Pain management often involves oral pain medications, but this can come with many side effects. The use of topical agents can help avoid systemic side effects while still being successful in managing pain. Cutaneous analgesia after transdermal application of amitriptyline versus lidocaine in rats.
https://www.ncbi.nlm.nih.gov/pubmed?term=12761001
Topical amitriptyline in healthy volunteers.
https://www.ncbi.nlm.nih.gov/pubmed?term=12945021
Topical analgesics.
https://www.ncbi.nlm.nih.gov/pubmed?term=22440379
Local application of strong opioids and wound-related pain.
https://www.ncbi.nlm.nih.gov/pubmed?term=22216634
Characterization of the antihyperalgesic action of a novel peripheral mu-opioid receptor agonist–loperamide.
https://www.ncbi.nlm.nih.gov/pubmed?term=9915332