Which drug is commonly used for induction of anesthesia?

Etomidate is widely recognized in clinical practice as a preferred agent for the induction of anesthesia, particularly in emergency and rapid sequence intubation scenarios. This medication is valued for its rapid onset and minimal cardiovascular effects, making it safer for patients who may have compromised hemodynamics.

The pharmacological properties of etomidate allow for a quick transition from consciousness to unconsciousness, which is essential during procedures requiring sedation or anesthesia. It enhances patient safety and comfort by facilitating smooth induction without significant fluctuations in vital signs.

In contrast, other drugs listed do not serve the purpose of anesthesia induction in the same way. Fentanyl citrate is primarily an opioid analgesic, effective for pain relief but not typically utilized for inducing anesthesia on its own. Enalapril maleate is an antihypertensive agent used for managing blood pressure, while diphenhydramine is an antihistamine often used for allergic reactions and not for anesthesia. Etomidate, with its specific applications and benefits, stands out as the correct answer in this context.