Dried blood spot testing for estimation of renal function and analysis of metformin and sitagliptin concentrations in diabetic patients: a cross-sectional study.

PURPOSE

Dried blot spot (DBS) analysis of drugs or clinical parameters offers many advantages. We investigated the feasibility of using DBS for analysis of anti-diabetic drugs concomitantly with the estimated creatinine clearance (Cl).

METHODS

The cross-sectional study involved physicians in an enabling analysis with 70 diabetic patients and community pharmacists in a field investigation with 84 participants. All 154 DBS samples were analyzed for creatinine, metformin, and sitagliptin.

RESULTS

The diabetic patients revealed of a wide range of age (32-88 years), BMI values (19.8-54.7 kg/m), and extent of polypharmacotherapy (1-21 drugs). A correlation factor to convert capillary blood creatinine from DBS into plasma concentrations was determined. Patients' Cl ranged from 21.6-155.9 mL/min. The results indicated statistically significant correlations (p < 0.05) between the use of two or three particular drug classes (diuretics, NSAIDs, renin-angiotensin system blockers) and a decreased renal function. DBS concentrations of metformin ranged between 0.23-4.99 μg/mL. The estimated elimination half-life (t ½) of metformin was 11.9 h in patients with a Cl higher than 60 mL/min and 18.5 h for diabetics with lower Cl. Sitagliptin capillary blood concentrations ranged between 11.12-995.6 ng/mL. Calculated t ½ of sitagliptin were 8.4 h and 13.0 h in patients with a Cl above and below 60 mL/min, respectively.

CONCLUSIONS

DBS allow for the analysis of concentrations of predominantly renally eliminated drugs and community pharmacists can provide a valuable contribution to DBS sampling.