the increase in energy likely comes from the ATP effect. Ribose can be very good, but as I said, it has to be used in a proper setting for maximum benefit and not as a sugar replacement.
Talk to the doctor who put you on it and try to understand the rational behind is best for you. Adrenal fatigue is not only about energy loss. Its really a mind-body condition where the internal control is lost. Pouring more gasoline in to car that is out of gas is good provided that the steering wheel and system is in place. Otherwise, the gasoline cannot get you where you want to go properly. Make sure you are taking care of the rest and have a comprehensive recovery program in place that is well rounded and not single focused on energy alone, as that will usually fail and a crash may be triggered over time after the maximum stimulatory level is reached.