Beagle mix medicine question?

Gave my beagle the recommended 2.0 mg of Xanax (Alprazolam) to sedate her enough to clip her and trim her nails (which is becoming increasingly difficult as time goes by.) She STILL panicked......fought like mad, even though she was uncoordinated and sleepy appearing. Let loose with her glands, wailed, cried, fought, snapped....obviously it was NOT enough. She weighs 30 lbs and I am afraid to give her more. CAN I give her more; she is an otherwise very healthy 4 year old. Just terrified of storms and grooming. And vacuum cleaners. ;-)