Algorithm for Short-Term Prescription of Phenprocoumon

Abstract

Data from the start of anticoagulation therapy using the coumarin derivative phenprocoumon were obtained retrospectively for 101 patients, and the correct long-term maintenance dose (MD) of the drug was determined. The average loading dose was 23.2 ± 7.8 mg and the average MD 2.14 ± 0.99 mg. The physician’s prescription on discharge tended to underestimate the true MD by 0.29 ± 0.64 mg. Significant positive correlations with MD were noted for loading dose and weight and negative correlations for age, serum creatinine, initial prothrombin ratio, and length of treatment pause (days) for patients receiving an excessive loading dose. Using stepwise variance analysis, an algorithm was obtained that predicted the MD: MD = -0.7 + loading dose/10 – treatment pause/7 – age/60 + initial prothrombin ratio. The accuracy (0.02 ± 0.54 mg) was similar to that of the discharging physician. The algorithm required an average observation period of 5.4 days and the physician’s estimate 12.4 days. It is suggested that the use of the algorithm would lead to shorter hospitalization without loss of treatment accuracy.

VKORC1 and CYP2C9 Genotype Variations in Relation to Warfarin Dosing in Korean Stroke Patients

“…Age, gender, concurrent medications, and dietary vitamin K intake influence the INR level,3-7 and algorithms using these parameters have been developed 6,8. Nevertheless, these factors are insufficient to explain the wide inter-individual differences in doses required for optimal INR,9-11 which may be related to individual genetic variability 11-14.…”