one of a small group of oral anticoagulants (e.g., anisindione) designed for long-term therapeutic use in patients who cannot tolerate other oral anticoagulants. Anticoagulation using indanediones is difficult to control, and these agents may cause grave adverse effects, including severe renal and hepatic toxicity, agranulocytosis, and leukopenia. For this reason coumarin derivatives are preferred. Regular evaluations of prothrombin time are necessary. Extreme fatigue, sore throat, chills, and fever are signs of impending toxicity and require discontinuation of the drug. Compare coumarin.