laxative vs purgative

laxative

noun
  • Any substance, such as a food or in the form of a medicine which has a laxative effect. 

adj
  • Having the effect of moving the bowels, or aiding digestion and preventing constipation. 

purgative

noun
  • something, such as a substance or medicine, that purges; laxative 

adj
  • purging 

How often have the words laxative and purgative occurred in a corpus of books? (source: Google Ngram Viewer )