A nurse is caring for a client who has been taking phenytoin (Dilantin). The nurse understands that which of the following is a long-term adverse effect of this medication?

A. Hair loss is not a recognized long-term side effect of phenytoin. B. Phenytoin is used to prevent seizures, not cause them; a reoccurrence of seizures may indicate ineffective control or medication issues, but it is not a side effect. C. Hypertension is not typically associated with phenytoin use. D. Gingival hyperplasia, or overgrowth of gum tissue, is a common long-term side effect of phenytoin and requires regular dental hygiene and monitoring.