Pharmacists, many of whom can speak good English, are an excellent source of information for all things medical. Aside from speaking to a pharmacist, I advise going to the Centro de Salud (Local Health Clinic) or the ER of a hospital in a large town / city to seek assistance. Someone will speak English.
However, it would help if you had your PHP prescription to present. Even in English, an online translator app should be able to use your camera to do a credible translation into Spanish.
Also, absent being able to speak to a pharmacist or doctor in Spanish, or English, the Google and Bing online translators now handle two-way spoken translations fairly well. Practice before you need it.
If it were me, and based on prior experiences, I would use the Translator and Notes apps to prepare a script to hand (show) to a health care professional to read. This should make your circumstances and requests very clear.
The health care system in Spain is excellent! Over the years, I have paid out of pocket for doctor and hospital services. In Spain, a pilgrim will pay dollars for things that would cost hundreds of dollars in the US.
Parenthetically, I actually have private insurance coverage in the US that is usable overseas. But, because paying out-of-pocket was so reasonable, I have never needed to rely on insurance cover - knock wood.
Hope this helps.
Tom