Acetylcholinesterase inhibitors are a class of medications that block the action of the enzyme acetylcholinesterase. This enzyme is responsible for breaking down the neurotransmitter acetylcholine in the body. By inhibiting this enzyme, these drugs increase the levels of acetylcholine, which can enhance communication between nerve cells. These inhibitors are commonly used to treat conditions like Alzheimer's disease and myasthenia gravis. By improving acetylcholine signaling, they can help alleviate symptoms related to memory loss and muscle weakness. However, they may also cause side effects, including nausea and diarrhea, due to increased acetylcholine activity in other areas of the body.