Strengths, limitations and potential bias of evidence
This systematic review to the best of our knowledge is the first of its kind to collate the evidence surrounding penicillin vs metronidazole (or broad spectrum penicillin) for the treatment of peritonsillar abscess, looking specifically at clinical response. Despite the high frequency of presentations with peritonsillar abscess, the optimum antibiotic(s) treatment of choice is still unclear and no consensus has been reached. Given this uncertainty, it is unsurprising only three studies have been found that assess the clinical effectiveness of penicillin against combination with metronidazole (or broad-spectrum counterparts), and therefore the main limitation of this review is the small amount of evidence available to present.   The potential for concerns over bias in these studies has been identified from the screening tools. Of the three randomised control trials, all were judged to have some risk of bias. The differing pencillin agents used, route, dose and frequency also limit direct extrapolation to clinical practice.
A confounding and limiting factor affecting interpretation was the use of different penicillin agent used, route, dose and frequency. Similar for metronidazole with dosages varying between 400mg TID for 7 days and 800mg BID for 10 days. These schedules will not be applicable to many current practices and understandings of the pharmacokinetics and pharmacodynamics of oral phenoxymethyl penicillin and metronidazole.