ristocetin

Ristocetin is a glycopeptide antibiotic historically isolated from actinomycetes. It belongs to the same broad class of antibiotics as vancomycin, and, like other glycopeptides, it inhibits bacterial cell wall synthesis by binding to the D-alanyl-D-alanine termini of cell wall precursors. In clinical use, ristocetin was employed to treat certain bacterial infections, but its use declined due to significant toxicity and availability of safer alternatives such as vancomycin. Today, ristocetin is largely obsolete as a therapeutic agent.

Beyond its antimicrobial history, ristocetin remains important in hematology as a diagnostic reagent. It can induce platelet agglutination in the presence of functional von Willebrand factor (vWF), enabling laboratory assessment of vWF activity and platelet receptor function. The test, known as ristocetin-induced platelet aggregation (RIPA) or ristocetin cofactor activity (vWF:RCo) assay, helps diagnose von Willebrand disease and related platelet function disorders. In these assays, patient plasma is mixed with normal platelets and ristocetin; the degree of agglutination reflects the functional interaction between vWF and the platelet GPIb-IX-V receptor complex.

Safety and regulatory status reflect its historical twin roles. While it is no longer used clinically as an antibiotic due to toxicity concerns and the availability of better drugs, ristocetin endures in clinical laboratories for diagnostic purposes related to von Willebrand disease and platelet function testing. Its dual legacy—an antimicrobial history and a pivotal diagnostic reagent in hemostasis—remains a defining feature.