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Metronidazole and tinnitus: A potential side effect?
I N B R I E F
Discusses clinical indications for metronidazole prescription.
Documents a case with an unusual side effect after metronidazole prescription.
Explores the literature for similar cases.
Explains how to report adverse drug reactions if they occur.
K. L. ODonnell*1 and D. Barker2
VERIFIABLE CPD PAPER
PRACTICE
As a healthcare profession, dentists have a role in ensuring the safety of prescribed medicines by reporting adverse drug reactions using the Yellow Card Scheme. This article briey describes a case where metronidazole, an antibiotic commonly prescribed by dentists, may have caused ototoxicity and explores the evidence around this. It also highlights the method for reporting such effects.
INTRODUCTION
Metronidazole is a synthetic nitroimidazole based on a natural antiparasitic substance derived from a Streptomyces species in 1955.It was rst approved for management of bacterial infections in 1981.It is active only against bacteria that are obligate anaerobes and acts by entering the cell causing DNA damage that leads to cell death.1 Currently in the UK, metronidazole is used for treatment of anaerobic bacterial infections, protozoal infections, Helicobacter pylori eradication, stulating Crohns disease and topically for skin conditions.2 Metronidazole accounted for 2.0% of antibiotics dispensed in Scotland in 2012.3 In England in 2011, 1,919,600 prescriptions for metronidazole were dispensed by community pharmacies.4
Metronidazole is widely prescribed in dentistry as many intra-oral infections are assumed to have a predominantly anaerobic ora. In England in 2011, 1,089,447 dental prescriptions for metronidazole were dispensed by community pharmacies.5 Dental prescriptions therefore represented 56.8% of total metronidazole prescriptions dispensed in England in 2011.4,5 Metronidazole is most commonly recommended in the following situations:61. In patients with a dental abscess with spreading infection or systemic
involvement who are allergic to penicillin. Or as an additional drug to penicillin in this situation in a non-allergic patient2. In patients with pericoronitis or acute necrotising ulcerative gingivitis that has failed to respond to local measures.
Some evidence indicates that metronidazole can be a useful addition to non-surgical management in carefully selected patients with chronic and aggressive periodontitis. This antibiotic has been shown in systematic reviews to signicantly decrease probing depths, decrease bleeding on probing and increase clinical attachment loss gain when compared to non-surgical management alone.7-9 However, it must be...