A 64-year-old man with type 2 diabetes presents to the clinic with the complaint of “my feet feel like they are on fire.” He has a loss of vibratory sense, +1 Achilles reflex, and a tack embedded in his left heel. Which of the following would be an appropriate treatment?

a. Tricyclic antidepressants
b. Capsacin cream
c. Vitamin B12 injections
d. Insulin