Adverse effects of anticholinergic activity on cognitive functions in Alzheimer's disease

Cumulative Anticholinergic Burden and its Predictors among Older Adults with Alzheimer's Disease Initiating Cholinesterase Inhibitors

BACKGROUND

Cumulative anticholinergic burden refers to the cumulative effect of multiple medications with anticholinergic properties. However, concomitant use of cholinesterase inhibitors (ChEIs) and anticholinergic burden can nullify the benefit of the treatment and worsen Alzheimer's disease (AD). A literature gap exists regarding the extent of the cumulative anticholinergic burden and associated risk factors in AD. Therefore, this study evaluated the prevalence and predictors of cumulative anticholinergic burden among patients with AD initiating ChEIs.

METHODS

A retrospective longitudinal cohort study was conducted using the Medicare claims data involving parts A, B, and D from 2013 to 2017. The study sample included older adults (65 years and older) diagnosed with AD and initiating ChEIs (donepezil, rivastigmine, or galantamine). The cumulative anticholinergic burden was calculated based on the Anticholinergic Cognitive Burden scale and patient-specific dosing using the defined daily dose over the 1 year follow-up period after ChEI initiation. Incremental anticholinergic burden levels were dichotomized into moderate-high (sum of standardized daily anticholinergic exposure over a year (TSDD) score ≥ 90) versus low-no (score 0-89). The Andersen Behavioral Model was used as the conceptual framework for selecting the predictors under the predisposing, enabling, and need categories. A multivariable logistic regression model was used to evaluate the predictors of high-moderate versus low-no cumulative anticholinergic burden. A multinomial logistic regression model was also used to determine the factors associated with patients having moderate and high burdens compared to low/no burdens.

RESULTS

The study included 222,064 older adults with AD with incident ChEI use (mean age 82.24 ± 7.29, 68.9% females, 83.6% White). Overall, 80.48% had some anticholinergic burden during the follow-up, with 36.26% patients with moderate (TSDD scores 90-499), followed by 24.76% high (TSDD score > 500), and 19.46% with low (TSDD score 1-89) burden categories. Predisposing factors such as age; African American, Asian, or Hispanic race; and need factors included comorbidities such as dyslipidemia, syncope, delirium, fracture, pneumonia, epilepsy, and claims-based frailty index were less likely to be associated with the moderate-high anticholinergic burden. The factors that increased the odds of moderate-high burden were predisposing factors such as female sex; enabling factors such as dual eligibility and diagnosis year; and need factors such as baseline burden, behavioral and psychological symptoms of dementia, depression, insomnia, urinary incontinence, irritable bowel syndrome, anxiety, muscle spasm, gastroesophageal reflux disease, heart failure, and dysrhythmia. Most of these findings remained consistent with multinomial logistic regression.  CONCLUSION: Four out of five older adults with AD had some level of anticholinergic burden, with over 60% having moderate-high anticholinergic burden. Several predisposing, enabling, and need factors were associated with the cumulative anticholinergic burden. The study findings suggest a critical need to minimize the cumulative anticholinergic burden to improve AD care.

Polypharmacy in Multiple Sclerosis: Prevalence, Risks, and Mitigation Strategies

PURPOSE OF REVIEW

Polypharmacy, the use of ≥ 5 medications, is common in people with multiple sclerosis and is associated with negative outcomes. The use of multiple medications is common for symptom management in people with multiple sclerosis, but risks drug-drug interactions and additive side effects. Multiple sclerosis providers should therefore focus on the appropriateness and risks versus benefits of pharmacotherapy in each patient. This review describes the prevalence and risks associated with polypharmacy in people with multiple sclerosis and offers strategies to identify and mitigate inappropriate polypharmacy.

RECENT FINDINGS

Research in people with multiple sclerosis has identified risk factors and negative outcomes associated with polypharmacy. Medication class-specific investigations highlight their contribution to potentially inappropriate polypharmacy in people with multiple sclerosis. People with multiple sclerosis are at risk for inappropriate polypharmacy. Multiple sclerosis providers should review medications and consider their appropriateness and potential for deprescribing within the context of each patient.

Asthma and Chronic Obstructive Pulmonary Disease as a Comorbidity and Association with the Choice of Antidementia Medication Among Persons with Alzheimer's Disease

BACKGROUND

Asthma and chronic obstructive pulmonary disease (COPD) are common comorbidities in persons with Alzheimer's disease (AD). However, pharmacotherapy of these diseases may have opposite mechanisms of action; anticholinergics in asthma/COPD and acetylcholinesterase inhibitors (AChEI) in AD.

OBJECTIVE

To investigate whether existing asthma/COPD affects the choice of AD medication, and the survival of the patients with AD.

METHODS

In this retrospective cohort study, data from the MEDALZ-study, which includes all community-dwelling persons with AD during 2005-2011 in Finland (n = 70718) was utilized. Persons with asthma/COPD (N = 7211) were defined as having a special reimbursement for asthma/COPD, or long-term use (≥250 days) of inhaled anticholinergics, inhaled corticosteroids, or leukotriene antagonists during the year before AD diagnosis. We compared persons with and without asthma/COPD regarding the choice of the initial antidementia medication (AChEI versus memantine) with logistic regression and mortality with Cox regression model during the follow-up (up to end of 2015).

RESULTS

Memantine was favored over AChEIs as first-line treatment to AD in persons with asthma/COPD compared to those without asthma/COPD (odds ratio 1.23, 95% confidence interval (CI) 1.15-1.31). Memantine was also more commonly used among those who used multiple asthma/COPD medications (7.9% of memantine initiators used ≥3 asthma/COPD medications compared with 5.5% of those who initiated with AChEI). Mortality was higher in persons with asthma/COPD compared to those without asthma/COPD (adjusted hazard ratio 1.10, 95% CI 1.07-1.13).

CONCLUSION

More frequent use of memantine instead of AChEI may result from an attempt to prevent possible worsening of asthma/COPD by AChEIs. Vulnerable persons with both AD and asthma/COPD need individually assessed pharmacotherapy for their medical conditions.

The Effect of Cumulative Anticholinergic Use on the Cognitive Function of Older Adults: Results from the Personality and Total Health (PATH) Through Life Study

BACKGROUND

Multiple comorbidities are common in older adults, resulting in polypharmacy that often includes medications with anticholinergic properties. These medications have multiple side effects, which are more pronounced in the older population. This study examined the association between the use of anticholinergics and changes in the cognitive function of older adults.

METHODS

The study population consisted of 2,222 individuals aged 65-69 years at baseline from the Personality and Total Health (PATH) Through Life Study in Australia. Medication data were obtained from the Pharmaceutical Benefits Scheme (PBS). Cognitive measures were obtained from neuropsychological battery assessment. Exposure to cumulative anticholinergic use was quantified to a total standardized daily dose (TSDD). The association between change in cognitive measures between baseline and 4-year follow-up, and cumulative use of anticholinergic was assessed through generalized linear models.

RESULTS

During the study period, 18.6% (n = 413) of participants filled at least one prescription for anticholinergics. Compared to those not on anticholinergics, participants on anticholinergics were more likely to be woman (62.7% compared to 45.1%) and spent lesser time engaging in vigorous physical activity (0.4 h/week compared to 0.9 h/week). Cumulative use of anticholinergic resulting in a TSDD exceeding 1,095 was significantly associated with poorer performance in Trail Making Test Part B (Model 1: β = 5.77, Model 2: β = 5.33, Model 3: β = 8.32, p < .01), indicating impairment in processing speed.

CONCLUSIONS

In our study, except for speed of processing, other cognitive domains measured were not affected by cumulative anticholinergic use over a 4-year period.

Anticholinergic Drugs in Geriatric Psychopharmacology

Drugs with anticholinergic action are widely prescribed in the elderly population due to their potential clinical benefits. However, these benefits are limited by adverse effects which may be serious in particular circumstances. This review presents different aspects of the use of anticholinergics in old age with a focus in psychogeriatric patients. We critically review published data on benefits and disadvantages of anticholinergics, which are often controversial. Prevalence, pathophysiology and measurement methods of the anticholinergic action of drugs are discussed. We also present the most important drawbacks resulting from its use, including effects on cognition in healthy and cognitively impaired people, in aged schizophrenia patients, emergence of delirium and psychiatric symptoms, influence in functionality, hospitalization, institutionalization and mortality, and the potential benefits and limitations of their discontinuation. Finally, we suggest practical recommendations for the safe use of anticholinergics in clinical conditions affecting elderly patients, such as dementia, schizophrenia and acute hallucinatory episodes, depression, anxiety, Parkinson's disease, cardiovascular conditions and urinary incontinence.

Anticholinergic Exposure and Risk of Pneumonia in Persons with Alzheimer's Disease: A Nested Case-Control Study

BACKGROUND

Risk of pneumonia is increased in persons with Alzheimer's disease (AD). In some studies, anticholinergic drugs (AC) have been associated with an increased pneumonia risk.

OBJECTIVE

We analyzed the risk of pneumonia associated with ACs in persons with AD.

METHODS

We performed a nested case-control study using register-based data from a Finnish nationwide MEDALZ cohort including all community-dwelling persons diagnosed with AD during 2005-2011. Cases were identified based on pneumonia diagnoses (n = 12,442) from hospital discharge and causes of death registers. Up to two controls without pneumonia were matched based on time since AD diagnoses, age, and gender for each case; AC use was measured using Anticholinergic Drug Scale.

RESULTS

Use of AC was associated with an increased risk of pneumonia (adjusted odds ratio (OR) 1.36, 95% confidence interval (CI) 1.29-1.43). However, there was no increased pneumonia risk in persons using level 3 ACs. Incident use was associated with higher risk of pneumonia (OR 2.68, 95% CI 2.15-3.34) than prevalent use (OR 1.48, 95% CI 1.40-1.57). Among persons using cholinesterase inhibitors (AChEIs), risk of pneumonia was increased in persons using also ACs (OR 1.53, 95% CI 1.41-1.66).

CONCLUSION

ACs were associated with an increased risk of pneumonia in persons with AD, especially at the time of initiation of these drugs. AC use was associated with increased pneumonia risk also in persons using AChEIs. This risk should be carefully considered when treating AD patients.

Anti-cholinergic medications for bladder dysfunction worsen cognition in persons with multiple sclerosis

Bladder dysfunction is common in persons with MS (PwMS), often due to detrusor muscle overactivity. Anticholinergic medications are considered the first line treatment for bladder dysfunction and are known to worsen cognition in healthy older adults and in persons with dementia. Yet, it is not known if these medications have the same effect on PwMS. Thus, the Objective of this prospective matched-cohort study was to determine if anticholinergic medications affect objective measures of cognition in PwMS. We recruited PwMS starting either oxybutynin or tolterodine (cases). Cases and controls were tested with the Brief International Cognitive Assessment for MS (BiCAMS) battery prior to starting anticholinergic medications and 12weeks later. The primary outcome was change on the Symbol Digit Modalities Test (SDMT) between groups; secondary outcomes were changes on the other BiCAMS measures. Analysis of Covariance with baseline measures as covariates to assess the significance of between group differences was performed at 12weeks. Forty eight PwMS starting anticholinergic medications and 21 matched PwMS controls were recruited. There was a significant difference (p<0.001) in the change on the cognitive measures over 12weeks between groups. The controls demonstrated improvement, consistent with practice effect, while the cases remained unchanged. This study demonstrates that anticholinergic medications may have a negative effect on cognition in PwMS; further confirmatory studies are needed.

Association Between Anticholinergic Medication Use and Cognition, Brain Metabolism, and Brain Atrophy in Cognitively Normal Older Adults

IMPORTANCE

The use of anticholinergic (AC) medication is linked to cognitive impairment and an increased risk of dementia. To our knowledge, this is the first study to investigate the association between AC medication use and neuroimaging biomarkers of brain metabolism and atrophy as a proxy for understanding the underlying biology of the clinical effects of AC medications.

OBJECTIVE

To assess the association between AC medication use and cognition, glucose metabolism, and brain atrophy in cognitively normal older adults from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and the Indiana Memory and Aging Study (IMAS).

DESIGN, SETTING, AND PARTICIPANTS

The ADNI and IMAS are longitudinal studies with cognitive, neuroimaging, and other data collected at regular intervals in clinical and academic research settings. For the participants in the ADNI, visits are repeated 3, 6, and 12 months after the baseline visit and then annually. For the participants in the IMAS, visits are repeated every 18 months after the baseline visit (402 cognitively normal older adults in the ADNI and 49 cognitively normal older adults in the IMAS were included in the present analysis). Participants were either taking (hereafter referred to as the AC+ participants [52 from the ADNI and 8 from the IMAS]) or not taking (hereafter referred to as the AC- participants [350 from the ADNI and 41 from the IMAS]) at least 1 medication with medium or high AC activity. Data analysis for this study was performed in November 2015.

MAIN OUTCOMES AND MEASURES

Cognitive scores, mean fludeoxyglucose F 18 standardized uptake value ratio (participants from the ADNI only), and brain atrophy measures from structural magnetic resonance imaging were compared between AC+ participants and AC- participants after adjusting for potential confounders. The total AC burden score was calculated and was related to target measures. The association of AC use and longitudinal clinical decline (mean [SD] follow-up period, 32.1 [24.7] months [range, 6-108 months]) was examined using Cox regression.

RESULTS

The 52 AC+ participants (mean [SD] age, 73.3 [6.6] years) from the ADNI showed lower mean scores on Weschler Memory Scale-Revised Logical Memory Immediate Recall (raw mean scores: 13.27 for AC+ participants and 14.16 for AC- participants; P = .04) and the Trail Making Test Part B (raw mean scores: 97.85 seconds for AC+ participants and 82.61 seconds for AC- participants; P = .04) and a lower executive function composite score (raw mean scores: 0.58 for AC+ participants and 0.78 for AC- participants; P = .04) than the 350 AC- participants (mean [SD] age, 73.3 [5.8] years) from the ADNI. Reduced total cortical volume and temporal lobe cortical thickness and greater lateral ventricle and inferior lateral ventricle volumes were seen in the AC+ participants relative to the AC- participants.

CONCLUSIONS AND RELEVANCE

The use of AC medication was associated with increased brain atrophy and dysfunction and clinical decline. Thus, use of AC medication among older adults should likely be discouraged if alternative therapies are available.

Serum Anticholinergic Activity and Cognitive and Functional Adverse Outcomes in Older People: A Systematic Review and Meta-Analysis of the Literature

INTRODUCTION

Studies have reported associations between serum anticholinergic activity (SAA) and decline in cognitive performance, delirium, and functional impairment. The aim of this meta-analysis was to explore and quantify associations between SAA and adverse cognitive and functional outcomes in older people.

MATERIALS AND METHODS

A literature search in Ovid MEDLINE, EMBASE, PsycINFO and IPA from 1946-2014 was completed. The primary outcomes of interest were cognitive and functional adverse outcomes associated with SAA in older people aged 55 years and above. The Cochrane Risk-Bias assessment tool was used to assess bias in randomised controlled trials (RCTs). The Newcastle-Ottawa Scale was used to assess the quality of non-RCTs. Meta-analyses were conducted for RCTs and cohort studies separately. Heterogeneity was assessed using I2 tests.

RESULTS

The primary electronic literature search identified a total of 1559 records in the 4 different databases. On the basis of full-text analysis, 33 studies that met the inclusion criteria. The review included 4 RCTs, 5 prospective cohort studies, 3 longitudinal cohort studies, 17 cross-sectional studies, and 4 case-control studies. Twenty-four of the retrieved studies examined an association between SAA and cognitive outcomes, 2 studies examined an association with SAA and functional outcomes and 8 studies examined associations between SAA and both cognitive, and functional outcomes. The meta-analysis on 4 RCTs showed no association with higher SAA and cognitive performance (I2 = 89.38%, H2 = 25.53 and p-value = <0.05) however, the pooled data from 4 observational studies showed elevated SAA was associated with reduced cognitive performance (I2 = 0.00%, H2 = 3.37 and p-value = 0.34).

CONCLUSION

This systematic review summarises the limitations of the SAA on predicting cognitive and functional outcomes in older people. SAA measured by receptor bioassay is flawed and its use in older people with multimorbidity and polypharmacy is questionable.

Anticholinergic Exposure During Rehabilitation: Cognitive and Physical Function Outcomes in Patients with Delirium Superimposed on Dementia

OBJECTIVES

We examined the association between anticholinergic medication exposure and subsequent cognitive and physical function in patients with delirium superimposed on dementia during rehabilitation. We also examined length of stay and discharge disposition by anticholinergic medication exposure.

DESIGN

In this secondary analysis we used control group data from an ongoing randomized clinical trial.

SETTING/PARTICIPANTS

Participants with delirium and dementia were enrolled at admission to post-acute care. These 99 participants had a mean age of 86.11 (±6.83) years; 67.6% were women; 98% were Caucasian; and 33% were positive for at least one APOE e4 allele.

MEASURES

We obtained daily measures of cognitive and physical function using: Digit Span; memory, orientation and attention items from the Montreal Cognitive Assessment; CLOX; the Confusion Assessment Method; and the Barthel Index. Anticholinergic medication exposure was measured weekly using the Anticholinergic Cognitive Burden Scale.

RESULTS

Using multilevel models for time we found that greater use of clinically relevant anticholinergic medications in the previous week reduced cognitive and physical function, as measured by Digit Span Backwards and the Barthel index, in the current week. There was no effect of anticholinergic medication use on delirium severity, and APOE status did not moderate any outcomes. Greater use of clinically relevant anticholinergic medications was related to longer length of stay but not discharge disposition.

CONCLUSIONS

For vulnerable older adults, anticholinergic exposure represents a potentially modifiable risk factor for poor attention, working memory, physical function, and greater length of stay during rehabilitation.

Serum Anticholinergic Activity as an Index of Anticholinergic Activity Load in Alzheimer's Disease

We reported a procedure of serum anticholinergic activity (SAA) measurement and the reliability and reproducibility of the receptor binding assay, and we also described the usefulness of SAA measurement reflecting the anticholinergic activity (AA) in the central nervous system (CNS). According to the results of a 10 times repeated measurement of standard atropine binding, the relative error was between -5.5 and +3.7%, and we considered that measurement of SAA in our studies is accurate and validated. Downregulation of acetylcholine activates inflammation in both CNS and peripheral tissue, which causes AA in both sites. Therefore, changes of AA in the CNS link with SAA in the peripheral system even if a substance having AA does not penetrate through the blood-brain barrier. Then we redescribe issues that require attention in the measurement of SAA. It is generally defined that any SAA greater than the detection limit of a quantitative atropine equivalent level (≥1.95 nM in our study) is positive. According to previous studies, SAA is considered to be positive when its atropine equivalent is ≥1.95 nM and undetectable when this is <1.95 nM. Nevertheless, as a low SAA can act as AA in the CNS, we should assume that SAA might also be positive if its marker concentration is between 0 and 1.95 nM. In addition, SAA should be measured around 11 a.m. or somewhat later because of the diurnal rhythm of cortisol in humans.

Hypothesis of Endogenous Anticholinergic Activity in Alzheimer's Disease

In this article, we review and repropose our hypothesis of the endogenous appearance of anticholinergic activity (AA) in Alzheimer's disease (AD). First, we introduce our previous articles and speculate that, because acetylcholine (ACh) regulates both cognitive function and inflammation, downregulation of this neurotransmitter causes upregulation of the inflammatory system. AA then appears endogenously with the production of cytokines and the downregulation of ACh in AD. To support our hypothesis, we present a female AD patient whose AA was considered to occur endogenously through her AD pathology. Her serum anticholinergic activity (SAA) was positive at her first visit to our memory clinic, was negative at the 1-year and 2-year follow-up visits, and had become positive again by 3 years. We speculate that the initial positive SAA was related to her AD pathology plus mental stress, and that her SAA at 3 years was related to her AD pathology only. Consequently, we believe that 2 patterns of SAA positivity (and therefore AA) exist. One occurs when the downregulation of ACh reaches a critical level, and the other occurs with the addition of some other factor such as medication, induced illness or mental stress that causes AA to affect AD pathology. Finally, we consider the pharmacotherapy of AD based on the proposed hypothesis and conclude that cholinesterase inhibitors can be used to prevent rapid disease progression, whereas N-methyl-D-aspartate receptor antagonists should be reserved for the treatment of AD that is already in a stage of rapid progression. We also propose a staging schema for patients with AD.

Use of Medicines with Anticholinergic and Sedative Effect Before and After Initiation of Anti-Dementia Medications

BACKGROUND

People with dementia may be particularly sensitive to cognitive impairment induced by anticholinergic and sedative medicines.

OBJECTIVE

This study aimed to examine if utilisation of medicines with anticholinergic and sedative effects changed before and after initiation of anti-dementia therapy.

METHODS

A retrospective cohort study was conducted using Australian pharmacy claim data (Pharmaceutical Benefit Scheme). People with first (index) dispensing for a cholinesterase inhibitor or memantine between 1 January 2009 and 31 December 2010 who were aged 65 years or over at the time of initiation were included. The proportion who received sedatives or anticholinergics in the 6 months prior to and post initiation of anti-dementia therapy was determined.

RESULTS

The cohort included 24,110 patients, with over half aged 75-84 years. Overall, 30 % received any class of anticholinergic or sedative medicine for at least 1 month in the 6 months prior to initiation of anti-dementia agents, and 36 % post initiation. Some patients (6 %) ceased anticholinergics or sedatives post initiation even though they had them in the months prior. However, 12 % commenced therapy with anticholinergics or sedatives post anti-dementia therapy initiation even though they were naïve to them in the 6 months prior to therapy.

CONCLUSION

Medicines with anticholinergic or sedative effects were commonly dispensed in one-third of people with dementia. Prescribers need to consider a review of patients on anticholinergic therapy with cholinesterase inhibitors as the effectiveness of the cholinesterase therapy may be compromised.

Serum anticholinergic activity: a possible peripheral marker of the anticholinergic burden in the central nervous system in Alzheimer's disease

We review the utility of serum anticholinergic activity (SAA) as a peripheral marker of anticholinergic activity (AA) in the central nervous system (CAA). We hypothesize that the compensatory mechanisms of the cholinergic system do not contribute to SAA if their system is intact and that if central cholinergic system deteriorates alone in conditions such as Alzheimer's disease or Lewy body dementia, CAA and SAA are caused by way of hyperactivity of inflammatory system and SAA is a marker of the anticholinergic burden in CNS. Taking into account the diurnal variations in the plasma levels of corticosteroids, which are thought to affect SAA, it should be measured at noon or just afterward.

Donepezil abolishes anticholinergic activity in a patient with amnesia

We report the case of a 74-year-old woman who presented with amnesia and positive serum anticholinergic activity (SAA), which disappeared after treatment with the cholinesterase inhibitor donepezil for 1 year. Her only other regular medications were topical glaucoma preparations. We suggest that mental stress, mild cognitive impairment and Alzheimer's disease pathology combined to generate SAA in this patient. We also consider that SAA may have subsequently become negative because of upregulation of acetylcholine production by donepezil, and because the patient's other medications and physical condition (including glaucoma) remained unchanged during the 1-year period.

Co-morbidity and drug treatment in Alzheimer's disease. A cross sectional study of participants in the dementia study in northern Norway

Background

Inappropriate medical treatment of co-morbidities in Alzheimer's disease (AD) is an increasing concern in geriatric medicine. The objective of this study was to compare current drug use related to co-morbidity between individuals with a recent diagnosis of AD and a cognitively healthy control group in a population based clinical trial in Northern Norway.

Methods

Setting: Nine rural municipalities with 70 000 inhabitants in Northern Norway.

Participants: Participants with and without AD recruited in general practice and by population based screening.

187 participants with a recent diagnosis of AD were recruited among community dwellers. Of 791 respondents without cognitive symptoms, 500 were randomly selected and invited to further clinical and cognitive testing. The final control group consisted of 200 cognitively healthy individuals from the same municipalities. Demographic characteristics, data on medical history and current medication were included, and a physical and cognitive examination was performed. The statistical analyses were carried out by independent sample t-test, chi-square, ANCOVA and logistic regression.

Results

A co-morbidity score was significantly higher in AD participants compared to controls. The mean number of drugs was higher for AD participants compared to controls (5.1 ± 3.6 and 2.9 ± 2.4 respectively, p < 0.001 age and gender adjusted), also when adjusted for co-morbidity. AD participants used significantly more anticholinergic, sedative and antidepressant drugs. For nursing home residents with AD the mean number of drugs was significantly higher compared to AD participants living at home (6.9 ± 3.9 and 4.5 ± 3.3, respectively, p < 0.001).

Conclusions

AD participants were treated with a significantly higher number of drugs as compared to cognitively healthy controls, even after adjustment for co-morbidity. An inappropriate use of anticholinergic and sedative drugs was identified, especially among nursing home residents with AD. The drug burden and the increased risk of adverse reactions among individuals suffering from AD need more attention from prescribing doctors.