I've been on venlafaxine for depression for many months, and now my new doctor wants me to take nortriptyline for painful cramps. Are these drugs alr?

Same class. Both drugs are in the same class, Venlaflaxine has more serotonin effect and nortriptyline has more nor epinephrine effect. There is a small risk of possible serotonin syndrome, also side effects may be more pronounced as both are in the same class. PLease discuss this with your doctor.