1. Department of Intensive Care Medicine, Nottingham University Hospitals Trust, Queen's Medical Centre Campus, Derby Road, Nottingham NG7 2UH, UK
2. Department of Elderly Medicine Royal Derby Hospital, Derby DE22 3NE, UK
3. Clinical Pharmacology Unit, University of Edinburgh, Edinburgh EH4 2EH, UK
4. National Poisons Information Service-Edinburgh, Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK