Enzymes of drug metabolism during delirium

Background: delirium is common in ill medical patients. Several drugs and polypharmacy are recognised risk factors, yet little is known about drug metabolism in people with delirium. Objective: the aim of this study was to investigate the activities of plasma esterases (drug metabolising enzymes) in delirium. Design: this was a prospective study of delirium present at time of hospital admission (community acquired) or developing later (hospital acquired) in patients admitted as a medical emergency and aged 75 years or over. Methods: following informed consent or assent cognitive screening was completed on all patients on admission and every 48 hours subsequently. Delirium was diagnosed by Confusion Assessment Method and DSM IV criteria. Blood samples were taken on admission and at onset of delirium if this was later. Four plasma esterase assays were performed spectrophotometrically: acetylcholinesterase, aspirin esterase, benzoylcholinesterase, butyrylcholinesterase. Results: 283 patients (71% of eligible) were recruited, with mean age 82.4 years and 59% female. 27% had community acquired delirium, 10% developed hospital acquired delirium, 63% never developed delirium. On admission the mean activities of all four esterase assays were statistically significantly lower in delirious than non delirious patients. There were no significant differences on admission in any plasma esterase activity between patients with hospital and community acquired delirium. In-hospital mortality was associated with low plasma esterase activities on admission. Conclusion: plasma esterase activities are suppressed during delirium. These data reinforce the need for extreme caution with drugs in this vulnerable population