title: Tolerability and pharmacokinetics of metformin and the dipeptidyl peptidase-4 inhibitor sitagliptin when co-administered in patients with type 2 diabetes.
abstract: OBJECTIVE
  As part of the clinical development of sitagliptin, a dipeptidyl peptidase-4 inhibitor, for the treatment of type 2 diabetes, the potential for pharmacokinetic interactions with other antihyperglycemic agents used in managing patients with type 2 diabetes are being carefully evaluated. The purposes of this study were to evaluate the tolerability of co-administered sitagliptin and metformin and effects of sitagliptin on metformin pharmacokinetics as well as metformin on sitagliptin pharmacokinetics under steady-state conditions.
  
  
  METHODS
  This placebo-controlled, multiple-dose, crossover study in patients with type 2 diabetes assessed the tolerability of co-administered sitagliptin (50 mg b.i.d.) with metformin (1000 mg b.i.d.). Patients received, in a randomized crossover manner, three treatments (each of 7 days duration): 50 mg sitagliptin twice daily and placebo to metformin twice daily; 1000 mg of metformin twice daily and placebo to sitagliptin twice daily; concomitant administration of 50 mg of sitagliptin twice daily and 1000 mg of metformin twice daily. Following dosing on Day 7 of each treatment period, these pharmacokinetic parameters were determined for plasma sitagliptin and metformin: area under the plasma concentrations-time curve over the dosing interval (AUC(0-12h)), maximum observed plasma concentrations (C(max)), and time of occurrence of maximum observed plasma concentrations (T(max)). Renal clearance was also determined for sitagliptin.
  
  
  RESULTS
  In this study, no adverse experiences were reported by 11 of 13 patients. Two patients had adverse experiences, which were not related to study drugs as determined by the investigators. The mean metformin plasma concentration-time profiles were nearly identical with or without sitagliptin co-administration [metformin AUC(0-12h) geometric mean ratio (GMR; [metformin + sitagliptin]/metformin)] was 1.02 (90% CI 0.95, 1.09). Similarly metformin administration did not alter the plasma sitagliptin pharmacokinetics [sitagliptin AUC(0-12 h) GMR ([sitagliptin + metformin]/sitagliptin)] was 1.02 (90% CI 0.97, 1.08) or renal clearance of sitagliptin. No efficacy measurements (glycosylated hemoglobin or fasting plasma glucose) were obtained during this study. Urinary pharmacokinetics for metformin were not determined due to the lack of effect of sitagliptin on plasma metformin pharmacokinetics.
  
  
  CONCLUSIONS
  In this study, co-administration of sitagliptin and metformin was generally well tolerated in patients with type 2 diabetes and did not meaningfully alter the steady-state pharmacokinetics of either agent.
authors.affiliation: Merck Research Laboratories, Rahway, NJ 07065-0900, USA. gary_herman@merck.com
authors.forename: Gary A
authors.initials: GA
authors.lastname: Herman
authors.forename: Arthur
authors.initials: A
authors.lastname: Bergman
authors.forename: Bingming
authors.initials: B
authors.lastname: Yi
authors.forename: Mark
authors.initials: M
authors.lastname: Kipnes
mesh_terms: D058892:Adenosine Deaminase Inhibitors; D000328:Adult; D019540:Area Under Curve; D018592:Cross-Over Studies; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D018819:Dipeptidyl Peptidase 4; D004311:Double-Blind Method; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D005260:Female; D052216:Glucagon-Like Peptide 1; D006023:Glycoproteins / Q000037:antagonists & inhibitors; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D008687:Metformin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008875:Middle Aged; D011719:Pyrazines / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000068900:Sitagliptin Phosphate; D014230:Triazoles / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D058892:Adenosine Deaminase Inhibitors; D006023:Glycoproteins; D007004:Hypoglycemic Agents; D011719:Pyrazines; D014230:Triazoles; D052216:Glucagon-Like Peptide 1; D008687:Metformin; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4; D000068900:Sitagliptin Phosphate