The influence of age on the response to anticoagulants.

1 A group of 114 patients on long-term anticoagulant therapy was studied. The daily maintenance dose of both phenprocoumon, bishydroxycoumarin and warfarin was found to be significantly lower in patients aged between 61 and 70 years than in the those between 50 and 60 years of age. The mean daily dose of bishydroxycoumarin, hower, when expressed on a weight basis, was not significantly lower in the elderly. 2 For bishydroxycoumarin but not for phenprocoumon and warfarin there was found a statistically significant correlation between the daily maintenance dose and the weight of the patient. 3 The mean daily dose of both bishydroxycoumarin and warfarin was 30-40% lower than that recommended in the literature. 4 'Correction' was made for potential drug interference by excluding patients in continuous medication with order drugs known to influence the treatment with orally administered anticoagulants. The interindividual variation in dosage requirements of coumarin drug was thereby reduced in the age groups above 60 years. 5 The level of vitamin-k dependent coagulation factors, measured by Owren's 'P and P' method (PP%) was significantly lower (P less than 0.001) in patients of advanced age (between 61 and 70 years) than in younger patients (between 50 and 60 years). 6 The plasma concentration of albumin was significantly lower in patients over 60 years than in those under that age. 7 Correlation (P less than 0.01) was found between the daily maintenance dose of phenprocoumon and the plasma concentraction of albumin.