We commend Crowther and colleagues1 on their comparison of 2 different loading doses of warfarin sodium, particularly given the wide variation of practices that exist. However, we question whether any concrete conclusions can be reached from the results. The major problem is in assuming that the study groups are equal in regard to characteristics.
It is well known that liver function, nutritional status, and certain foods and medications can all have major effects on the pharmacokinetics and pharmacodynamics of warfarin.2,3 It seems imperative, therefore, that Crowther and colleagues include information regarding these factors in their article, especially given the small number of subjects in the trial. Without this information, there is concern that the 2 groups could have been different, invalidating the results.
Angelo S, Nardino RJ. Comparing 5-mg and 10-mg Warfarin Loading Doses: Are the Groups Similar?. Arch Intern Med. 1999;159(14):1624. doi: