Some additions to my first post....
A little background and off topic sorry. Pharmacies are big busniess here. It has been my experience that they are just as much peperos or peperas - slang for pill poppers - but sometimes also pepas are slang for strong benzos such as xanax and 10 mg diazepam, so whatever. I have heard it used in a general sense and also specifically, like the town pepero, who consumes 10 10mg diazepams a day then gets drunk and stumbles incoherently....sidetrack on slang.....as fpr pharmacies, open one up in anew urbanization, maybe if you ar lucky co-locate it with a clinic. Good biz, next thing you have two or three...yeah, it just gets better from there. I was doing some serious due dilligence in this market as well as domestic (peruvian and south american) made pharmaceuticals, careful not to say drugs, connotating something else
Anyway I came across a huge list of all the drugs available in Peru according to their national formulary on the minesterio de salud website. It may be worthwhile to poke around there for an updated list. In the US they all have their trade names and there is the name of the actual drug, so you should be familiar with that.
Next about your specific issue, when you are seen by the dr it will be thier call. If it is a psych drug, go to a psycologist. May be best to do this in Lima as all the drug come from there anyway, and also for the benefit of the possibilty of finding a good clinic with an english speaking dr, if you go to cusco you may either have to order it, or just may not be able to get it. I would suggest a few more things, bring a pill bottle with you, so you can show the dr, and even have your medical records from the us, although you may need them translated.
Lastly you can import drugs to peru, but it is a last step as it is a total pain in the rear, but discuss this possibility with your current perscribing dr, also ask them what they think. I find drs are so ignorant of other countries, even in the age of the internet...social media all that jazz.
I know your drug is available but not under that name, but I do not know the perscribing protocols and they may just not give it to you. Not sure what the laws are on bringing perscription drugs into the country on the plane, but if it is that important of a drug to you, maybe best to try and stockpile a bit and just bring enoungh for your time here.
The one time i decided to import an important perscription drug i couldnt be without, here to peru it was a nightmare. I had to get a corroborating perscription from a peruvian doc, wasted almost 100 bucks there, plus the day running arpund lima, going from customs to some other building where i had to fill out forms, register with some sanitation dept etc. It was so much work, I decided never again. Since then I have found alternative therapies here in peru that, well arenot as effective as the drug, but maybe im saving my liver, who knows. Best of luck and be sure to enjoy cusco. Go to pisac and eat empenadas
Im not a southern peru guy, despite the majority of tourism exists there. Take care.