👤 By the CinnaRN Clinical Content Team🕐 Updated 2026-08-23🏷️ Pharmacological Therapies🔖 Free to read, print, and share
Also known as: Dilantin · seizure medicine · anticonvulsant
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Use this quick-reference guide to spot, treat, and prevent Phenytoin on the NCLEX. Keep it handy during review and on exam day!
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📒 The 1-minute cheat sheet
🧪 Labs
Therapeutic: 10–20 mcg/mL
Toxic: nystagmus, ataxia, slurred
🎓 Teach
Gingival hyperplasia → oral care
Never stop abruptly → seizures
Take same time daily
🚩 Report
Rash → stop, SJS risk
IV: only NS, ≤50 mg/min
🩺 Watch
↓effect of OCPs, warfarin
📚 Phenytoin — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what must be reported, and what to teach.
Phenytoin is an anticonvulsant used to prevent and control tonic-clonic and partial seizures and to treat status epilepticus. It has a narrow therapeutic range and many drug interactions. Memory aid: 'Dilantin causes Dental (gingival) overgrowth.' Key principle: monitor levels and never stop abruptly.
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Key points
Understand these first
Therapeutic serum level is 10-20 mcg/mL; toxicity causes nystagmus, ataxia, and slurred speech.
Gingival hyperplasia (overgrown gums) is a classic long-term side effect.
IV phenytoin must be given slowly (no faster than 50 mg/min) and only with normal saline to prevent precipitation and cardiac arrhythmias.
It can cause Stevens-Johnson syndrome and other serious rashes.
It interacts with many drugs and decreases the effectiveness of oral contraceptives.
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Nursing priorities
What to do, in order
Monitor serum drug levels and report values outside 10-20 mcg/mL.
Administer IV doses slowly with a filter, using saline only, with cardiac monitoring.
Assess for early toxicity signs: nystagmus, ataxia, confusion, and slurred speech.
Implement seizure precautions and maintain a patent airway.
Inspect the oral cavity and reinforce dental hygiene.
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Red flags — report now
Escalate immediately
Report any rash immediately (Stevens-Johnson syndrome risk).
Report nystagmus, ataxia, or slurred speech (toxicity).
Never stop abruptly, which can trigger status epilepticus.
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Labs & values
Numbers to know
Phenytoin therapeutic 10-20 mcg/mL
Albumin 3.5-5.0 g/dL (low albumin raises free phenytoin)
CBC to monitor for blood dyscrasias
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Patient teaching
What patients must know
Brush and floss daily and see a dentist regularly to limit gum overgrowth.
Take at the same time each day and do not stop suddenly.
Use a backup birth control method and report rash, fever, or sore throat.
❓ Phenytoin: NCLEX FAQs
What are the priority nursing interventions for Phenytoin?
Monitor serum drug levels and report values outside 10-20 mcg/mL. Administer IV doses slowly with a filter, using saline only, with cardiac monitoring. Assess for early toxicity signs: nystagmus, ataxia, confusion, and slurred speech. Implement seizure precautions and maintain a patent airway.
What are the warning signs of Phenytoin a nurse must report?
Report any rash immediately (Stevens-Johnson syndrome risk). Report nystagmus, ataxia, or slurred speech (toxicity). Never stop abruptly, which can trigger status epilepticus.
What do I need to know about Phenytoin for the NCLEX?
Therapeutic serum level is 10-20 mcg/mL; toxicity causes nystagmus, ataxia, and slurred speech. Gingival hyperplasia (overgrown gums) is a classic long-term side effect. IV phenytoin must be given slowly (no faster than 50 mg/min) and only with normal saline to prevent precipitation and cardiac arrhythmias. It can cause Stevens-Johnson syndrome and other serious rashes.
What patient teaching is important for Phenytoin?
Brush and floss daily and see a dentist regularly to limit gum overgrowth. Take at the same time each day and do not stop suddenly. Use a backup birth control method and report rash, fever, or sore throat.
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Quick Tip
Therapeutic serum level is 10-20 mcg/mL; toxicity causes nystagmus, ataxia, and slurred speech.