From the Karen Baker, MS Pharmacology lecture I talked about last Monday...
At least once a week if not more, I have the need to prescribe antibiotics to a patient. In the past I have used amoxicillin for my patients because I thought the extended action would help treat odontogenic infections. Apparently I was mistaken in this assumption. While Amoxicillin does have a broader spectrum of action, it has poor anaerobe activity. While Penicillin VK does not have excellent anaerobic activity, it is more efficient at gram negative anaerobes. Amoxicillin does have some advantages over Penicillin VK like longer duration of activity (three times a day dosage instead of four) and more complete absorption, however these are not enough to justify the increased side effects and less efficacy.
So the ideal antibiotic treatment in patients who are not allergic to Penicillin is Penicillin VK
four times a day. 500mg is the appropriate dosage for adults. For pediatric patients, the does is 25-50 mg/kg/day. If treating an odontogenic infection and a positive response is not achieved within 48 hours, add metronidazole 4 times a day (30mg/kg/day).
Metronidazole has great effect on anaerobes, both gram negative and gram positive. After several days of infection, the majority of microbes will be anaerobic so Metronidazole helps penetrate the infection better. Just remember, always warn your patients to stay away from alcohol of all forms, including Listerine rinse for the duration of the course and 2 days after. The response can be VERY unpleasant!
Both Penicillin VK and Metronidazole are inexpensive. A five day course of Penicillin VK 500 mg costs around $13 and five days of Metronidazole 250 mg costs $15. Patients love that!