[Initial experiences with methylene blue virus inactivated fresh frozen plasma: results of a clinical and in vitro study].

Methylene blue (MB) has recently been introduced to inactivate viruses in single donor fresh frozen plasma (FFP) units. In the first clinical study 519 units of MB-treated FFP were given to 103 patients. No specific clinical side effects with adverse reactions were recorded. However, after thawing, clots were observed in 9 of the first 110 units, although the medical staff had thawed the MB-FFP in exactly the same manner as the conventional FFP in which clots are extremely rare. The possible effects of methylene blue were investigated by subsequent in vitro experiments: Methylene blue together with light led to generation of fibrin(ogen) derivatives which have an increased tendency for aggregation but cannot be normally clotted by thrombin and even seem to interfere with normal fibrin polymerization. Inadequate conditions during plasma preparation such as long illumination or temperatures above 40 degrees C enhanced the generation of these fibrin(ogen)-derivatives. In addition, special requirements for producers and users of MB-FFP and further investigations are necessary in order to prevent complications.