The duration of drowsiness from oxycodone can vary depending on the dose, formulation, and individual factors. For immediate-release (IR) forms, sleepiness usually starts within 30–60 minutes after taking the medication and may last 4–6 hours. Extended-release (ER) formulations  Factors such as metabolism, age, liver function, and whether other sedating substances are used can also influence how long drowsiness persists. Over time, the body may develop tolerance, and mild fatigue often decreases with continued, properly monitored use.