NAPLEX Question of the Week: Role Reversal

This week's questions focuses on an important area of practice that saves lives: Antidotes

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Which of the following correctly matches the drug with its antidote/reversal agent? Select all that apply.

A. Warfarin - phytonadione

B. Dabigatran - andexanet alfa

C. Diazepam - flumazenil

D. Fentanyl - naloxone

E. Organophosphates - physostigmine

 

 

 

 

 

 

 

 

 

 

Answer with rationale:

 The correct answers are A, C, and D.

Because warfarin is a vitamin K antagonist, phytonadione (vitamin K) can be given as an antidote, making answer A correct. Normally, it is given when INR is > 10 and/or significant bleeding is present. When vitamin K is given IV, it should be administered by slow infusion to minimize risk of anaphylaxis.

Answer B is incorrect because the reversal agent for dabigatran is idarucizumab (Praxbind). Idarucizumab is a monoclonal antibody fragment that specifically binds dabigatran and its metabolites. Andexanet alfa is the agent FDA-approved for life-threatening bleeding associated with apixaban (Eliquis) and rivaroxaban (Xarelto), both of which are factor Xa inhibitors. It works by binding the factor Xa inhibitors and also increases tissue factor-initiated thrombin generation. While edoxaban (Savaysa) is also a factor Xa inhibitor, andexanet alfa is not FDA-approved to reverse its activity. 

 Answer C is correct. Flumazenil is the reversal agent for benzodiazepines. It competitively inhibits the activity at the benzodiazepine receptor site on the GABA/benzodiazepine receptor complex. It is important to keep in mind that using flumazenil for benzodiazepine reversal has an increased risk of seizures and therefore should be only given when absolutely necessary.

 Answer D is correct. Naloxone is an opioid antagonist used in overdoses. It is an opioid antagonist that displaces opioids at opioid receptor sites. It has a very short half-life and in some circumstances may be administered in repeat doses or as a continuous intravenous infusion, especially in cases of overdose with either long half-life opiates (methadone) or dosage forms with extended duration of activity such as fentanyl patches or sustained release morphine formulations. Pharmacists should be familiar with various dosage forms of naloxone as in many states in can be given without a prescription. 

 Answer E is incorrect. The antidotes used in organophosphate poisoning include atropine and pralidoxime. Physostigmine is actually used as an antidote in anticholinergic toxicity such as atropine, scopolamine, benztropine, and Atropa belladonna poisoning. 

 See everyone next week as we continue toward the NAPLEX!

Dr. B

Christopher M. Bland

Clinical Associate Professor, University of Georgia College of Pharmacy

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