Effect of aspirin on complement in vivo.

Following ingestion of aspirin (1 g) complement consumption could be demonstrated in 18/20 healthy volunteers. A slight to moderate decrease of whole complement activity (CH50) and of the components C1, C4 and C2 was found. In addition, reduced levels of the C1 inactivator (C1 IA) were measured in 19/20 probands. The drop in C titers and C1 IA was only detectable within a short period of time and 30 min after ingestion of the drug the titers were usually returning to normal. In view of these findings, the possible role of complement in adverse reactions to aspirin is discussed.