susceptible gram-negative bacteria, preventing cell reproduction. Pharmacokinetics: Route Onset Peak Duration Oral Varies 60–90 minutes 4–5 hours IV 10 minutes 30 minutes 4–5 hours T 1/2 : 3.5 to 4 hours; metabolised in the liver, excreted in bile and urine. Adverse effects: Headache, dizziness, hypotension, nausea, vomiting, diarrhoea, fever, rash. ■ ■ Assess for possible contraindications or cautions : known allergy to any fluoroquinolone (obtain specific information about the nature and occurrence of allergic reactions); history of renal disease, which could interfere with excretion of the drug ; and current pregnancy or breastfeeding status because of potential adverse effects on the fetus or infant. ■ ■ Perform 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. Care considerations for people receiving fluoroquinolones Assessment: History and examination