Scutellaria baicalensis and a constituent flavonoid, baicalein, attenuate ritonavir-induced gastrointestinal side-effects

Ritonavir, a protease inhibitor drug, is commonly used in AIDS therapy. As with other chemotherapeutic drugs that cause gastrointestinal adverse effects, ritonavir treatment is associated with significant nausea and vomiting. This study investigated whether Scutellaria baicalensis, and its active flavonoid constituent, baicalein, attenuate the gastrointestinal effects of ritonavir. The effects of herb administration were evaluated in ritonavir‐treated rats using a rat pica model, which simulates nausea and vomiting in humans. The effects of herb administration on gastric emptying in rats were also measured. Ritonavir treatment resulted in increased kaolin intake or severe pica, the intensity of which was reduced significantly with S. baicalensis administration (1 mg kg−1; P < 0.05). High‐performance liquid chromatography analysis of S. baicalensis showed the presence of an extremely potent flavonoid constituent, baicalein. The study aimed to determine if baicalein contributed to the anti‐pica effect of the extract. It was observed that baicalein dose‐dependently decreased pica in ritonavir‐treated rats (P < 0.001). In addition to inducing pica, ritonavir also significantly delayed gastric emptying, which could contribute to ritonavir‐induced gastrointestinal dysfunction. When S. baicalensis extract was administered to ritonavir‐treated rats the delayed gastric emptying was significantly attenuated (P < 0.05). The results suggest that S. baicalensis and the constituent baicalein reduce the gastrointestinal dysfunction caused by ritonavir. It is concluded that S. baicalensis may potentially have a role to play in reducing drug‐induced adverse effects.