34 Psychopharmacology in women with learning disabilities

This chapter outlines some of the main issues concerning psychopharmacology in women with learning disabilities. Review of recent literature shows that women’s mental health has been explored increasingly closely over the last 30 years but for the most part women with learning disabilities unfortunately have been excluded from these studies. This is despite women with learning disabilities having different needs and challenges, due to their particular situation and unique mental health needs (Romans 1998). The following chapter briefly reviews these matters, and gives practical guidance to a pragmatic approach to psychiatric drug prescribing for this high profile patient group.

The chapter opens with an overview of general issues concerning gender, health, and psychotropic prescribing for women with learning disability. A brief summary of general guidelines to be followed in prescribing psychotropics for this population closes the chapter. Throughout the chapter, advice on common clinical scenarios is presented in the form of ‘practice points’.

Historically, clinical practice in the psychiatry of learning disability has been largely centred on the male population (Aman 1983). Meeting the health needs of women with learning disabilities requires consideration of the interactions between their experiences and needs at each stage of the life span and the interface with social, economic, and cultural environments, including gender-specific issues, in addition to those which are common across both genders. Meeting the health needs of women with learning disabilities, including a rational approach to their psychopharmacology entails consideration of their sexual development, sexuality, the menstrual cycle, aspects of contraception, fertility, reproduction, puerperium, and menopause: all of which are unique to women, or are at least gender-specific.

To date, however, little attention has been paid to addressing gender-specific issues relating to the health needs of women with learning disabilities (Ayd 1991). The reasons for this are numerous, including a long tradition of a lack of attention being paid to the needs of women in learning disability services, a lack of appreciation of the reproductive healthcare needs of women with learning disability, and a general lack of interest in gender-specific issues with respect to pharmacological interventions.

On the positive side, there is evidence of some shift in contemporary approaches to the predicament of women with learning disabilities, which signify that there are initiatives in progress to redress these inequalities. For example, the general shift towards a health service which aims to reduce all health inequalities has direct relevance to the situation of women with learning disabilities, and consequentially to prescribing of psychotropic medication for them. In face of this, it is now incumbent upon us to consider whether there are any such inequalities which are gender-specific, to address these, and to ensure that women’s needs in this respect are met. One of the issues highlighted by the recent report by Mansell (Department of Health 2007) concerns drug prescribing for behaviour disorder. In common with a number of previous documents, it is highlighted here that many people with severe learning disabilities—and especially women—are likely to receive drug treatment for behaviour disorders and self-injurious behaviour. This is therefore one of a set of contemporary documents which emphasizes the need to consider other strategies, and where possible, avoid getting into a trap of inappropriate psychotropic prescribing in women with learning disabilities who have challenging needs.

At present the literature is sparse on topics related to psychopharmacology for women with learning disabilities. Research on the prevalence of mental health problems in individuals with learning disabilities has largely overlooked the issue of gender, and there is a tendency for women’s physical health problems to go unrecognized and untreated, due to diagnostic overshadowing—even more than among men with learning disabilities (Kohen 2001). Some of the confounding factors include biological predisposition to certain illnesses, and the social circumstances of this extremely vulnerable group of people.

Reproductive and physical health has direct relevance to the prescribing of psychotropic medication. Standard guidelines and formularies for drug prescribing are substantially geared towards otherwise healthy individuals, while also taking account of health conditions and intercurrent prescribing thereof. Compared with women in the general population, women with learning disabilities have several characteristics that increase their risk for reproductive and physical health conditions. These include higher rates of hypogonadism and failure to menstruate, early menopause, and high levels of comorbid conditions such as epilepsy, hypothyroidism, and obesity (Carr and Hollins 1995). In addition to this set of factors, there are the general observations that there is a high frequency of psychotropic medication in this population, and that these women tend to have a relatively sedentary lifestyle. Also, among women with learning disabilities, the average age at onset of menarche is similar to that of women in the general population. Taken together, these interplaying factors highlight the need for a careful, cautious approach to initiating and psychotropic prescribing in women with learning disabilities, where there is such a high rate of comorbidity, and need to be aware of any intercurrent prescribing.

When the physician embarks on psychotropic drug prescribing in women with learning disabilities, care is required in selection, introduction, and manipulation of dose and other aspects of drug treatment, in order to maximize efficacy and minimize side effects and toxicity, which can readily occur in this population (Arnold 1993). This entails consideration of pharmacokinetics, drug interactions, and treatment/compliance monitoring—and how these relate to the special needs of women with learning disabilities (O’Brien 2002).

Pharmacokinetics refers to the process of distributions of drugs within the body and their concentration within various body tissues. It encompasses drug absorption, excretion, and metabolism. Appropriate dosage regimens for starting medication in women with learning disabilities often vary from the general population—the cautious approach to be taken in clinical practice is to start at lower dosage, and to increase dose slowly. Other considerations can then be made, depending on the characteristics of the individual patient, and the specific drug.

Gender differences in body composition, weight, and physiology affect drug absorption, distribution, biotransformation, and excretion. Crucially, women have 11% more body fat than men and this results in initially lowered serum levels of most psychopharmacological agents. Certain other key differences between the physiology of women and men are also of direct relevance to psychotropic prescribing. In comparison with men, women have lower bone mass and lower muscle mass. Males and females also have structural differences in various organs including heart, brain, and gastrointestinal system, in addition to the different sexual organs and respective sexual hormonal systems. The sex hormones (oestrogens and androgens) are physically important in both males and females, and play an important role at various stages in a person’s development. They are vital in the sexual differentiation prenatally, during the maturation phase in adolescence, in menstruation and pregnancy. Oestrogen and progesterone significantly drop at menopause in women and there is a gradual decline in testosterone with ageing in both men and women.

For the most part, starting doses of psychopharmacological agents do not vary between the sexes. However, women whose body mass vary substantially from the norm, can show significant changes in pharmacokinetics. In those psychopharmacological agents in which serum level of drug is crucial, special caution must be initiated in monitoring dose levels, and in manipulating these over the course of therapy – especially in lithium, carbamazepine, and other agents where serum level of active ingredient is crucial for effective psychopharmacological intervention.

The blood pressure is 5–10 mmHg lower in women than men. This difference disappears after menopause. The average heart rate is higher in women than age-matched men. Furthermore, the QT interval is found to be longer in women than among men—these factors need to be taken into account when initiating treatment with any medication which can alter QT interval, especially antipsychotic medication, and also some antidepressant drugs.

Certain antipsychotics and antidepressants have a significant impact on Q–T interval. It is crucial, in preparing to prescribe these agents for women with learning disabilities, that the full pretreatment investigation protocol should be carried out, including electrocardiogram investigation.

The glomerular filtration rate is slightly lower in young women than age-matched men. It may decline more rapidly with aging in men than women. This clearly has implications on the blood levels of various psychopharmacological agents. For the body concentration of many agents—notably antipsychotic and sedatives—may all too quickly become toxic, with disastrous consequences for the general health and well-being of women with learning disabilities. It is therefore important that, particularly among older subjects, such women be monitored by specialist physicians who are familiar with the change in renal function of older people, and understand the needs for careful manipulation of drug dosage. This needs to be routinely accompanied by monitoring of kidney function, in addition to monitoring of serum levels of those psychopharmacological agents where this is appropriate and available.

In prescribing psychopharmacological agents in women with learning disabilities, it is important to bear in mind the reduced glomerular filtration rate and renal function in the elderly, to monitor for any signs of toxicity, utilizing serum level of drug where available.

Gender differences have been noted in rates of hepatic metabolism, possibly due to the inhibitory effect of oestrogen on some hepatic microsomal enzymes. By delaying gastric emptying time, progesterone may influence drug absorption. Oestrogen and progesterone, both highly protein-bound, may compete with psychotropic medications for protein binding sites. Free, unbound levels of medications may vary with reproductive hormone levels. Competitive binding and microsomal enzyme induction are therefore routine matters to be addressed in all psychopharmacological prescribing, in balancing maximal efficacy with minimal side effects and toxicity. In practice among women with learning disabilities, the physician must give careful attention to the measurable health and body function indices, through routine investigations, in order to clarify the precise internal biochemical milieu of the patient.

The prescribing physician must take account of the effects of hepatic metabolism on bioavailability of psychopharmacological agents, especially in the presence of other drugs, notably those affecting sex hormone functioning.

Women with learning disabilities are likely to experience the same spectrum of adverse effects from psychotropic drugs as does the general population. In addition, these women may be at increased risk of experiencing side effects which may be unrecognized or ignored, for various reasons. For example, in a person with moderate learning disabilities with communication difficulties, the sedating signs resulting from toxicity of many psychotropic agents may be difficult to distinguish from pre-existing functional disability. Women with learning disabilities in the mild to moderate range potentially may be able to describe some problems which are drug side effects, but they may not be able to attribute these adverse effects as being drug-induced. People with severe to profound learning disability may be unable to recognize or report side effects because of impairments or deficits in speech.

Individual variation in medication response is greater in people with learning disabilities, due to the impact of brain development on the pharmacodynamics of a given medication. Also, such is the tolerability of antipsychotic drugs among women, that extrapyramidal and anticholinergic reactions are more often experienced by them. Furthermore, psychotropic drugs are among the most common groups of drugs to adversely affect sexual and reproductive function. However, sexual side effects caused by psychotropic drugs tend to be underestimated, because some patients are reluctant to report such intimate issues and indeed other have such major communication difficulties. Moreover, vulnerability to sexual dysfunction caused by psychotropic medication generally increases with age. These effects need to be borne in mind by the prescribing physician, who needs to routinely monitor the effects of medication on sexual functioning.

In prescribing psychopharmacological agents, the physician should be aware of the higher incidence of the common extrapyramidal and anticholinergic side effects among women, of the impact of medication on sexual functioning, and that the patient will frequently not identify these health problems as drug side effects.

With improved longevity in the learning disabled population, we need to consider the impact of ageing on psychopharmacological prescribing in women with learning disability. Despite it being a common experience, very little attention has been paid to the menopause among women with learning disabilities. Also in this population, the drug treatment of dementia and mental health problems poses special challenges. Great care is required in selection, introduction, and manipulation of dose and other aspects of drug treatment of these patients, in whom side effects and toxicity frequently occur. Staff caring for people in this spectrum require training and awareness of the additional problems faced with advancing age. Again the increasing rates of physical morbidity in older women with learning disabilities need to be addressed accordingly.

Gender is a critical determinant of mental health and mental illness. Gender determines the differential power and control men and women have over the socioeconomic determinants of their mental health and lives, their social position, status and treatment in society, and their susceptibility and exposure to specific mental health risks.

Gender differences occur particularly in the rates of common mental disorders—depression, anxiety, and somatic complaints. These disorders, in which women predominate, affect approximately one in three people in the community and constitute a serious public health problem. Depression is not only the most common women’s mental health problem but may be more persistent in women than men. Depression is found to be twice as common in women than men in the general population (McGrath et al. 1990). A study by Hastings et al. (2004) of a population based sample of over 1000 adults with learning disabilities showed a significantly increased rate of affective and neurotic symptoms in women than men. Apart from the well-recognized risk factors like stress, life events, female gender, low socioeconomic status, lack of social support, and old age, people with learning disabilities are further disadvantaged by their limited coping skills, experiences of discrimination, stigma, and abuse.

There are no marked gender differences in the rates of severe mental disorders such as schizophrenia. From time to time, minor gender differences have been reported in age of onset of symptoms, frequency of psychotic symptoms, course of disorder, subsequent social adjustment, and long-term outcome of disease, but despite these debates, there remain no significant gender differences here. In the general population, the course of schizophrenia is more favourable in women, who tend to have a later onset of the illness, fewer negative symptoms, more prominent mood symptoms, and a better treatment response to the illness than men (Seeman and Fitzgerald 2000). For these reasons, women tend to be diagnosed with schizophrenia at a later stage as they are often misdiagnosed as having a mood disorder (Castle 2000). There is very little research in this area on women with learning disabilities in particular.

Eating disorders are more common in women than men. Anorexia nervosa and Bulimia nervosa occur much more frequently in women than men (10:1) (Romans 1998). The extent to which this is common in people with learning disabilities is yet to be fully ascertained. More often, in this population, it is postulated that weight loss is likely to be secondary to other problems such as depression or adverse life events, rather than a wish to become thin.

Additional research is needed in this area to understand more about these issues and the role of increased awareness of such issues as well-being and body image among women with learning disability.

Women with learning disabilities have the right to be given information about what is happening to their bodies, and to learn about the experiences of other women. There is a need to support them in a proactive manner. The use of accessible audio-visual aids can facilitate their understanding of these matters, as can targeted staff training and support. Working in partnership with families and professional carers can be pivotal in improving compliance with medication. Encouraging women to live a healthy lifestyle and ensuring access to primary healthcare is the bedrock of a holistic approach to the management of the mental health of women with learning disabilities.

When possible, prescribing of drugs should be based on clinical diagnosis. Psychiatric disorders are relatively common in this population and there is a wide scope for pharmacological interventions; however, many of the behavioural constellations do not constitute diagnosable psychiatric disorders (Eaton and Menolascino 1982). In this situation, prescribing may be informed by the responsiveness of individual behaviour types to certain drugs.

The evidence base for psychopharmacological agents in the mental health and behaviour problems of women with learning disabilities is sparse. Current prescribing practice in learning disabilities largely draws on evidence from the general population and adjustments are to be made on an individual basis.

A conservative approach to the use of medication is required. Most behavioural problems in this clientele do not merit drug treatment, particularly those that are brief, self-limiting, caused by intercurrent physical health problems, or caused by environmental stressors. However, certain diagnosable disorders such as depression merit prompt rather than last-resort drug therapy.

This should be guided by a simple rule—‘start low, go slow’. An initial dose of one-half of the adult dose is usually recommended to minimize side effects. Increases to the full dose should be undertaken over twice the period of time used in mainstream practice.

It is very important to avoid polypharmacy due to the potential adverse interactions between various agents. However, if the individual patient needs a mixture of medication, it is good practice to document the need and to monitor side effects accordingly and to work closely with the pharmacists.

Under the Capacity Legislation, it is recognized that each individual should be free to make personal choices for themselves, according to their capacity to understand the choice made and the implications of that choice. This is a crucial matter for those with learning disability—especially where choices concerning medication have to be made. When a person is assessed to be unable to make such an informed choice, then all relevant professionals concerned in their care must act in their ‘best interests’, while making every effort to ascertain their wishes (Mental Capacity Act 2007). The UN Convention on the Rights of Persons with Disabilities (December 2006) highlights the following as some of the salient recommendations to be addressed: equality between men and women, equality of opportunity, respect for individual autonomy and dignity and inclusion in society.

Psychotropic prescribing in the care of women with learning disabilities needs to be planned and implemented as part of a holistic care plan. In general, a conservative approach towards psychotropic drug prescribing is advisable, in which other non-drug interventions are explored before any inception of psychopharmacological agent. More research is needed to explore possible gender differences in the manifestation of mental illness among people with learning disability, and the implications of this on pharmacological management. The development of person-centred planning, partnerships between various agencies, and evidence-based practice provide a strong foundation for further positive changes in the provision of care for women with learning disabilities, particularly where any gender specific interventions might be planned accordingly.