I'm looking for an excipient for a 5% Baclofen dermaticum.

The case is not that simple. After all, as the formula shows, this product contains both a basic and an acidic function:  

This product therefore has an isoelectric point, the value of which is = 7.

The gel, which you use for the preparation of Diclofenacgel contains very much triethanolamine and is for that reason unusable.

So it gets a bit of searching. You can leave a regular Carbopol gel to which you add the amount of liquid paraffin and cetomacrogol as in the Diclofenacgel. The Diclofenacgel protocol can be followed for this component.   to the finished gel you add   baclofen. I suppose the Baclofen solves (??)  .   Check the pH, which must have a value = 7   = I.E.P.  

If necessary, one adjusts with triethanolamine, if too low, or with 1% acetic acid, if too high;