The evolution of platelet-directed pharmacotherapy

Introduction to haemostasis from a pharmacodynamic perspective

Biochemical characterization of the haemostatic system has advanced significantly in the past decades. Sub-systems, such as coagulation, fibrinolysis, blood cells and platelets and the vessel wall have been studied by specialists, mostly separately and independently. The time has come to integrate the approaches, and, in particular, to develop tests to document the state of the whole system and to have available adequate pharmacodynamic tests to evaluate treatments. Many examples are available to show that traditional general methods of clotting and lysis do not provide the information that is desired. The present tendency is to use specific methods for specific factors or effects which are very limited in pharmacological information. There is also increasing awareness of the occurrence of rather broad interindividual variability in the haemostatic system. This suggests that individually tailored treatments are required. This is the more relevant since haemostasis is a balance and treatment should be positioned between efficacy and safety. The conclusion is reached that there is a need for integrated or global methods or sets of methods that reflect the complexity and individual status appropriately and allow the practitioner to judge the effects of interventions and their individual aspects.

Advanced assessment of platelet function during adult donor care

Abnormal platelet function may complicate the assessment and treatment of continuing blood loss, hypotension, and coagulation disorders during adult donor care. Antiplatelet drugs, such as aspirin, nonsteroidal anti-inflammatory drugs, clopidogrel (Plavix), ticlopidine (Ticlid), prasugrel (Effient), abciximab (ReoPro), eptifibatide (Integrilin), and tirofiban (Aggrastat) are commonly prescribed for older patients. These medications may be part of home therapy or may be given during acute cardiac or cerebrovascular crises that may lead to brain death and organ donation. This discussion reviews normal platelet formation and function, drug actions, methods to evaluate medication effects, pharmacological characteristics, treatment recommendations for platelet transfusion, and risks attendant with those infusions.

Platelets as delivery systems for disease treatments

Platelets are small, anucleate, discoid shaped blood cells that play a fundamental role in hemostasis. Platelets contain a large number of biologically active molecules within cytoplasmic granules that are critical to normal platelet function. Because platelets circulate in blood through out the body, release biological molecules and mediators on demand and participate in hemostasis as well as many other pathophysiologic processes, targeting expression of proteins of interest to platelets and utilizing platelets as delivery systems for disease treatment would be a logical approach. This paper reviews the genetic therapy for inherited bleeding disorders utilizing platelets as delivery system, with a particular focus on platelet-derived FVIII for hemophilia A treatment.