Equally illicit fentanyl and carfentanil are extremely unsafe opioids which will produce a quick overdose and Dying when abused, but carfentanil is more strong than fentanyl. Various doses in the anti-overdose drug naloxone (Narcan) might not be effective to reverse an overdose. Keep on readingRe: Really Freaked Out!! Fentanyl OD or W/D, Not sure!