Another modern drug delivery technique is the Osmotic Pump. This is one of the most complex oral sustained-release systems, where the design allows for a controlled release rate of active drug to be released in the gastrointestinal tract of the patient via osmotic pressure. The osmotic pressure in the GI tract is practically the same throughout (~7.5 atm), which allows for this controlled rate to be possible. This type of drug delivery is independent of GI motility, pH, drug loading dose, and other factors that usually limit the bioavailability of the drug.