Back pain and paracetamol, blood thinning drugs, drug driving, kidney stones

Mark Porter investigates a new research trial which shows that paracetamol doesn't help back pain. And why are blood thinning drugs being overused in NHS hospitals? New laws on limits for driving on prescribed drugs come into force in March 2015. Which prescription drugs are included and what does it mean for people taking them? Also in the programme, can any medications help get rid of kidney stones?