It is all very well to say a drug works topically. However it is easy to assume they work on similar mechanisms so one does not add to the other. Phenytoin (Dilantin) augmented both ketamine or Baclofen so might be good in any mix.
J Clin Anesth. 2017 May;38:154-155. doi: 10.1016/j.jclinane.2017.01.040.
Phenytoin in topical formulations augments pain reduction of other topically applied analgesics in the treatment of trigeminal neuralgia.
Kopsky DJ et al.
https://www.ncbi.nlm.nih.gov/pubmed/28372657
- case of ablation trigeminal branch left with dysesthesias; 10% ketamine topically helped initially but needed 10 % phenytoin added to maintain benefit
- another case of post-ablation dysthesias helped initially with baclofen 5% but needed 10% phenytoin to continue benefits.
Comment – given that tolerance to an agent can occur, adding phenytoin makes sense.