Abstract: Disclosed herein is a quantitative screen for the assessment of microbiome derived drug metabolism. The disclosed quantitative screen, named MDMQ-Screen, may be employed, inter alia, for assessing the impact of the human gut microbiome on drug metabolism. MDMQ-Screen is used to measure and explain inter-individual variability in drug metabolism. This information is crucial in explaining potential toxic effects of the administered drugs, as well variability in response to therapy between individuals. Inter alia, MDMQ-Screen can be used to assess unexplained variability in drug response and toxicity of already used medications; used in future drug development pipelines to aid in the design and interpretation of clinical trials; and used at bedside to assess the probability of drug response and toxicity and provide recommendations for therapeutic modifications in a personalized medicine manner.