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J O U R N A L O F T H E R O Y A L S O C I E T Y O F M E D I C I N E
Anticholinergic side-effects of drugs in elderly peopleJacobo Mintzer MD
Old age is accompanied by an increased likelihood of illness,
Peters5 identi®ed 22 categories with signi®cant anti-
and old people take a disproportionate amount of self-
cholinergic activity, including those with an anticholinergic
administered and prescribed medications. In the USA,
Box 1 Drugs with anticholinergic adverse effects used in the elderly
people over 65 consume 30% of prescriptions and 40% of
over-the-counter remedies, despite making up only 13% of
the population1. In the UK, elderly people comprise only
18% of the population but use 45% of all prescription
drugs, some of which are prescribed inappropriately and
without proper attention to side-effects2. Elderly people
living in nursing homes are even more likely to receive
medications and to experience side-effects3. Thus, in one
year, 97% of elderly nursing home residents received a
prescription drug, compared with 71% of patients living in
procyclidine, trihexyphenidyl,ethopropazine
the community4. Failure to identify side-effects can lead to
use of other drugs to treat the symptoms, rather than
adjustment of the dose of the drug responsible.
Why do side-effects go unnoticed in elderly people?
Older people often have low health expectations and are
less likely to complain. Patients with cognitive impairment
have dif®culties in communicating their discomfort; those
living in nursing homes may rely on care staff to alert the
physician to possible side-effects. Some side-effects can be
mistaken for the effects of old age and age-related illness.
This is particularly the case for anticholinergic side-effects,
which are among the most common drug-related effects
experienced by elderly people living in nursing and
residential homes5,6. This review highlights the need for
better understanding, assessment and management of
anticholinergic side-effects in elderly people.
Blazer et al.4 reported that, during one year, nearly 60% of
dexchlorpheniramine,hydroxine, mepyramine
nursing home residents had received drugs with anti-
cholinergic (antimuscarinic) activity, compared with 23% of
elderly people living in the community. The most
frequently prescribed of these drugs were thioridazine,
chlorpromazine and diphenoxylate/atropine. Several types
of drug can cause anticholinergic side-effects (Box 1).
nortriptyline, protriptyline,amoxapine, maprotiline,clomipramine
Medical University of South Carolina, Department of Psychiatry (PH-141), 67
President Street, PO Box 250861, Charleston, South Carolina, 29425, USA;
1School of Psychiatry and Behavioural Sciences, University Hospital of South
Correspondence to: Professor Jacobo Mintzer
J O U R N A L O F T H E R O Y A L S O C I E T Y O F M E D I C I N E
Table 1 In-vitro anticholinergic activity (at 10 nmol/L) of the
does not always predict clinical effects; alternatively, the
25medications most commonly prescribed to elderly people
activity reported by Tune et al., though insuf®cient to cause
obvious side-effects with cimetidine monotherapy in young
adults, might be troublesome in those already receiving
anticholinergic medications or otherwise vulnerable. High
doses of cimetidine in elderly patients have occasionally
been associated with reversible confusional states (confu-
sion, delirium, slurred speech, hallucinations, coma8).
Symptoms which may be caused by drugs with anti-
. Dry or sticky lips; dif®culty beginning to speak (need to
. Urinary disorders, necessitating use of catheter
. Insecure movement; falls without obvious reason,
. Increased anxiety, with rapid, shallow breathing,
mode of action (e.g. drugs for parkinsonism, irritable bowel
syndrome, urinary incontinence) and others with unwanted
Anticholinergic actions affect multiple systems, causing a
anticholinergic effects. Tune et al.7 looked for in-vitro
range of peripheral and central side-effects and symptoms
anticholinergic activity in the 25 drugs most commonly
(Table 2). Central anticholinergic effects include memory
prescribed for elderly people and found such activity in 14
de®cits, confusion and disorientation, agitation, hallucina-
(Table 1). Often, elderly patients receive several such drugs
tions and delirium4,6. In the extreme, anticholinergic
toxicity depresses brain function, with coma and circulatory
Many non-prescription drugs have anticholinergic
potential; this is true of the antihistamines in cold/¯u and
hayfever treatmentsÐe.g. diphenhydramine (Benylin Four
Flu); triprolidine (Actifed); chlorpheniramine (Piriton/
Why should old people be at increased risk of anti-
Contact 400); and promethazine (Night Nurse/Phenergan).
cholinergic side-effects4,9? Part of the reason may lie in
Skin creams and lotions also contain antihistaminesÐe.g.
de®cient drug metabolism and elimination, as well as age-
diphenhydramine (Allereze cream) or mepyramine (Anthi-
related de®cits in cholinergic neurotransmission6. For
san)Ðand treatments for sleep disturbance include
people living in nursing homes, with little to distract them,
diphenhydramine (Nightcalm/Nytol) and promethazine
side-effects can be particularly distressing and dif®cult to
(Sominex/Phenergan). Some hayfever medications contain
cope with. For example, dry mouth, while apparently
theophylline (e.g. Chest-Eze), antidiarrhoeals include
trivial, can cause speech dif®culties, dental decay or trouble
extract of belladonna (Enterosan, Opazimes) and some
with dentures. Chewing and swallowing may become
treatments for irritable bowel syndrome contain hyoscine
painful, and the patient may refuse solid food. The pain of
dry mouth can be extremely distressing for older patients,
The number of drugs with anticholinergic potential
who may become frustrated and agitated by an inability to
available without prescription is increasing6, so that the use
of such medications is becoming more dif®cult to monitor.
Older people often have multiple illnesses. In the USA
For example, histamine H2 antagonists can be had over the
as many as ®ve chronic conditions in one person is not
counter for indigestionÐcimetidine (Tagamet/Acid-eze);
unusual10, and conditions such as angina, congestive heart
ranitidine (Zantac); famotidine (Pepcid AC). Of those drugs
failure, constipation, diabetes mellitus, glaucoma, urinary
examined by Tune et al.7, cimetidine had the highest anti-
dysfunction, sleep disturbance and dementia are all
cholinergic activity in vitro, although side-effects attributed
worsened by drugs with anticholinergic activity6. Pupillary
to this activity do not feature in the labelling of cimetidine.
dilatation and the inability to accommodate will impair near
458 One interpretation is that in-vitro pharmacological activity vision, thus increasing the risk of accidents, including falls,
J O U R N A L O F T H E R O Y A L S O C I E T Y O F M E D I C I N E
Table 2 Spectrum of anticholinergic side-effects (Adapted from Ref. 6)
Impaired perception of taste and texture of food
Mucosal damageDental decay, periodontal disease, denture mis®tMalnutritionRespiratory infection
Increased risk of accidents and falls, leading to
Exacerbation/precipitation of acute angle closure
Faecal impaction (in patients with constipation)
Reduced gastric secretions, gastric emptying
Altered absorption of concomitant medications
Urinary retention, urinary tract infection
Conduction disturbances, supraventricular
Exacerbation of anginaCongestive heart failure
Profound restlessness and disorientation,
Ataxia, muscle twitching, hyperre¯exia, seizuresExacerbation of cognitive impairment (in patients
and may precipitate narrow-angle glaucoma in predisposed
events6. Nevertheless, physicians often attribute anti-
patients. In patients with constipation, anticholinergic
cholinergic symptoms in elderly people to ageing or age-
effects may lead to stomatitis, paralytic ileus or faecal
related illness rather than the effects of drugs6. Even
impaction. Drug-induced increases in heart rate may
physicians and carers who appreciate that such symptoms
worsen symptoms of angina, and inhibition of sweating
can be drug-induced may regard them as inevitable, simply
may cause life-threatening hyperthermia. Patients with
urinary hesitancy may experience urinary retention and
urinary tract infection, a common cause of delirium. Men
with prostatism are at high risk of acute urinary retention as
In their nursing home study, Blazer et al.4 calculated that
Delirium can be caused by blockade of brain muscarinic
between 21% and 32% of residents could have been taking
receptors; drugs with anticholinergic activity are the most
two or more drugs with anticholinergic activity (three or
common cause of drug-induced delirium7,11. More than
more drugs 10±17% of patients; ®ve or more drugs, up to
one-®fth of elderly patients admitted to hospital develop
5%). The most common combinations were thioridazine/
delirium, particularly those with dementia and multiple
benzhexol and thioridazine/chlorpromazine (benzhexol is
illnesses. In patients with dementia, anticholinergic drugs
now seldom used). However, combined use of thioridazine
further inhibit cognitive performance and counteract the
and amitriptyline (each with marked anticholinergic
bene®cial effects of cholinergic enhancers used to treat
activity) was also very common, demonstrating a lack of
concern about combined anticholinergic effects.
Williamson et al.9 examined the use of psychotropics
Partly through legislation, there have been reductions in
and antiparkinsonian drugs (both have marked anti-
the use in US nursing homes of psychotropic drugs, many of
cholinergic effects) in nearly 2000 patients admitted to
which have marked anticholinergic activity12. The avail-
geriatric units. More than a quarter were receiving one such
ability of newer psychotropic drugs has also had an
drug, and 13% of those patients had signi®cant adverse
impact on prescribing by primary care physicians
J O U R N A L O F T H E R O Y A L S O C I E T Y O F M E D I C I N E
treating patients in nursing homes13. With increasing use of
dementia23±25, despite a lack of prospective placebo-
newer psychotropics anticholinergic side-effects in elderly
controlled studies on their use in these circumstances26.
people may be declining, but many different drugs have
Substantial differences exist between conventional neuro-
some anticholinergic activity and elderly patients receiving
leptic drugs with respect to anticholinergic activity;
multiple drugs are still at risk of `anticholinergic load'14. In
chlorpromazine and thioridazine have the highest
theory the physician can predict the anticholinergic load and
activity27,28 with considerable side-effects29 (see Box 1).
the risk of side-effects associated with any combination of
Haloperidol has lower muscarinic af®nity and the risk of
drugs. In practice, the information available from the
anticholinergic side-effects is lower, but extrapyramidal
product label and from the published work focuses on side-
symptoms are more troublesome29. Conventional neuro-
effects of drugs used as monotherapy. The concept of
leptic drugs can also cause other side-effects. Low doses
anticholinergic load illustrates that side-effects can be
have been recommended for elderly patients, although this
caused by combinations of drugs, even if the individual
may limit the ef®cacy of these agents26.
drugs do not cause obvious side-effects.
Novel antipsychotic drugs have been widely studied in
younger patients (particularly those with schizophrenia),
but for most drugs no controlled trials have been reported
in elderly patients26. An exception is risperidone, which has
These are among the most common medications taken by
been compared with placebo in two trials in elderly nursing
elderly people living in nursing homes (mainly anti-
home patients with dementia30,31. Risperidone is the only
psychotics, antidepressants and anxiolytics/sedatives).
novel antipsychotic so far registered for this indication in
Spore et al.15 found that 43% of elderly patients in
certain countries (though not in the UK). It has no
residential care were receiving psychotropic drugs.
measurable anticholinergic activity28 and has not been
Antidepressants and antipsychotics have been linked most
reported to cause anticholinergic side-effects in elderly
often with disorders due to anticholinergic activity.
patients30,31. By contrast, clozapine has marked anti-
cholinergic activity and is associated with profound
anticholinergic side-effects32±34. When clozapine (and other
The use of antidepressants in elderly people requires
antipsychotics with high anticholinergic activity) are with-
particular care16,17. Tricyclic antidepressants (TCAs) have
drawn, two types of withdrawal reaction are seenÐ
been in use for over 30 years, and imipramine and
`cholinergic rebound', with nausea, vomiting, loss of
amitriptyline are the standard against which new drugs are
appetite, malaise, diarrhoea, rhinorrhoea, sweating,
evaluated. Old patients are more likely than young adults
anxiety, agitation and insomnia35,36; and movement
to experience side-effects with TCAs (see Box 1 for
disorders such as dyskinesia, akathisia and parkinsonism37.
examples). Apart from the postural hypotension and
When switching patients to a drug with low anticholinergic
sedation associated with the TCAs, anticholinergic side-
potential, physicians sometimes mistake withdrawal symp-
effects such as constipation, urinary retention and
toms for the side-effects of the new drug.
confusion are particular causes for concern. Some
authorities have advised against the use of TCAs such as
imipramine, amitriptyline and doxepin in the elderly
because of their side-effects, not least their anticholinergic
Physicians should be alert to the possibility that dry mouth,
effects18±20. Nortriptyline, lofepramine and desipramine
constipation and blurred vision may be caused by
(the least anticholinergic of the TCAs) tend to be better
medication. Changes in intellectual function should also
be investigated, especially in patients who already have
Some newer antidepressants may be useful alternatives
cognitive impairment. For patients in whom side-effects can
to TCAs in elderly people21. The selective serotonin
have particularly unpleasant consequences (e.g. those with
reuptake inhibitors such as ¯uoxetine and sertraline have
gastrointestinal disease, bladder neck obstruction, glau-
been recommended, partly because of their relative
coma, cardiac disease or cognitive impairment), serious
freedom from anticholinergic side-effects19,20. Nefazodone,
consideration should be given to switching to a drug that
bupropion, venlafaxine and mirtazapine also have less
anticholinergic potential than the older drugs22.
For most drugs with anticholinergic potential an
alternative is available. Combinations of drugs with strong
anticholinergic activity, such as thioridazine and amitripty-
line, should obviously be avoided. The use of drugs with
Conventional neuroleptic drugs are widely used in the
minimal anticholinergic activity from the outset should
460 treatment of behavioural and psychological symptoms of avoid the need to switch medication (and the risk of
J O U R N A L O F T H E R O Y A L S O C I E T Y O F M E D I C I N E
cholinergic rebound). If switching is necessary, the hazard
3 Furniss L, Burns A, Craig S, Cooke J, Scobie S. The effect of a
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For patients already receiving treatment, the current
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5 Peters NL. Snipping the thread of life. Antimuscarinic side effects of
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8 Martindale the Extra Pharmacopeia. London: Pharmaceutical Press, 1989
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8272 Moss Landing Road Moss Landing, CA 95039 EDUCATION BA Biology Truman State University, Kirksville, MO Moss Landing Marine Laboratories, Moss Landing, CA Research in phycology and community ecology OTHER RELEVANT COURSEWORK 2001 Oregon Institute of Marine Biology, Charleston, OR Graduate coursework in Marine Ecology and Animal Behavior RESEARCH EXPERIENCE 2002 - present MS