[Show abstract][Hide abstract] ABSTRACT: A 68-year-old woman was admitted to the regional hospital because of hemolytic anemia, thrombocytopenia, and neurological abnormalities including unconsciousness. One week before admission, she suffered from diarrhea and subsequently passed out and hit her face on the ground. She was suspected of having TTP and was transferred to our hospital. We performed the assays of ADAMTS13 activity and anti-ADAMTS13 antibody titers, and confirmed the diagnosis of acquired idiopathic TTP with total deficiency of ADAMTS13 activity with its inhibitor. She was initially treated with plasma exchange combined with corticosteroids, however, we were forced to substitute plasma exchange with fresh frozen plasma infusion due to procedure-associated complications. The infusion of fresh frozen plasma was known as less effective and more likely to boost inhibitor titers compared to plasma exchange. In this circumstance, we could successfully switch the plasma therapy under close monitoring of ADAMTS13 activity and anti-ADAMTS13 antibody titers which precisely revealed the disease status of TTP in our patient, and eventually she achieved complete remission with normal level of ADAMTS13 activity and no inhibitor. Our experience suggested that the measurement of ADAMTS13 activity and inhibitor titer might be valuable not only for making the diagnosis but also for guiding treatment decisions by precise evaluating of disease status in patients with the acquired form of TTP.
[Show abstract][Hide abstract] ABSTRACT: Cilostazol is an anti-platelet drug that reversibly inhibits phosphodiesterase III (PDE-III), which is ubiquitously expressed in platelets and various tissues. PDE-III converts cyclic adenosine monophosphate (cAMP) to 5'-AMP and up-regulates the intracellular concentration of cAMP, a potent inhibitor of platelet aggregation. Unlike other anti-platelet drugs, cilostazol is unique because patients receiving this drug do not have a significantly prolonged bleeding time, but the reasons for this difference are still unknown. In this study, we have examined how cilostazol inhibits platelet thrombus formation using anti-coagulated normal whole blood in which the platelets were labeled with a fluorescent dye in comparison with the anti-GPIIb/IIIa agent, tirofiban. We used an in vitro assay to examine mural platelet thrombus growth on a collagen surface under a high-shear rate flow in the absence of ADAMTS13 activity. These experimental conditions mimic the blood flow in patients with thrombotic thrombocytopenic purpura. Using this model, we clearly determined that cilostazol down-regulates the height of mural platelet thrombi formed on a collagen surface in a dose-dependent manner, without affecting the surface coverage. The concentration of cilostazol used in this study was relatively high (60-120 μM) compared to clinically relevant concentrations (1-3 μM), which may be due to the in vivo synergistic effects of PDE-III present in other tissues aside from platelets. Cilostazol does not affect the initial formation of platelet thrombi, but does inhibit the height of thrombi. These results showed a sharp contrast to tirofiban, and address why cilostazol does not significantly prolong bleeding time, despite its strong anti-platelet activity.
Full-text · Article · Jul 2012 · European journal of pharmacology