Purpose: To compare the stability of the effect of two oral anticoagulants, one of them (acenocoumarol) with a short half life and the other one with a long half life (warfarin) in patients in the stable phase of treatment (at least 2 months with treatment before entering the study).
Patients and methods: During a year period (January-December 1993) a comparative study of two groups of 53 patients each was performed: group 1 patients were treated with warfarin and group 2 with acenocoumarol. Both groups were paired with respect to age, sex, diagnosis for anticoagulant therapy and desired therapeutic range (INR 3-4.5). The mean value of controls per patient, the dosage changes, the evolutive controls and the incidence of haemorrhagic and thromboembolic episodes were studied.
Results: The controls performed in group 1 were 728 in total with a mean value of 13.74 per patient and 800 in group 2 with a mean value of 15.09 per patient. A change in the dosage was performed in 214 controls in patients of group 1 and in 269 of group 2. Seventeen patients had 38 haemorrhagic episodes (2 major and 36 minor) in group 1, and 6 of group 2 had 20 episodes (2 major and 18 minor). Significant differences were observed in the mean value of controls (p = 0.04), the evolutive controls (p < 0.001), the global incidence of haemorrhages (p = 0.008) and incidence of minor ones (p = 0.006). No significant differences in dosage were observed. In both groups no thromboembolic episodes during the period of study were reported.
Conclusions: Anticoagulant treatment with warfarin is more stable than with acenocoumarol. The total controls and the mean value of controls per patient are decreased. Nevertheless with warfarin we have observed a greater incidence of haemorrhagic episodes.