NLP drug-medicine extraction

Hi ,

i have been given a sentence where it contains related drug and disease and another non related disease, but i have to extract the correct drug and disease pair .
for example ->

aspirin doses are given to patients having mild headache symptoms and it is not recommended for brain tumor.

from the above sentence ,i have to extract aspirin - headache pair . any idea of how to proceed with this ?
(i have just done stop word removal,pos tagging and word embeddings)

please advice .thanks