Overanticoagulation associated with combined use of lactulose and acenocoumarol or phenprocoumon.

Some medical textbooks on drug interactions take note of the potential interaction between laxatives and coumarin anticoagulants, but epidemiological evidence that this interaction is of practical importance is lacking. We conducted a follow-up study in a large population-based cohort to investigate which laxatives are associated with overanticoagulation during therapy with coumarins. Of the 1124 patients in the cohort, 351 developed an International Normalized Ratio > or = 6.0. The only laxative with a moderate but significantly increased relative risk of overanticoagulation was lactulose (relative risk 3.4, 95% confidence interval 2.2, 5.3). In view of the widespread use of lactulose, especially among the elderly, awareness of this potential drug interaction is required.

[1]  K. Hoffmann,et al.  Untersuchungen über die Wirkungsweise der Lactulose (β-Galactosido-Fructose) im Darm , 1964, Klinische Wochenschrift.

[2]  S. Schenker,et al.  Portal systemic encephalopathy. , 1997, Clinics in liver disease.

[3]  P. Thürmann,et al.  Clinically Important Drug Interactions with Anticoagulants , 1996, Clinical pharmacokinetics.

[4]  J. Vandenbroucke,et al.  Optimal oral anticoagulant therapy in patients with mechanical heart valves. , 1995, The New England journal of medicine.

[5]  J. Hirsh.  Oral anticoagulant drugs. , 1991, The New England journal of medicine.

[6]  L Goldman,et al.  Major bleeding in outpatients treated with warfarin: incidence and prediction by factors known at the start of outpatient therapy. , 1989, The American journal of medicine.

[7]  G. Raskob,et al.  Different intensities of oral anticoagulant therapy in the treatment of proximal-vein thrombosis. , 1982, The New England journal of medicine.

[8]  D. Hollander,et al.  Vitamin K2 colonic and ileal in vivo absorption: bile, fatty acids, and pH effects on transport. , 1977, The American journal of physiology.

[9]  D. Hollander,et al.  Vitamin K1 intestinal absorption in vivo: influence of luminal contents on transport. , 1977, The American journal of physiology.

[10]  A. Dawson,et al.  The effect of lactulose on the faecal flora of patients with hepatic encephalopathy. , 1974, Journal of medical microbiology.

[11]  D. Mossel,et al.  [STUDIES ON THE MECHANISM OF ACTION OF LACTULOSE (BETA-GALACTOSIDE ACTION OF LACTULOSE (BETA-GALACTOSIDO-FRUCTOSE) IN THE INTESTINE]. , 1964, Klinische Wochenschrift.