I believe it is. The only problem though is if the person that is being interrogated will be able to give accurate information due to the lack of sleep. If I do not get a lot of sleep then I am not able to think straight at all and that is with out other interrogation techniques going on.
The purpose of an interrogation is to gather facts. Sleep deprivation over a long period of time causes unhealthy side effects such as hallucinations and even death. Information derived from someone who may be suffering from hallucinations cannot be trusted and, therefore, defeats the purpose of using sleep deprivation to garner it. It is also not okay to put someone's life at risk in the process of an interrogation.