Price elasticity of demand

Which do you think has a higher price elasticity of demand, Pain-B-Gone, a pain-relieving medication available over the counter in many drugstores, or chemotherapy treatment that uses drugs to destroy cancer cells? Explain your answer. In your explanation, discuss the existence of substitutes, and describe what would happen to equilibrium price and quantities of these two products should supply for either of them shift downward (and to the right). You will of course need to consider the demand curves of each product, and where and how they intersect the supply curves.)