Donepezil, a cholinesterase inhibitor that increases synaptic availability of acetylcholine, improves cognitive function in Alzheimer's disease. Sampson and colleagues [94] randomly assigned 33 elderly patients undergoing elective total hip replacement to donepezil 5 mg or placebo immediately following surgery and every 24 hours for 3 days. Donepezil was well tolerated with no serious adverse events. Although the drug did not significantly reduce the incidence of delirium (9.5% versus 35.7%; P = 0.08) or length of hospital stay (mean ± standard error: 9.9 ± 0.73 days versus 12.1 ± 1.09 days; P = 0.09), both outcomes showed a consistent trend suggesting possible benefit. The authors project that a sample size of 95 patients would be required for a definitive trial.