Warfarin dosage in postpartum women: a case-control study.
OBJECTIVE
To investigate the clinical suspicion that postpartum women are more difficult to anticoagulate with warfarin than non-pregnant women due to the physiological changes in coagulation proteins that persist into the postpartum period.


METHODS
A retrospective case-control study.


METHODS
University Hospital, Nottingham, UK.


METHODS
Twenty-three postpartum women discharged from the obstetric wards on warfarin and 23 age-matched control women discharged from the medical wards on warfarin were identified using hospital databases.


METHODS
Warfarin doses and international normalised ratio values were recorded from day one to 35. The number of days and total warfarin dose to achieve therapeutic international normalised ratio were recorded. Doses were compared with those recommended by a dosing nomogram.


RESULTS
The postpartum group took significantly longer and significantly larger doses of warfarin to reach therapeutic international normalised ratio (P < 0.05). The postpartum group required a persistently higher maintenance dose of warfarin. Comparing the warfarin dose given on day three with a standardised nomogram, 79% of women in the postpartum group compared with 57% in the control group were under-dosed.


CONCLUSIONS
Postpartum women require larger doses of warfarin to reach therapeutic international normalised ratio than non-pregnant women. We would recommend the use of a dosing nomogram.
Brooks
Cath
C
Department of Fetomaternal Medicine, School of Human Development, University Hospital, Queen's Medical Centre, Nottingham, UK.
Rutherford
Jane M
JM
Gould
Jane
J
Ramsay
Margaret M
MM
James
David K
DK
D000328:Adult; D000925:Anticoagulants / Q000008:administration & dosage*; D001778:Blood Coagulation Disorders / Q000188:drug therapy*; D016022:Case-Control Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D011247:Pregnancy; D011644:Puerperal Disorders / Q000188:drug therapy*; D012189:Retrospective Studies; D013997:Time Factors; D014859:Warfarin / Q000008:administration & dosage*
D000925:Anticoagulants; D014859:Warfarin