Which article (por/para) should I use to express that I go to the drugstore for medicine？

Question

1. Voy a la farmacia por medicina.
2. Voy a la farmacia para medicina.

Which is correct?

Answer 1

Wimi's answer is indeed correct. Perhaps there is some confusion on the part of OP around the use of "para". The preposition "para" could be used with an infinitive:

• Voy a la farmacia para comprar medicina.

The preposition "para" can be followed by nouns but not in the case at issue, for example:

• Este dinero es para medicina. (This money is for medicine, i.e. to be spent on medicine.)

With "ir", meaning "go and get", the preposition "por" is required.

Answer 2

As explained by RAE, "going to fetch something" is usually translated as "ir a por algo" in Spain and as "ir por algo" in Latin America. So

Voy a la farmacia a por medicina

and

Voy a la farmacia por medicina

are both correct.

Answer 3

From "Complete Spanish Grammar, 3rd Edition" by McGraw Hill Education:

Para indicates:

• purpose of an action, goal, event or object, equivalent to "in order to"
• comparison contrasting one idea, person, object or situation to others in the same group or category
• deadlines equivalent to "for", "by", or "on" with a time indicator.
• destination being a place or a person
• note that some expressions ending with para cannot be followed by a noun.

Por indicates:

• exchange as "in exchange for" in bartering, commerce, etc
• movement either through a space or area or as "by means of"
• duration with an indication of how long in time
• expressions of time, related to morning, night, etc
• causality as "because of"
• equivalent to per
• some more idiomatic expressions

To answer your question:

por is correct, it can be interpreted that you are going to the pharmacy because of the need for medicine.

To use para, You would rephrase to indicate the pharmacy as your destination (Estoy saliendo para la farmacia) or the purpose of going there (Voy a la farmacia para comprar medicamentos).