Prothrombin time , superwarfarins

Superwarfarins lower the blood concentrations of the vitamin K-dependent clotting factors II, VII, IX and X this results in prolongation of prothrombin time (PT) and partial thromboplastin time (PTT). PT and PTT should be repeated at least twice daily until a normal PT and PTT are established. Also, the blood clotting time and the bleeding time should be measured. Blood is often demonstrable in the excreta. Secondary hypochromic or microcytic anemia may be marked (Goldfrank et al, 2002 Nelson et al, 2006). 

Mullins, M.E., Brands, C.L., Daya, M.R. (2000). Unintentional pediatric superwarfarin exposures do we really need a prothrombin time Pediatrics 105(2) 402. ... 

V. Drug or laboratory interactions. Empiric use after an acute anticoagulant overdose will delay (for up to several days) the onset of elevation of prothrombin time, which may give a false impression of insignificant ingestion in a case of serious superwarfarin overdose (see p 378). 

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