I often see on TV ads for lawyers who say they represent individuals who have been prescribed specific medications. I have been prescribed this medication, does this mean I have a claim?

You may or may not have a claim.  An analysis of this question will require a focus on the circumstances under which you were prescribed the medication, the dosage you were prescribed, whether or not you have other prescriptions or health factors which would make this prescription ill advised and a host of other considerations.  It is important that you consult a lawyer experienced in such cases so that a proper analysis to present your claim can be made.