Is any medice applied to someone to make them suffer less when they're about to die?

There are several depending on the persons condition and their need for medication.

Yes, as part of palliative care.

Palliative care provides those with a serious or chronic illness – from the time of diagnosis throughout the course of treatment – care that optimizes quality of life by anticipating, preventing, and managing suffering. It is delivered by an interdisciplinary team of physicians, nurses, social workers, chaplains, and other practitioners to address the physical, intellectual, emotional, social, and spiritual needs of patients and their families.

Yes.