The panel agreed that resource requirements associated with administering oral vitamin K are likely to be moderate owing to the high cost of pharmaceutical-grade phytonadione (vitamin K) in the United States. The feasibility of using over-the-counter (OTC) sources of vitamin K may be constrained by the variable quality and actual 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: ANTICOAGULATION MANAGEMENT 3277 active-ingredient content of available OTC vitamin K formulations (available OTC tablet strengths would require the administration of many tablets to achieve recommended doses, and there have been reports that some OTC brands contain less or more actual vitamin K than advertised on the product label).181 Conclusions and research needs for this recommendation. Based on the low quality of the available evidence, the guideline panel remained uncertain regarding the net benefit associated with administration of oral vitamin K in addition to withholding VKA doses for patients presenting with INRs between 4.5 and 10.0 (or the upper limit of the laboratory readout). Given the high cost of prescription oral vitamin K tablets in the United States and the variable vitamin K content of available OTC products, the panel conditionally recom- mends against administering oral vitamin K. Administration of oral vitamin K might be considered for patients at high risk of developing bleeding complications (eg, those who have undergone recent surgical procedures) or in situations where the INR is expected to be prolonged for a longer period of time (eg, intentional overdose, presence of interacting drugs, or very low weekly VKA dose requirement). Data for VKAs other than warfarin are limited, reducing confidence in this recommendation for patients treated with phenprocoumon, which has a longer half-life than warfarin. The panel identified the following additional research questions. 