Laudanum was routinely administered to Poe on his death bed. Unfortunately, unlike alcoholism, the habitual usage of such substances was almost unavoidable, making addiction inevitable. Ironically the drugs that eased Poe's pain mainly caused by erratic heartbeat and brain fevers also aided in his early death. Unfortunately, his addiction to these drugs contributed to depression as well. After 1846, most of Poe's accounts are filled with references to a general decline in health.
Calomel is a purgative.
At this point, to drink would have been Poe's death, but his pain was too great for him to overcome his addiction. His heartbeat was erratic, and he complained to Annie of a headache that lasted for months. Whether the brain lesion was independent of Poe's other problems or whether an escape through drugs and alcohol caused the brain lesion will never be known. His lifetime definitely showed instances where a brain tumor was the best explanation for Poe's peculiar behavior. As to what actually happened in the last few days of Poe's life, no one really knows.