Antibiotic prescribing
What to prescribe

Primary care dentists do not have access to microbiological sensitivity testing for infections seen in practice.

Fortunately, and despite globally increasing resistance problems, the vast majority of dental/oral infections still respond well to a wide range of antibiotics.

Historically, this has resulted in dentists having “favourites” which take little notice of antibiotic stewardship. For example, co-amoxiclav is still widely used as a first-line drug, and erythromycin for those allergic to penicillins.

When choosing an antibiotic for a dental/oral infection, the rules of antibiotic stewardship provide an order of preference for the choice.

Below is a practical list of the order in which you can consider which antibiotic to provide.

First Line

1a. Phenoxymethylpenicillin – Penicillin V / VK

The first drug to consider, it has a narrow spectrum, and is effective against most dental/oral infections. A narrow spectrum reduces the risk of creating resistance.

However, it is less reliably absorbed compared to amoxicillin, and requires compliance with a 4 times a day regime. Good compliance is an important factor in preventing resistance.

1b. Amoxicillin

When Penicillin V / VK isn’t suitable, consider amoxicillin. However, its broad spectrum can increase resistance.

Second line

When a patient is allergic to penicillins (which include amoxicillin), or has had a recent course of a penicillin, a second line drug is used.

2a. Metronidazole

Metronidazole is effective against most dental/oral infections. Its narrow spectrum reduces the chance of creating resistance. True allergy to metronidazole is very rare.

Side effects such as nausea, a metallic taste in the mouth, or gastrointestinal discomfort may prevent compliance.

Metronidazole may also cause a severe reaction with alcohol: patients who are not willing to abstain during the treatment period may not comply with the regime. Good compliance is an important factor in preventing resistance.

2b. Azithromycin

Azithromycin can be used when there is penicillin allergy and metronidazole is contra-indicated (e.g. for compliance reasons).

It has a simple once-a-day dose regime, and typically requires only a short 3-day course. Compliance is rarely a problem, and short courses create less resistance than long ones.

However, It has a broad spectrum, so that in turn increases the risk of resistance developing.

2c. Clarithromycin

Clarithromycin has a similar broad spectrum and action to azithromycin, and similar indications.

The dose regime is more complex than azithromycin, and courses are usually longer, both of which negatively affect stewardship. This normally makes Azithromycin a better choice.

2d. Erythromycin

Erythromycin has a similar broad spectrum and action to azithromycin and clarithromycin, and similar indications.

However, erythromycin is less well tolerated, poorly absorbed, and requires more frequent doses than azithromycin and clarithromycin. This normally makes Azithromycin a better choice.

Third line (not for dental primary care)

Because of multi-drug resistance, we are running out of antibiotics that will work for people with some life-threatening infections. Accordingly, certain antibiotics should now be reserved only for use following bacterial sensitivity testing, under the supervision of a consultant microbiologist or specialist in infectious diseases.

Their use is very strongly discouraged in dental primary care.

Clindamycin.

Clindamycin is a broad-spectrum antibiotic reserved for use in specific situations or when other antibiotics are contraindicated or ineffective. It can be effective against some Methicillin-Resistant Staphylococcus Aureus (MRSA) infections.

It has been associated with the development of Clostridioides difficile-associated diarrhoea (CDAD), a very serious (and sometimes fatal) condition caused by a bacterial imbalance in the intestine. This potential side effect often limits its use in unless other options are unavailable or unsuitable.

In dentistry, clindamycin is occasionally used for prophylaxis of endocarditis in susceptible patients who are allergic to amoxicillin, under the direction of the patient’s cardiologist.

Co-amoxiclav

Co-amoxiclav can be effective for infections that are resistant to amoxicillin, and to remain an effective drug (i.e. to prevent co-amoxiclav resistance), it should only be used when microbiological testing has shown this.

The 'power' of co-amoxiclav (and other third line drugs), as often promoted by Big Pharma (see image), should not be confused with an invitation to use it indiscriminately. Evidence-based decision making, rather than promotional influence, should guide antibiotic prescription. Adhering strictly to microbiological testing results ensures that we preserve the efficacy of these critical antibiotics for when they are truly needed.

Cephalosporins

Cephalosporins are a class of antibiotics structurally and pharmacologically related to penicillins. Their names usually start with cef, e.g. cefalexin, cefuroxime. They have a wide spectrum of activity.

Due to their broad-spectrum and potential for promoting resistance, they are considered third-line agents: they have no role in primary care dentistry.

Use of cephalosporins should be reserved for specific circumstances when other antibiotics are ineffective or contraindicated, under the guidance of a microbiologist or infectious disease specialist.

Tetracyclines

Tetracyclines include tetracycline, minocycline, and doxycycline, should only be used when other antibiotics are ineffective or contraindicated, under the guidance of a microbiologist or infectious disease specialist. They have no place in primary dental care.

Although sometimes used by specialist periodontists as an adjunct to Root Surface Instrumentation, systemic doxycycline and minocycline have not be shown to be clinically effective here.

Combinations

For common infections seen in primary care dentistry, combinations of antibiotics are no more effective than a single drug. If the antibiotic is not working, it should be replaced, not used in combination. Combinations increase the risk of multi-drug resistance, side effects, and complications.

One exception in dentistry is using Amoxicillin + Metronidazole in the specialist treatment of Stage III, IV periodontitis Grade C in patients aged under 45 years, as an adjunct to mechanical debridement and oral hygiene instruction in highly motivated patients. However, the benefits of a potential marginal reduction in pocket depth need to be weighed against the risks of side effects, multi-drug resistance, sensitisation etc.