Can be intentional (e.g. suicide attempt) or accidental (ingestion by child, or mistaking different coloured tablets). Often iatrogenic due to misjudged dosage, inadequate monitoring, or failure to appreciate interactions with other drugs.
Can be rapidly reversed with FFP or a combination of factor concentrates, sometimes termed prothrombin complex concentrate. The latter contains clotting factors in the right proportion to reverse warfarin. Commercial products include human-derived products such as Beriplex™ and Octaplex™. The effect, however, is relatively short-lived effect as the half-life of many of these factors is in the order of several hours. More lasting reversal requires vitamin K, but this can take 8-12 hours to become effective.