Which of the following medications is NOT used to treat opioid overdose?

The medication that is not used to treat opioid overdose is Digoxin. This medication is primarily used to manage certain heart conditions, such as atrial fibrillation and heart failure, by increasing the force of heart contractions and regulating heart rate. Digoxin has no role in reversing the effects of opioids, which are central nervous system depressants.

In contrast, Naloxone (Narcan) is specifically designed to counteract opioid overdoses by binding to the same receptors as opioids, therefore reversing their effects. Fentanyl, despite being an opioid, is mentioned here likely to highlight that additional opioids do not act as antagonists in overdose situations. Buprenorphine is a partial opioid agonist and can help manage withdrawal symptoms but is primarily used in addiction treatment rather than acute overdose scenarios. Thus, Digoxin is the clear choice as a medication unrelated to the management of opioid overdose.