Antibiotic Use and Abuse in Dentistry

• Antibiotics can cause harm directly:

  • Fatal anaphylaxis to penicillins estimated 1:100,000
  • More of a risk with intravenous drugs than those that dentists would prescribe
  • Hypersensitivity reactions
  • Adverse drug reactions
• Antibiotics can cause harm indirectly:

  • Opportunistic infections
  • Clostridium difficile - risk of getting it about 3x greater when on antibiotics
  • Resistant organisms
  • Methicillin-resistant Staphylococcus aureus (MRSA)
  • Vancomycin-resistant Enterococcus (VRE)
  • Carbapenemase Producing Enterobacteriaceae (CPE)
  • Multi-drug resistant Mycobacterium tuberculosis (MDR-TB)
• Contra-indications to antibiotic use - reasons why we might not want to give them:

  • Absolute
  • Known hypersensitivity
  • Relative
  • Liver disease
  • Avoid tetracyclines, erythromycin and clindamycin - they're the drugs that have the highest chance of causing more liver damage
  • Reduce metronidazole dose - can't metabolise it well so it will stay in the circulation for a longer time
  • Penicillins  preferred; generally safe for patients with liver disease
• Contra-indications to antibiotic use - reasons why we might not want to give them:

  • Relative
  • Kidney disease
  • Avoid tetracyclines; they cause problems with kidney function
  • Reduce amoxicillin and erythromycin dose
  • Lymphocytic leukaemia
  • Ampicillin and amoxicillin (cause rash)
  • Glandular fever (infectious mononucleosis - Epstein-Barr Virus)
  • Ampicillin and amoxicillin (cause rash)
  • Pre-existing diarrhoea
  • Clindamycin/co-amoxiclav
  • Consider risks vs benefits of prescribing (C. diff)
• Pregnancy and lactation:

  • Teratogenic (causing malformations and birth defects) and toxic effects on developing foetus/new-born
  • Pharmacokinetic and pharmacodynamic alterations due to the changes in a woman's body during pregnancy
  • Lactation can alter drug-effectiveness
  • Breastfed infants are exposed to maternal drugs
• Only prescribe antibiotics in pregnancy if absolutely necessary. Avoid first trimester (because that's when a lot of important things for the baby are forming embryologically) and monitor breastfed new-born for GI symptoms (because may disrupt gut flora). Amoxicllin is the safest option.
• Metronidazole is generally safe in pregnancy, but less safe than amoxicillin. High doses contraindicated in pregnancy and breast-feeding. Avoid in women at risk of pre-term delivery; it can cause problems in the new-born.
• For clindamycin, caution in breastfeeding; it really knocks out the gut bacteria and causes risk of C. diff infection - so find alternative or tell mother not to breastfeed whilst taking the medication.
• Avoid co-amoxiclav if possible in pregnancy, risk of necrotising enterocolitis (enterocolitis = inflammation of the gut) in new-born.
• Avoid tetracycline in pregnancy and breastfeeding, dental discolouration (stains teeth) - causes developmental defects in new-born (neural tube defects - neural tube is where the CNS comes from, so can get problems with brain and spinal development in foetus).
• Adverse effects of antibiotics:

  • Hypersensitivity/allergy
  • Allergies to antibiotics are common
  • Allergy is mediated by antibodies (Type I-III hypersensitivity) or T-cells (Type IV)
  • Anaphylactic reactions are potentially life-threatening
  • Cross reactivity (e.g. Penicillins & cephalosporins)
• Adverse effects of antibiotics:

  • Minor adverse drug reactions
  • Gastrointestinal disturbance
  • Candidiasis - medication disrupts oral flora and makes it easier for candida to grow
• Adverse effects of antibiotics:

  • Major adverse drug reactions
  • Pseudomembranous colitis [inflammation of the large bowel - caused mainly by C. difficile infection] (especially caused by clindamycin)
  • Idiosyncratic (unexpected) liver damage (caused by Amoxicillin, Co-amoxiclav)
  • Hypokalaemia (low potassium) (caused by penicillins)
• Adverse effects of antibiotics:

  • Developmental
  • Neural tube defects (e.g. Anencephaly, spina bifida)
  • Discolouration of mineralised tissues (caused by tetracycline) [don't give tetracyclines in pregnancy because can stain teeth whilst being formed in the womb]
• Drug interactions with alcohol:

  • Metronidazole (reacts with alcohol and forms a disulfiram reaction)
  • Disulfiram is a drug that's used in the treatment of alcohol dependence
  • Alcohol is usually metabolised into acetaldehyde, which is then metabolised into acetate, which is then broken down into water & carbon dioxide
  • The enzyme that helps in this process (aldehyde dehydrogenase) is blocked by disulfiram and metronidazole though) - so acetaldehyde persists and can't be broken down, so you get nasty symptoms like nausea, vomiting and dizziness
• If you prescribe patients metronidazole, tell them not to drink.
• Anticoagulant drug interactions:

  • Metronidazole, penicillins, erythromycin: all increase effect of warfarin (because it's heavily bound to proteins - so if these drugs bind to the proteins in the blood and kick warfarin off, there'll be more active warfarin circulating and it'll have more of an anticoagulant effect), therefore greater risk of bleeding
• Antimetabolite drug interactions:

  • Penicillins and tetracyclines increase methotrexate toxicity by reducing excretion (stop body excreting methotrexate, so it persists longer in the circulation and can cause toxicity)
• Drug interactions:

  • Gout (inflammation of the joints caused by uric acid)
  • Allopurinol: rash forms when given with amoxicillin
  • Oral contraceptives
  • Effects of antibiotics on gut flora may reduce efficacy of oral contraceptives
• Uses of antibiotics in dentistry:

  • Therpeutic
  • Primary therapy
  • Adjunct therapy
  • Prophylactic (to prevent infection or to prevent complications of infection)
• Amoxicillin therapeutic use in dentistry:

  • First choice for adjunct treatment of dentoalveolar infections to limit the spread of infection
  • Prevention/treatment of infection in oro-antral communication
  • Loading dose prior to implant placement or extraction in those at risk of osteoradionecrosis or infection
• Metronidazole therapeutic use in dentistry:

  • First choice treatment in necrotising periodontal diseases and pericoronitis
  • Suitable alternative for the management of dental abscesses in pts who are penicillin allergic
  • Adjunct to the treatment of severe acute dento-alveolar infection (added to amoxicillin)
  • First choice as if pt has had recent course of penicillin
• Clindamycin therapeutic use in dentistry:

  • Second line antibiotic if pts do not respond to first line amoxicillin/metronidazole
  • First choice as loading dose prior to extraction in those at risk of osteoradionecrosis or infection, in penicillin allergy
  • Good bony penetrance
• Erythromycin therapeutic use in dentistry:

  • Alternative treatment for pts who are penicillin allergic

  BUT

  • Increased adverse effects (nausea, vomiting and diarrhoea)
  • Many organisms are resistant to erythromycin
• Therapeutic antibiotics:

  • Not an alternative to surgery/endodontics
  • Ideally should culture from a swab or aspirate
  • Identifies organisms involved
  • Indicates sensitivities
  • Normally treated empirically
  • Treat until clinical resolution
• Adjunctive therapy:

  • Mostly what we, as dentists, will use antibiotics for
  • Acute odontogenic infections
  • In addition to operative treatment
  • Periodontal conditions
  • In addition to operative treatment
• Prophylactic antibiotics:

  • Prevention of wound infection
  • Prevention of spread of infection
• Procedures where prophylactic antibiotics may increase success:

  • Tooth transplantation
  • Prevention of osteoradionecrosis
  • Advanced implantology
  • 2g amoxicillin prescribed 1 hour pre-op reduces failure rate
  • Also people who are immunosuppressed and therefore more likely to get infections post treatment
• Antibiotics are not appropriate for:

  • Inflammatory conditions
  • Early pericoronitis
  • Post-operative oedema
  • Fibrinolytic conditions
  • Alveolar osteitis (dry socket)
  • Non-bacterial infections
  • Fungal
  • Viral
• Principles of the use of antibiotics to prevent wound infection:

  • Probability of wound infection must be high
  • Within dentistry the most likely cause is decreased patient resistance
  • Immunocompromise
  • Immunosuppression
  • Previous jaw radiotherapy
  • Select the appropriate antibiotic
• Principles of the use of antibiotics to prevent wound infection:

  • Initiate therapy at correct time
  • The aim is to achieve high levels of antibiotic in the blood clot at the site of surgery
  • Therefore peak plasma levels at the end of surgery
  • Clot impenetrable to antibiotics 3 hours after formation - give around 1 hour before surgery
  • Use for appropriate length of time
• Principles of the use of antibiotics to prevent wound infection:

  1. Probability of wound infection must be high
  2. Select the appropriate antibiotic
  3. Initiate therapy at correct time
  4. Use for the appropriate length of time
• Preventing antibiotic resistance:

  • Minimise unnecessary prescribing
  • Treat the cause
  • Only give antibiotics when necessary and effective
  • Prescribe correct antibiotic for correct duration
  • Complete entire course of treatment
  • Allows for full efficacy & reduces need for repeat course