Mohammed T. Abou-Saleh

Principles and Practice of Geriatric Psychiatry.Editors: Professor John R. M. Copeland, Dr Mohammed T. Abou-Saleh and Professor Dan G. BlazerCopyright & 2002 John Wiley & Sons LtdPrint ISBN 0-471-98197-4 Online ISBN 0-470-84641-0111Drug Misuse in the ElderlyPaul Bown, A. H. Ghodse and M. T. Abou-SalehSt George’s Hospital Medical School, London, UKSubstance misuse occurs mainly in young adults, with most ofresearch focusing on this group. However, increasing age bringswith it multiple pathologies and polypharmacy, with the attendantrisks of dependence upon medication. There is evidence tosupport a growing trend to increased alcohol consumption inthe over-65s, especially among women, while a generation oflifetime drug users are now entering old age 1 . The need forawareness of the possibility of the existence of such a hiddendisorder has never been greater in this age group. The Persianphysician Avicenna described four ages of man: an age of growth,an age of prime, an age of decline and an age of decrepit old age 2 .Those aged 65+ will include individuals in any of the latter threeages. Most research in the field has examined substance misuse bythose in the declining stage.USE, ABUSE AND HARMFUL USEWhen considering drug use among the elderly it is helpful toconsider substances of misuse in three broad categories: medications,both prescribed and non-prescribed; socially sanctionedpsychoactive substances; and illicit substances. Religious, culturaland legal differences result in the same substances, e.g. alcohol orcannabis, being differently categorized around the world. Forexample, alcohol may fall within each of the three categories 3 .Some of the consequences of drug misuse are determined by thestatus of the drug rather than the physical effects of the drug.Difficulties in obtaining a drug supply and financing that use mayaccount for as much harm as the physical effects of the drugsthemselves in younger adults. Among the elderly, drugs from themedicines category are over-represented in cases of misuse whencompared to other age groups. This reflects the increased access tomedicines among this group, allied to the physical and socialbarriers that make accessing other drugs harder for this group.At an intuitive level the clinician may balk at categorizingpatients with poor compliance with misusers of non-therapeuticdrugs. The aetiology, social perception and treatment approachesof the two groups differ markedly. This chapter will focus on drugmisusers who display ‘‘harmful use’’. This is defined as:A pattern of psychoactive drug use that causes damage to health,either mental or physical 8 .This definition allows consideration of individuals sufferingdamage as a result of drug use, irrespective of the nature or thesource of the drug of abuse. It excludes cases where omission of apsychoactive medication may be harmful, e.g. in cases of underuseof antidepressants.Harmful use may be related to a single episode of drug misuseresulting in harm, such as a fall while intoxicated. More often it isa chronic condition associated with a dependence syndrome.‘‘Dependence syndrome’’ describes the cluster of cognitive,behavioural and physical phenomena that are observed whenuse of a substance becomes a greater priority for the individualthan other previously more valued activities. It is characterizedby:. A compulsion to take the substance.. Difficulties in controlling the substance use in terms of timingand levels of use.. Withdrawal symptoms on discontinuation of the substance,with relief of these symptoms on reinstatement of use.. Tolerance or neuroadaptation, where increasing amounts ofthe substance are required to achieve effects previouslypossible at lower doses.. Progressive neglect of alternative activities, due to prioritizationof drug-related behaviour.. Persistant use of the substance in spite of evidence of harmfulconsequences.Presence of three or more of the above features simultaneously inthe last year supports a definite diagnosis of dependencesyndrome, using World Health Organization criteria 9 .PHARMACOKINETICSAgeing is associated with a series of physiological changes thatsignificantly alter the fraction of an ingested drug available for apsychoactive effect. Drug absorption shows little variation withage, despite changes in gastrointestinal motility and acidity,reduced absorption surface and slowed gastric emptying. However,once absorbed, the volume of distribution in an elderlysubject is likely to have changed.Ageing results in an increase in percentage body fat and a fall intotal body water. Hydrophilic drugs, such as alcohol, aredistributed in body water, such that with increasing age thevolume of distribution falls and the peak concentration for a givendose may rise by 20% 10 , resulting in lower levels of intake givingthe same intoxicant effect. Conversely, lipophilic drugs, such asbenzodiazepines and other psychotropics, that are stored in fattytissue will remain in the body for longer but at lower peakconcentrations. A fall in plasma albumin in old age results inincreased bioavailability of protein-bound drugs, such as warfarinand diazepam.Drug elimination occurs primarily through direct excretion ormetabolism. Both routes are reduced in the elderly. GlomerularPrinciples and Practice of Geriatric Psychiatry, 2nd edn. Edited by J. R. M. Copeland, M. T. Abou-Saleh and D. G. Blazer&2002 John Wiley & Sons, Ltd