Buclizine dihydrochloride (Buclina) is the hydrochloride salt form of buclizine, a piperazine histamine H1 receptor antagonist with primarily antiemetic and antivertigo activities. Buclizine dihydrochloride binds to and blocks the histamine H1 receptor, thereby preventing the symptoms that are caused by histamine activity. Buclizine dihydrochloride exerts its anti-emetic effect by binding to and blocking the muscarinic and histamine receptors in the vomiting center of the central nervous system (CNS). This may prevent activation of the chemoreceptor trigger zone (CTZ) and may reduce nausea and vomiting.

Topoisomerase I Catalytic Actioity Assay [1]: Topoisomerase I Catalytic Actioity Assay: The enzymatic activity is analyzed by the DNA unwinding assay. DNA topoisomerase I, from TopoGEN (1 unit, which is defined as the amount of enzyme that converts 0.5 μg of superhelical DNA to the relaxed state in 30 minutes at 37 °C), is incubated with 0.5 μg of 6x174 RF DNA, in the presence or absence of Beta-Lapachone, in 20 μL of relaxation buffer (50 mM Tris (pH 7.5). 50 mM KCI, 10 mM MgCl2, 0.5 mM dithiothreitol, 0.5 mM EDTA, 30 μg/mL bovine serum albumin) for 30 minutes at 37 °C. Reactions are stopped by adding 1% SDS and proteinase K (50 μg/mL). After an additional 1-hour incubation at 37 °C, the products are separated by electrophoresis in 1% agarose gel in TAE buffer (0.04 M tris acetate, 0.001 M EDTA). The gel is stained with ethidium bromide after electrophoresis. The photographic negative is scanned with an NIH image analysis system.