Antibiotic combination therapy against resistant bacterial infections: synergy, rejuvenation and resistance reduction.

Introduction: Anti-Microbial Resistance (AMR) is a pandemic which threatens modern medicine. There is a lack of effective drug treatment due to the slow pace, high cost and low achievable sales prices of new antibiotic monotherapies. New hope comes in the shape of antibiotic combination therapy, which although used by mother nature, is under-explored and could provide the solution to AMR.Areas covered: We performed a search of Pubmed and Medline using the keywords 'combination therapy', 'antimicrobial resistance' for articles between 1930 and 2019, as supplemented with other relevant references to our knowledge. We have reviewed the theoretical considerations for combination development and examine the existing and future clinical indications of combination therapies. We have discussed the potential of antibiotic combinations to provide therapeutic synergy, rejuvenating the effectiveness of old antibiotics to which the bacteria had developed resistance previously. We have examined the current thinking and evidence on resistance reduction using combination therapies, with a review on toxicity and drug-drug antagonism.Expert opinion: Antibiotic combination therapy, exploiting synergies, old-drug rejuvenation and resistance reduction could provide the solution to AMR. The number of pharmaceutical companies in this area is likely to expand, bringing promising combinations to the bedside, to save millions of lives worldwide.