It's a well known fact in the pharmaceutical industry that different salt forms of a drug have different absorption rates. Some can actually even be more toxic than others. That is why drugs are approved for use by salt form. For example, if a hydrochloride is approved by the FDA, a fumarate would need separate approval requiring new tests or selling it would be illegal even though the hydrochloride was approved by the FDA.

The only form of DMT ever approved for research by the FDA is DMT fumarate. A licensed researcher cannot test any other form of DMT without getting it approved first.