Report any rash immediately (Stevens-Johnson syndrome risk).
Before you read
Test yourself first: 5 questions
Question 1 of 5
A client with a head injury and increased ICP is prescribed phenytoin for seizure prophylaxis. Which teaching point and monitoring parameter is most important?
Answer: A. Phenytoin is given to prevent post-traumatic seizures; the nurse monitors the serum phenytoin level (therapeutic range about 10 to 20 mcg/mL) and watches for toxicity such as nystagmus, ataxia, and gingival hyperplasia. Good oral hygiene helps reduce gum overgrowth. Phenytoin is not an analgesic, an osmotic diuretic, or a routine PRN sedative.
Question 2 of 5
A client is taking phenytoin for seizure control. Which finding indicates a common adverse effect the nurse should monitor for?
Answer: A. Gingival hyperplasia (overgrowth of gum tissue) is a well-known adverse effect of phenytoin, and clients are taught meticulous oral hygiene and regular dental care. Other effects include ataxia and nystagmus with toxicity. Phenytoin does not characteristically cause hyperglycemia from dosing as described, bradycardia at therapeutic oral doses, or improved gum health.
Question 3 of 5
The nurse reviews the laboratory report for a client on phenytoin. The therapeutic serum range is 10 to 20 mcg/mL. A level of 28 mcg/mL would MOST likely produce which finding?
Answer: A. A phenytoin level above 20 mcg/mL is toxic. Signs of phenytoin toxicity include nystagmus, ataxia, slurred speech, confusion, and drowsiness. A level of 28 mcg/mL is well above range and would likely cause these neurologic signs. Improved seizure control with no side effects, hypertension with bradycardia, and bright clear vision are not features of toxicity.
Question 4 of 5
A client on long-term phenytoin should be taught to:
Answer: B. Practice good oral hygiene (gingival hyperplasia), maintain a steady dose/level, never stop abruptly (seizures), and report rash. Levels are 10–20 mcg/mL.
Question 5 of 5
A woman taking an oral combined contraceptive is prescribed an antibiotic and an enzyme-inducing antiepileptic. Which teaching is most important regarding the drug interaction?
Answer: B. Certain enzyme-inducing drugs (such as rifampin and several antiepileptics like phenytoin and carbamazepine) can decrease the effectiveness of oral contraceptives. The client should use a backup method of contraception. Doubling the dose is not advised without provider direction.
Keep the streak going with more questions like these, each with a full rationale.
What is phenytoin?
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.
Key points to remember
- 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.
Nursing priorities
- 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.
Labs & values
Patient teaching
- 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.
Red flags: report now
- Report any rash immediately (Stevens-Johnson syndrome risk).
- Report nystagmus, ataxia, or slurred speech (toxicity).
- Never stop abruptly, which can trigger status epilepticus.
References
Clinical references for this topic
