There is very good advice above about bringing enough medication to last the duration of your Camino, plus travel time on both ends. I do that. But, on occasion have made errors in counting.
In addition to doing that, I use this handy method to bring copies of the prescriptions with me. I take six medications daily for a variety of chronic problems. Hey, if you live long enough, something or another will chase you down and jump on your back...
What follows is actually a LOT easier than it sounds. In my usual manner, I tend to over explain things...
When I exhaust a prescription bottle and obtain a replacement from my local pharmacist, I carefully peel off the label from the empty bottle before I recycle the plastic bottle. I have a piece of clear plastic (a clear sheet protector) that I affix the removed label upon. This makes removing the label later easier. Also, I arrange the labels on the clear plastic sheet in alphabetic order by name of medication.
As I process through successive refills throughout the "off-season," I update the label by removing the previous label and affixing the new label from the most recently empty bottle in it's place.
As I make my final preparations to leave for my annual Camino, or my month-long volunteer stint at the Pilgrim Office in Santiago, or to travel anywhere for a week or more for that matter, I take the plastic sheet protector with prescription labels affixed and make a copy of it on my multi-purpose printer. I also scan the sheet with labels into a .pdf file, stored on my iPhone, using an app called Scan+. Just making a photo of the sheet of labels will also work.
Doing this, I can either view, print or attach the image of the plastic sheet with prescription labels on it, as needed. The hard copy rides with my passport and vaccination records, in a waterproof envelope. A copy of the scanned image file also resides on my iCloud account.
On the few occasions where I needed more of a prescription medication, I went into a farmacia and showed the printed or image copy to the pharmacist. I stated that I needed more of this medication. For items for which I had a prescription label, I have never had a problem.
If you need something NOT on your list, simply ask. Farmacists in Spain have amazing latitude to sell you medications that would be by prescription only at least in the US.
I hope this helps.