A client with a seizure disorder is seen at the clinic for a follow-up visit and a prescription renewal for phenytoin. Which assessment finding warrants immediate intervention by the nurse?

C. Double vision.Double vision, or diplopia, can indicate phenytoin toxicity, which is a serious condition that may lead to impaired vision and increased risk of falls or injuries. This side effect suggests that the patient may be experiencing adverse reactions to the medication, necessitating prompt evaluation and intervention, such as checking serum phenytoin levels and possibly adjusting the medication regimen 2 6 .The other options do not require immediate intervention: A. Chronic insomnia is not a critical side effect of phenytoin and may be managed with lifestyle modifications or further assessment. B. Puffy, bleeding gums are common side effects associated with phenytoin (gingival hyperplasia) but are not immediately life-threatening. D. Blood pressure 100/78 mm Hg is within normal limits and does not indicate a need for urgent action