Physostigmine is a medication used primarily to treat glaucoma and to reverse the effects of certain types of anesthesia. It works by inhibiting the enzyme acetylcholinesterase, which breaks down the neurotransmitter acetylcholine. This leads to increased levels of acetylcholine in the body, enhancing nerve signal transmission. Additionally, physostigmine can be used in cases of anticholinergic toxicity, where it helps counteract the effects of drugs that block acetylcholine receptors. It is administered through injection and requires careful monitoring due to potential side effects, including muscle twitching and increased salivation.