castor oil experiences?!

So
Today I am 40 weeks exactly, my baby is weighting 4,2kg already (estimated) and I have no signs of contractions. At the appointment today the midwife and doctor gave me a recipe for a "cocktail" I should drink with castor oil and even alcohol... I am so scared of taking caster oil, if they think that baby should come now, why don't they induce me? 
What are your experiences with castor oil?
Thanks a lot!