How long do the effects of xanax (alprazolam) last?

Xanax (alprazolam): The drug has a half life of approximately12-24 hours

Depends on product: Xanax (alprazolam) comes in several different forms, regular PO, ER(extended release) PO and SL. It's effect also depends on age and if you have a medical condition. In general regular Xanax (alprazolam) and SL(sublingual) Xanax (alprazolam) are absorbed quickly with some effect by 1 hour. The onset of effect of the ER tablet is around 8 hours. The effect of Xanax (alprazolam) can last between 12 and 40 hours.

Daily dosing: Usually, xanax (alprazolam) has benefits which last for an entire day. The usual dosage of xanax (alprazolam) is once daily, although results are somewhat individually variable. Too often may result in addiction or habituation, and it is not wise to use too much of this drug. It has many helpful effects however, but a large amount is usually not needed.

Xanax (alprazolam) vs Xanax (alprazolam) XR: Xanax (alprazolam) is a short-acting benzodiazepine w/half-life of 11+hrs in most adults, 16+hrs in elderly & ~20hrs in those w/alcoholic liver disease (https://online.epocrates.com/noFrame/showPage?method=drugs&MonographId=1414). The extended release formulation has half-life of 10-16hrs (https://online.epocrates.com/noFrame/showPage?method=drugs&MonographId=3381&ActiveSectionId=7).