A patient is prescribed phenytoin for seizures. What adverse effect must they report immediately to their healthcare provider?

Phenytoin, an anticonvulsant medication, is known to potentially cause serious skin reactions. Among the adverse effects associated with this medication, a skin rash is particularly concerning because it may indicate a serious condition such as Stevens-Johnson syndrome or toxic epidermal necrolysis, both of which can be life-threatening. Immediate reporting of any rash to a healthcare provider is crucial to ensure timely intervention, which may include discontinuing the medication and addressing the reaction.

Other symptoms, while they may warrant discussion with a healthcare provider, do not carry the same level of urgency as a skin rash. Weight gain and headaches are generally less alarming and more common among a variety of medications, whereas muscle weakness could be an indication of other, less immediate concerns or side effects related to dosage or other factors. Nonetheless, the immediate need to address a skin rash emphasizes the importance of vigilance regarding adverse reactions to phenytoin.