Dental antibiotics – When to use what

Dental antibiotics – When to use what

Cephalosporins don’t offer any advantage over penicillin V unless the patient is in the hospital. Cephalosporins are effective against S aureus, an organism responsible for many secondary infections that patients acquire in hospitals. For penicillin-allergic patients, the antibiotic of choice is clindamycin. If allergic to both then see below.  Macrolides, such as erythromycin and azithromycin, have no place in the treatment of odontogenic infections and have the potential to cause significant harm. Tetracyclines, although effective for the treatment of some periodontal infections, are not indicated in the treatment of patients with infections of odontogenic origin.

If the source of the infection has been removed and the patient fails to respond favorably after two to three days of penicillin V or clindamycin therapy, it is necessary to add metronidazole. Metronidazole is highly effective against anaerobic bacteria but inactive against obligate aerobes, thus it is a good antibiotic for sinus graft infections. Therefore, it is not appropriate as a first line of defense or replacement antibiotic for infections of odontogenic origin, but is very effective in combination with the primary antibiotic of choice.

The recommended dental antibiotic dosages are as follows:

  • Penicillin V: 100mg loading and then 500mg QID 3-7 days. This is our first line of defense.
  • Amoxicillin: 1000mg loading and then 500mg TID for 3-7 days.
  • Clindamycin: 600mg loading dose and then 300mg TID or QID for 3-7 days. This is first line if allergic to pen VK.
  • Metronidazole: 1000mg loading dose and then 500mg TID for 5-7 days. This is adjunct to pen VK or clindamycin if no improvement after 2-3 days, both will be taken then.

What to do when a patient is allergic to both penicillin and clindamycin?

When patient is allergic to both penicillin and clindamycin then probably best to have them ask MD.  Dentaltown thread on this.  Great study on allergy to antibiotics.

  • Azithromycin Z-Pack 3 or 5 day pack (This is arguably number 2 after amoxicillin for endodontic infection according to AAE guideline below)
  • Clarithromycin 500mg loading dose and then 250mg q 12hr 7-14 day
  • Erythromycin 500 mg (2 tabs for premed) 250-500mg q6-12hr 7 day. AAE states this should be thought of as historical antibiotic and is not useful for odontogenic infections. Fall 2019 update.

Penicillin allergy chart = very useful!

Should patients take the full does of antibiotics?

The dosage and time lines are arbitrary and best guesses more than anything that comes from solid research. Add in the fact that every infection and individual is different and that the bacteria is mutating means IMHO the guidelines are not terribly useful. The AAE put out a very nice dental antibiotics myths. I especially like the following two myths,

  • Myth #7: Antibiotic dosages, dosing intervals and duration of therapy are established for most infections.
  • Myth #8: Bacterial infections require a “complete course” of antibiotic therapy.

Another article from Discover Oct 2014 issue that lists plenty of research showing that it is likely NOT the best advice to take all antibiotics.

When should a patient take an antibiotic for a root canal?

Patients should not be given antibiotics for a root canal treatment unless there are signs of systemic infection, which are fever, malaise, cellulitis and/or lymphadenopathy. Pen VK and amoxicillin are fist line defense for endodontics, although amoxicillin is preferable. Dosage for amoxicillin is same as above for just 2-3 days. If this does not improve symptoms after the root canal then go to Augmentin (125mg clavulanic acid per dose). If penicillin allergy then clindamycin.

What if a patient is already taking an antibiotic and requires a prophylactic antibiotic?

“Another concern that dentists have expressed involves patients who require prophylaxis but are already taking antibiotics for another condition. In these cases, the recommendations for infective endocarditis recommend that the dentist select an antibiotic from a different class than the one the patient is already taking. For example, if the patient is taking amoxicillin, the dentist should select clindamycin, azithromycin or clarithromycin for prophylaxis.”   From this post on antibiotic prophylaxis recommendations.

Issues with antibiotic resistance and overuse

We need to ensure we are not over-prescribing antibiotics. There are at least 2 million antibiotic resistant infections in the US a year and 23,000 deaths. JOE Spet 2017 AAE Guidance

C. difficile

Without question we are causing some of these Clostridium difficile infections from the overuse of antibiotics. The antibiotic most commonly to get blamed for this is Clindamycin, but amoxicillin and cephalosporins are responsible as well. Nearly 500,000 C. difficile infections occur a year n the US and 29,000 people die from it. Anyone taking Clindamycin needs to stop if they have diarrhea with fever, abdominal pain, or mucus or blood in the stool.

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