Diltiazem Gel was always prepared with hydroxyethyl cellulose. But this raw material is no longer available. What alternative do you recommend?

It is of course unfortunate that hydroxyethylvcellulose (HEC) is no longer available. This polymer preferred for certain applications. This means that the pallet of raw materials, which is available to the pharmacist, has become a little smaller.  

As an alternative is thought primarily to HPMC 4000 but I fear that with this product a sticky gel is sometimes obtained. On the other hand, Carbomer is known for the elegant gels that can be prepared with this polymer. Obviously diltiazemH (+  )   is incompatible with Carbomeer (-). But provided addition of something more trometamol, diltiazemH + can be converted into the   non-ionized diltiazem base; The additional quantity can be calculated on the basis of the molecular masses. If you do not obtain the required viscosity  , add small amounts of trometamol until you reach a pH of 7 to 8.