Dexamethasone is almost one of the most commonly used drugs for postoperative nausea and vomiting (PONV) prevention. However, PONV is still a complex problem to be solved; for example, even with preoperative dexamethasone administration, there are still some patients undergoing craniotomy still experience PONV within 24 hours postoperatively. Compared to dexamethasone, dexamethasone palmitate has a long-lasting anti-inflammatory effect, 2-5 times that of traditional water-soluble dexamethasone, with fewer adverse effects. This trial aims to assess the effect and safety of preoperative dexamethasone palmitate on PONV after craniotomy.