R/Gel with Tetracaine 3.5%, lidocaine 2.3% in Gel?

There where lidocaine base (we prefer becoming the base) is very well soluble in alcohol this is not the case for tetracaïneHCl.   We therefore need to convert tetracaïneHCl to the base and can do this with trometamol or triethanolamine. For 3.5 G tetracaïneHCl We need 1.4 G trometamol for the conversion to the base.    

We can therefore prepare a hydroxypropylcellulose alcoholic gel consisting of: Hydroxypropylcellulose (HPC)   5.0   G, ethanol 80 g and water 20 g.  

To the ethanol we add HPC,   let that   dissolve and swell; then we add lidocaine base. This should solve it. Once dissolved, mix the tetracaine HCl with the gel  

In The water we dissolve 1.4 G   Trometamol and add it to the gel. TetracaïneHCl should convert to Tetracaine base   and dissolve (solubility in ethanol 1 to 5)