Antidotes Cheat Sheet for the NCLEX
Every drug-antidote pairing the NCLEX tests: NAC, naloxone, flumazenil, vitamin K, protamine, DigiFab, deferoxamine, calcium gluconate, glucose, oxygen.
Memorize the pairings cold. The NCLEX gives you the overdose; you supply the antidote and the monitoring that goes with it.
Acetaminophen → N-acetylcysteine (NAC)
Hepatotoxicity is the danger and it is delayed. Patients look fine for the first day while the liver fails. Draw a level at 4 hours post-ingestion and plot it on the Rumack-Matthew nomogram. NAC works best within 8-10 hours but is still given late. Oral NAC smells like rotten eggs; mix with juice. IV NAC can cause an anaphylactoid reaction (slow the rate, don't panic).
Opioids → naloxone
The trigger is respiratory rate, not sedation level. RR under 12 with pinpoint pupils after opioids = give naloxone. Naloxone wears off before most opioids do. Watch for re-sedation and be ready to redose. In dependent patients it precipitates acute withdrawal, so titrate to adequate breathing, not full alertness.
Benzodiazepines → flumazenil (with caution)
Flumazenil reverses benzos but is rarely used in practice. In chronic benzo users or mixed overdoses with TCAs it can precipitate seizures, and the only drug that would treat those seizures is now blocked. On the exam: know the pairing, and know why supportive care usually wins.
Warfarin → vitamin K
Vitamin K (phytonadione) rebuilds clotting factors over hours to a day. Actively bleeding patients cannot wait that long: they get FFP or prothrombin complex concentrate for immediate factors, plus vitamin K for the durable fix. High INR without bleeding: hold warfarin, consider oral vitamin K.
Heparin → protamine sulfate
Protamine binds heparin directly and works fast. Give slowly IV; rapid administration drops blood pressure. It partially reverses enoxaparin, fully reverses unfractionated heparin. aPTT confirms the reversal.
Digoxin → digoxin immune Fab (DigiFab)
Reserved for serious toxicity: unstable arrhythmias, K+ above 5 in acute overdose, hemodynamic compromise. Not for a mildly elevated level in a stable patient. Remember the setup question: hypokalemia makes digoxin more toxic at the same level.
Iron → deferoxamine
Iron overdose is a classic pediatric poisoning (prenatal vitamins look like candy). GI symptoms come first, then a deceptive quiet phase, then shock and liver failure. Deferoxamine chelates iron and turns the urine a red-orange color. That color change means it is working, not that something is wrong.
Magnesium sulfate → calcium gluconate
Mag toxicity progresses in order: lost deep tendon reflexes first, then respiratory depression, then cardiac arrest. Check reflexes before anything else. Keep calcium gluconate at the bedside of every patient on a mag drip, especially OB patients on seizure prophylaxis.
Insulin excess → glucose
Conscious and able to swallow: 15 g fast-acting carbohydrate, recheck in 15 minutes, repeat if still low. Unconscious: IV dextrose (D50), or IM glucagon if there is no IV access. Never put juice in an unresponsive patient's mouth.
Carbon monoxide → oxygen
CO binds hemoglobin about 200 times more tightly than oxygen. Pulse oximetry reads falsely normal because it cannot tell carboxyhemoglobin from oxyhemoglobin. Treatment: 100% oxygen by non-rebreather, hyperbaric oxygen for severe cases and pregnant patients. Diagnose with a carboxyhemoglobin level, not SpO2.
Frequently asked
Fastest way to memorize these?
Pair them as flashcards and drill both directions. The NCLEX asks 'which antidote' and 'this antidote treats what' about equally.
Why is flumazenil risky when naloxone isn't?
Blocking benzos in a dependent or mixed-overdose patient can trigger seizures with no benzo available to stop them. Naloxone withdrawal is miserable but not lethal.
Is atropine an antidote too?
Yes, for organophosphate (insecticide) poisoning and cholinergic crisis. It also treats symptomatic bradycardia.
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