Inter- and Intra-individual Variations in Metformin Pharmacokinetics - The Importance of Genes and Drug Interactions

The investigators aim to investigate the interindividual variation in metformin AUC in a large cohort of healthy volunteers after a single dose of metformin. Part 1 is driven by the hypothesis that metformin AUC and renal clearance exhibit significant interindividual variation. However this has never been documented in a large cohort of healthy volunteers. The investigators aim to investigate the potential interaction between codeine and metformin in the intestine. The hypothesis underlying part 3 is that the increased risk of early discontinuation of metformin during co-administration with codeine is primarily due to local inhibition of OCT1 via codeine at the intestinal level.