INTRODUCTION

The introduction of effective psychotropic medications in the 1950s transformed the lives of many people with mental health problems, including many older people who would otherwise have lived out their lives in asylums. The drugs that are currently available are powerful pharmaceutical agents and all have significant potential adverse effects. This chapter introduces core concepts in clinical psychopharmacology and outlines the major classes of psychotropics used in older people in the community. It is likely to be of most interest to medical and nursing personnel, although all mental health workers do require a working familiarity with the psychotropic medications commonly used in older people.

CORE CONCEPTS IN PSYCHOPHARMACOLOGY

Psychopharmacology involves the use of medication to treat mental health and behavioural problems. The conceptual model behind the use of drugs to alter states of mind is based on the idea that a person’s mental state reflects, at least in part, the state of their brain neurotransmitter systems. Neurotransmitters are chemical messengers that allow brain cells to communicate with one another. Several neurotransmitters have been found to be suitable targets for drug treatment. These include acetylcholine, dopamine, gamma amino butyric acid (GABA), glutamate, noradrenaline and serotonin. It is beyond the scope of this chapter to provide detailed information about each of these neurotransmitter systems, but there are readily accessible sources of this information in specialised texts (e.g. Stahl 2006).

Effective psychotropic medications mostly employ one of three main mechanisms of action:

For example, commonly used antipsychotic medications work via post-synaptic dopamine blockade, whereas commonly used antidepressant medications work via pre-synaptic inhibition of serotonin reuptake from the synapse.

‘Pharmacokinetics’ refers to what the body does to a drug, whereas ‘pharmacodynamics’ refers to what a drug does to the body. Ageing leads to pharmacokinetic and pharmacodynamic changes, and these changes need to be taken into account when prescribing psychotropic drugs to older people.

PHARMACOKINETIC AND PHARMACODYNAMIC CHANGES IN OLDER PEOPLE

There are a number of normal physiological changes with ageing that are relevant to the way the body handles drugs. Hepatic function declines slowly with advancing age so that drugs detoxified in the liver (most psychotropic drugs other than lithium) take longer to be metabolised. If the ingested drug is in its active form and it is inactivated by hepatic metabolism, then reduced hepatic function might lead to increased serum levels of the drug for a certain dose. This might lead to increased efficacy, but it might lead also to increased adverse effects. Renal function also declines slowly with advancing age so that drugs that are primarily excreted by the kidneys (e.g. lithium) will be eliminated more slowly. Thus, for any given dose, the serum level obtained will be higher and might lead to toxic effects. Other relevant pharmacokinetic factors include absorption from the gastrointestinal tract, metabolism in the gut wall, and protein binding in the bloodstream, although these do not change that much with age. With ageing, there is usually reduced total body water and an increased proportion of fat. The latter prolongs the elimination of lipophilic drugs, including most psychotropic agents. However, there are substantial individual differences in the way the body handles psychotropic drugs due mainly to genetic variation. These genetic differences are reflected in the activity of liver enzyme systems, particularly the cytochrome P450 system (CYP450).

In addition to these changes in what an older person’s body does to a drug, there are changes in the ageing brain that make it more vulnerable to the effects of psychotropic medications. Older people with cerebrovascular disease or with dementia are particularly vulnerable to the effects of psychotropic drugs, and the use of much lower initial doses is prudent.

POLYPHARMACY

Polypharmacy refers to the situation in which a person is prescribed multiple potentially interacting medications. This is a common situation in older people with several chronic illnesses. Use of multiple drugs increases the risk of drug–drug interactions and of the additive effects of the adverse effects of these drugs. Sedative and anticholinergic effects due to combinations of drugs with these properties are a common problem, and often lead to confusion and falls.

In the setting of community treatment, the mental health worker should regularly review all the medications that the people under their care are taking. The assistance of a clinical pharmacist with experience in the use of psychotropic drugs in older people can be invaluable.

PRINCIPLES OF DRUG TREATMENT

Before commencing an older person on a psychotropic drug, there are several important steps that should be undertaken. These include combining information from the psychiatric history and mental state examination (MSE) to arrive at a ‘provisional diagnosis’ of the person’s problem. In selected cases, this diagnosis might be further refined through the use of laboratory investigations and neuroimaging studies, as discussed in Chapter 15. Most of the evidence for the efficacy of drug treatment for mental health problems comes from conducting clinical trials in people with a defined mental health problem. Thus, it is important to arrive at a diagnosis before embarking on treatment with psychotropic medication. A physical examination is also important to exclude any contraindications to drug treatment. For instance, certain antipsychotic drugs might be contraindicated in older people with postural hypotension (low blood pressure on standing). It is also important to review with the person their therapeutic responses to previous treatments and any adverse effects that they have experienced in the past. A past history of response to a particular drug often provide a good indication of which drug to choose.

Drug treatment of mental health problems should take place in the context of a biopsychosocial management plan. The medications prescribed should be recorded in the clinical file and progress notes made each visit. Laboratory tests are required when using certain drugs, such as lithium and clozapine. In older people being treated on a voluntary basis, informed consent should be obtained before treatment with psychotropic medication. The person should be provided with detailed information about their diagnosis and the rationale behind drug treatment. They should be told about the common adverse effects of the drug, any uncommon serious adverse effects, and any adverse effects that might have particular significance for them. This can really only be achieved by talking with the person at some length and allowing them time to have their questions answered. It is important also to explain the likely interval to the onset of therapeutic effects and the need for laboratory monitoring, if relevant. The drug dose and dosing interval must be titrated against therapeutic and adverse effects. The drug should be stopped if it doesn’t work.

DRUG ADMINISTRATION ISSUES

In older people, poor eyesight and impaired cognition may increase the potential risk of medication errors. Older people also have a high prevalence of arthritis that affects their ability to open pill bottles. Several techniques have evolved to assist older people living in the community. These include the use of home medication dispensing systems, such as the Webster Pak®, and the use of daily visits from domiciliary nurses to ensure correct administration of medications. In people with less severe difficulties, the use of a ‘pill organiser’, such as a Dosette® box, can help with keeping track of daily medication use. It often helps if the medication regimen has been simplified to once daily. Prescribers should also consider carefully the route of administration. It is often safer to use transdermal delivery systems (skin patches) for potentially toxic medications, such as buprenorphine (a narcotic analgesic) or rivastigmine (a cholinesterase inhibitor medication for Alzheimer’s disease).

There is an important role for case managers in community older persons’ mental health teams in assisting the older preson with adherence to their prescribed medication. Liaison with prescribing doctors and dispensing pharmacists is essential to safe and effective use of psychotropic medication. Case managers are likely also to have an important role in monitoring people for adverse effects from medication. Mental health workers often find it useful to develop working relationships with hospital and community pharmacists. Older people are commonly on complex treatment regimens, and it can be very useful to have a clinical pharmacist review the medication that an older person is taking to look for potential problems.

ANTIDEPRESSANTS

Antidepressant drugs are widely prescribed for depressive and anxiety disorders. The best evidence is for their use in major depression and generalised anxiety disorder, although they are also commonly used in other depressive and anxiety disorders. All antidepressants have similar efficacy in major depression, with approximately 70% of people showing a treatment effect in clinical trials, although 30–40% of this is a placebo effect. The number needed to treat (NNT) (see Ch 3) is between three and four. However, the effectiveness of antidepressants depends critically upon the person’s adherence to the treatment regimen. As a consequence, antidepressant effectiveness is usually considerably less than the level of drug efficacy found in clinical trials.

The main classes of antidepressants are the selective serotonin reuptake inhibitors (SSRIs), the serotonin and noradrenaline reuptake inhibitors (SNRIs), the selective noradrenaline reuptake inhibitors (also abbreviated as SNRIs), the tricyclic antidepressants (TCAs) and the monoamine oxidase inhibitors (MAOIs). There are also several newer antidepressants that are difficult to classify into one of these classes. Contemporary first-line antidepressant treatment often involves the use of an SSRI. Examples of SSRIs include fluoxetine, fluvoxamine, sertraline, paroxetine, citalopram, escitalopram and desvenlafaxine. Although there is little to choose between these drugs in terms of efficacy, they do have different adverse effect profiles and this is their main point of differentiation. Fluoxetine has a long half-life, which can be an advantage in people who adhere poorly to their prescribed medication, but can be a problem due to delayed clearance of the drug following its cessation. Fluvoxamine can cause sedation, which can be a useful property in people with prominent agitation. Paroxetine has significant anticholinergic effects, which can lead to delirium.

Although the SSRI drugs are generally safe, they do have a range of adverse effects, including:

Related posts:

Consumers and carers Clinical cognitive assessment Functional assessment Community management of acutely ill older people Palliative and end-of-life care Management of behaviour in dementia

Stay updated, free articles. Join our Telegram channel

Join