Dosing of dabigatran etexilate in relation to renal function and drug interactions at a tertiary hospital

BACKGROUND: Plasma concentrations of the anticoagulant dabigatran are correlated with clinical outcomes, and are affected by renal function, intestinal P-glycoprotein (P-gp) activity and stomach acidity. AIMS: To determine the adherence to dabigatran etexilate renal dosing guidelines, the frequency of co-prescription of potentially interacting drugs in patients on dabigatran, and how these related to dabigatran dosing. METHODS: A retrospective chart review of 204 patients discharged from a tertiary hospital on dabigatran etexilate over a 12-month period. Creatinine clearance, using the Cockcroft-Gault equation, was used as the surrogate of renal function in the 86 patients where this was calculable. RESULTS: Prescribed dabigatran etexilate dose rates in relation to creatinine clearance and the manufacturer's guidelines were classified as 'standard', 'low' and 'high' in 47% (40/86), 49% (42/86) and 5% (4/86) of patients respectively. Co-prescribed drugs that potentially interact with dabigatran etexilate were present in 75% (154/204) of patients and included strong P-gp inhibitors (16%, 32/204), proton-pump inhibitors (46%, 94/204) and anti-platelet drugs (47%, 95/204). Co-prescription of strong P-gp inhibitors was associated with the prescription of 'low' dose rates relative to renal function (P = 0.025). CONCLUSIONS: Few patients were dosed excessively in relation to creatinine clearance. Around 50% was prescribed with 'low' dose rates in relation to creatinine clearance, which because of the association with co-prescription of strong P-gp inhibitors may be clinically appropriate. Most patients were co-prescribed with drugs that potentially interact with dabigatran etexilate.