Neostigmine bromide is primarily used in the medical field to treat myasthenia gravis, a condition characterized by muscle weakness. It works by inhibiting the enzyme acetylcholinesterase, which increases the levels of acetylcholine at the neuromuscular junction, thereby improving muscle strength. It is also administered to reverse the effects of non-depolarizing muscle relaxants used during anesthesia. Additionally, it can be employed in the management of urinary retention and postoperative ileus by stimulating smooth muscle contraction in the bladder and gastrointestinal tract. Its ability to enhance cholinergic activity makes it valuable in various therapeutic applications.