HESI RN Medical Surgical Practice Exam Related

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A serum phenytoin determination is prescribed for a client with a seizure disorder who is taking phenytoin (Dilantin). Which result indicates that the prescribed dose of phenytoin is therapeutic?

  • A. 3 mcg/mL
  • B. 8 mcg/mL
  • C. 16 mcg/mL
  • D. 28 mcg/mL
Correct Answer: C

Rationale: The correct answer is 16 mcg/mL (Choice C). The therapeutic serum phenytoin range is typically 10 to 20 mcg/mL. A level below this range may lead to continued seizure activity, indicating subtherapeutic levels. Choices A, B, and D are below the therapeutic range and would not be considered therapeutic for a client with a seizure disorder on phenytoin therapy.