A client who is taking dextroamphetamine-amphetamine extended-release tablets for attention deficit hyperactivity disorder (ADHD), reports about having difficulty sleeping at night. Which assessment is most important for the nurse to obtain?

A. Inquire about perceived anxiety: While anxiety can cause insomnia, in this scenario the client is already on a stimulant medication, which is a more likely cause. Asking about anxiety may be useful later, but it is not the first priority for identifying the root of the sleep disturbance. B. Ask about the client's bedtime routine: Bedtime habits do affect sleep quality, but this is a secondary concern when the client’s medication timing could directly cause insomnia. Assessing routines may be more helpful once medication-related causes are ruled out. C. Determine what time the dose is taken: Dextroamphetamine-amphetamine is a stimulant that can cause insomnia if taken too late in the day. Early morning dosing helps minimize interference with nighttime sleep. Identifying dose timing can guide medication scheduling adjustments. D. Determine daily caffeine intake: Caffeine can worsen insomnia, but stimulant medications like dextroamphetamine are generally much stronger contributors. While caffeine intake is relevant, it is less urgent to assess than medication timing in this case.