I Am 75 Years Old, Female. I Was Recently Dx

I am 75 years old, female. I was recently Dx with Shingles. My doctor gave me a Rx for Acyclovir 800mg. And, Nortriptyline 10 mg capsules.
After reading about Nortriptyline on your website, I understand this to be a medication for depression.
I am not depressed, or have I discussed depression symptoms with my doctor. Why would the doctor prescribe Nortriptyline with a Dx of Shingles?

I did not realize I had to pay for your services. Therefore, please disregard my question.

I am sorry I bothered you.
Thank you.