Objective: To provide a comprehensive review of warfarin use in infants and children, including recommendations for appropriate dosage and monitoring parameters.
Data sources: A MEDLINE search (1966-1995) was used to identify pertinent English-language articles in the medical literature. The key search term was warfarin. Additional material was obtained from references cited in articles retrieved through MEDLINE.
Study selection: All articles involving children younger than 18 years were evaluated. In addition, articles on the pharmacokinetics and pharmacodynamics in adults, adverse effects, and drug interactions were included.
Data extraction: Material selected for review included clinical trials, case reports, and surveys of practice.
Data synthesis: Warfarin has been used as prophylactic therapy in children with prosthetic cardiac valves as well as for prevention of thromboembolic complications associated with autoimmune disorders and protein C or protein S deficiency. Warfarin also has been used to prevent embolization in children with deep-vein thrombosis or clots in central venous catheters. According to the literature, an initial dosage of 0.1 mg/kg/d should provide anticoagulation without significant adverse effects. As in adults, dosing should be adjusted to achieve a target international normalized ratio (INR). Although the target range in children is not well established, INR values of 1.5-3 are recommended for most patients. Higher values have been used in children with prosthetic cardiac valves and hereditary clotting disorders.
Conclusions: Due to its infrequent use, there is limited information on the effects of warfarin in children. Basic guidelines for initiating and monitoring warfarin were developed by using data gathered from clinical trials, retrospective reviews, case series, and surveys of practice.