Which synthetic opioids are often compared in terms of strength to morphine?

Fentanyl and acetyl fentanyl are synthetic opioids that are significantly stronger than morphine. Fentanyl is estimated to be 50 to 100 times more potent than morphine, making it a critical drug in both medical use and discussions about opioid safety and misuse. Acetyl fentanyl is another synthetic opioid derived from fentanyl that is even stronger than its parent compound. This potency is a major reason why these substances are often the focus when discussing opioids in relation to morphine.

In contrast, while options involving carfentanil and U-47700 also pertain to opioids and can be potent, fentanyl and acetyl fentanyl are more directly compared to morphine within clinical and safety discussions. Heroin and oxycodone are opioids but their strength is often less than fentanyl, and codeine and hydrocodone are typically regarded as weaker in comparison to morphine. Thus, choice A accurately highlights the synthetic opioids that are often discussed in terms of their potency relative to morphine.