Is sibutramina the same thing as adipex?

No. Adipex is a brand name for phentermine, an amphetamine that is commonly prescribed and fairly well tolerated. Sibutramina is not an amphetamine, but rather has it's appetite suppressing effects through its effects on norepinephrine, serotonin and dopamine. It was sold in the U.S. Under the brand name Meridia but has been taken off the market due to increased risk of cardiovascular complications.
No. Adipex is Phentermine and sibutramine is meridia. They are both classified as appetite suppressants. They function by a different mechanism, however.