Is taking zantac (ranitidine) after advil safe?

Yes: Zantac (ranitidine) is actually used to counteract the irritation from taking advil. If you are taking advil on an ongoing basis it will probably not help with tomach pain (counteract the irritation effects). But if you have stopped the advil zantac (ranitidine) will help any irritation causing the discomfort to heal more quickly than it would do without any treatment.