The majority of people watch films for escapism and entertainment...this is perhaps not the film for this purpose and you shouldn't watch it if you find it distressing.
Unfortunately, the scenes portrayed are exactly the reality thousands of people experience daily. It is heartwrenching and extraordinarily unpleasant, but like many have said, necessary for others to learn from if they choose.
One of the most brutal and honest films I ever saw was "Trainspotting", I often think it should be shown (in it's entirety) to high school students (seniors), it certainly takes the excitement and glamour out of the drug scene.