Microbiological equivalence of serum bacteriostatic and bactericidal activities of the sera from healthy volunteers receiving original meropenem (Meronem^R) and generic meropenem (Mero^R)

Background: Several generic meropenem formulations have been approved by Thai Food and Drug Administration, Ministry of Public Health since 2008. Meropenem is a parenteral drug. Therefore, a study demonstrating a biological equivalence of generic meropenem is not required for drug registration in Thailand. The objective of the study was to determine microbiological equivalence of serum bacteriostatic and bactericidal activities of the sera from healthy volunteers receiving original meropenem (Meronem^R) and generic meropenem (Mero^R). Material and Method: This was a randomized crossover study in 16 adult healthy volunteers. Each subject received one gram of Meronem^R and Mero^R in 50 ml of normal saline via intravenous infusion for 30 minutes. The blood samples were drawn at baseline prior to receiving the study drug, at 30 minutes after initiating infusion, and at 8 hours after initiating infusion. The serum bacteriostatic activity against E. coli ATCC 25922, K. pneumoniae, P. aeruginosa ATCC 27853 and A. baumannii was performed by disk diffusion The serum bactericidal activity against E. coli ATCC 25922 was performed by Serum Bactericidal Titre. Results: The average inhibition zone diameter of the serum samples from the subjects while receiving Mero^R against each tested organisms was < 1 mm smaller than that while receiving Meronem^R and such difference was not significantly different. All serum samples taken at 30 minutes after initiating Meronem^R and Mero^R had bactericidal titres against E. coli ATCC 25922 > 1:256. Only 3 serum samples taken from the subjects while receiving Mero^R at 8 hours had less bactericidal titre for 1-fold dilution when compared with that of Meronem^R. Conclusion: The sera from healthy volunteers receiving Meronem^R and Mero^R had microbiological equivalence in terms of serum bacteriostatic and bactericidal activities.