Prescribing for the older patient

Introduction¹

Older adults require special care and consideration when prescribing medications. Older adults often receive multiple drugs for multiple diseases. This greatly increases the risk of drug interactions as well as adverse reactions, and may affect compliance. The balance of benefit and harm of some medicines may be altered in older adults. Therefore, medicines should be reviewed regularly and medicines stopped when not clearly beneficial. Always balance the potential harm and benefits of any medicine. Also, non-pharmacological measures may be more appropriate in many situations.

In much older adults, manifestations of normal ageing may be mistaken for disease and lead to inappropriate prescribing. In addition, age-related muscle weakness and difficulty in maintaining balance should not be confused with neurological disease. Disorders such as light-headedness not associated with postural or postprandial hypotension are unlikely to be helped by drugs.

Prophylactic drugs may be inappropriate if they are likely to complicate existing treatment or introduce unnecessary side-effects, especially in older adults with poor prognosis or with poor overall health. However, older adults should not be denied medicines which may help them, such as anticoagulants or antiplatelet drugs for atrial fibrillation, antihypertensives, statins, and drugs for osteoporosis.

When prescribing, each older adult must be considered individually apart from just their age. Other considerations must include comorbidities and frailty, as well as their own preferences.

STOPP/START criteria

Various strategies have been developed to identify older patients at risk from adverse effects and to reduce the risk of initiating drugs likely to cause adverse events - eg Screening Tool of Older Person's Prescriptions (STOPP) and Screening Tool to Alert doctors to Right Treatment (START).^{2 3}

The STOPP/START criteria are evidence-based criteria used to review medication regimens in older adults. STOPP (Screening Tool of Older Persons' potentially inappropriate Prescriptions) aims to reduce the incidence of medicines-related adverse events from potentially inappropriate prescribing and polypharmacy. START (Screening Tool to Alert to Right Treatment) can be used to prevent omissions of indicated, appropriate medicines in older patients with specific conditions.

Form of medicine

Frail older adults may have difficulty swallowing tablets. Ulceration may develop if left in the mouth. Their tablets or capsules should always be taken with enough fluid, and whilst in an upright position to avoid the possibility of oesophageal ulceration. It can be helpful to discuss with the patient the possibility of taking the drug as a liquid if available.

General issues¹

The nervous system of older adults is more sensitive to many commonly used drugs, such as opioid analgesics, benzodiazepines, antipsychotics, and antiparkinsonian drugs, all of which must be used with caution. Similarly, other organs may also be more susceptible to the effects of drugs such as anti-hypertensives and NSAIDs.

Pharmacokinetic changes can markedly increase the tissue concentration of a drug in older adults, especially in debilitated patients:

• The most important effect of age is reduced renal clearance. Many aged patients thus excrete drugs slowly, and are highly susceptible to nephrotoxic drugs. Acute illness can lead to rapid reduction in renal clearance, especially if accompanied by dehydration. A patient stabilised on a drug with a narrow margin between the therapeutic and toxic dose (eg, digoxin) can rapidly develop adverse effects in the aftermath of a myocardial infarction or a respiratory-tract infection.

• The hepatic metabolism of lipid soluble drugs is reduced in older adults because there is a reduction in liver volume. This is important for drugs with a narrow therapeutic window.

Adverse reactions often present in older adults in a vague and non-specific fashion. Confusion is often the presenting symptom (caused by almost any of the commonly used drugs). Other common manifestations are constipation (with antimuscarinics and many tranquillisers) and postural hypotension and falls (with diuretics and many psychotropics).

Avoid symptomatic prescribing

Take care that you are not prescribing an agent to 'treat' a normal aspect of ageing - for example, alteration in the sleep/waking cycle. Where an older patient presents with new symptoms it is wiser to conduct a thorough assessment and attempt to reach a diagnosis before prescribing. The masking of symptoms may undermine your ability to detect an evolving illness. Symptomatic prescribing in the older patient tends to lead to a vicious cycle of polypharmacy, adverse effects and further prescribing to treat these new 'symptoms'.

Consider the effect of non-prescribed medication

As with younger patients, it is important to recognise that patients may be taking OTC or complementary preparations which could interact with prescribed agents. Another factor to take into account is the use of previously prescribed agents, or even drugs prescribed for someone else. Try to take a full drug history and involve members of the older patient's family if necessary, in order to obtain a true picture of what is actually being taken. Find out what your patient understands about the various medications that they are taking, how they should be taken and how they affect them, before adding in another agent.

Adverse drug reactions in older patients

ADRs may present in nebulous and nonspecific ways in older patients.

• Confusion can be caused by virtually any drug.

• Constipation, dizziness, dry mouth, and blurred vision are other common side-effects in older patients.

• Falls are associated with a poor prognosis in older patients and are often associated with medication. A systematic review found an increased incidence of falls in older patients taking benzodiazepines, antidepressants and antipsychotics. A weaker link was identified with antiepileptics and drugs that lowered blood pressure.⁴

• When assessing symptoms in an older patient, take their medication into account and question whether or not this might be iatrogenic disease.

Side-effects of specific drug classes¹

NSAIDs

• Gastrointestinal bleeding is more common and has more serious consequences in older patients.

• NSAIDs can worsen heart failure or aggravate impaired renal function. These effects can be worse in older adults.

• They are best avoided, if possible, for simple pain relief in osteoarthritis (OA), etc; paracetamol should be tried instead and, if this is insufficient, try a low-dose NSAID in addition, with proton-pump inhibitor (PPI) or misoprostol cover, or substitute a low-dose opioid.

• For soft-tissue lesions, and back pain, first try measures such as weight reduction (if obese), warmth, exercise, and use of a walking stick.

• Consider complementary therapies such as acupuncture to help with pain management.

• The co-prescription of NSAIDs and ACE inhibitors in older patients can be a recipe for disaster; their combined deleterious effect on renal cortical perfusion and function can lead to significant renal impairment in the older patient.

Diuretics

• This class of drugs is often overprescribed in older adults and should not be used for chronic treatment of gravitational oedema where measures such as leg-raising, increased walking/leg exercises and graduated compression stockings are often sufficient.

• A few days of diuretic treatment may speed the clearing of the oedema but it should rarely need continued drug therapy.

• Where diuretics are used to treat hypertension or cardiac failure, they should be reviewed regularly, along with an assessment of the patient's state of hydration and U&Es if necessary.

• Withdrawal of diuretics requires careful monitoring and consideration of potential contra-indications to withdrawal and can be difficult to achieve. For example, patients with well-controlled heart failure can develop troublesome symptoms and blood pressure can rise significantly in hypertensive patients.

Hypnotics

It is much better to take a good history of an older patient's sleep habits and suggest sleep hygiene and non-pharmaceutical measures to overcome insomnia, than to prescribe drugs, which at best will be a temporary solution.

Many hypnotics with long half-lives have serious hangover effects, including drowsiness, unsteady gait, slurred speech, and confusion. Hypnotics with short half-lives may also be a problem and should only be used for short periods if essential.

Short courses of hypnotics are occasionally useful for helping through an acute crisis but every effort must be made to avoid dependence. Benzodiazepines impair balance, which can result in falls. In patients prone to falls or dizziness avoid using these agents unless absolutely necessary.

Digoxin

In the older adults, the daily maintenance dose should be 125 micrograms. In the renally impaired, the dose should be 62.5 micrograms. 250 micrograms/day is likely to cause toxicity.

Drugs that cause bone marrow suppression

Drugs such as co-trimoxazole and chloramphenicol should only be used if there is no suitable alternative.

Anticoagulants and antiplatelet drugs

• Beware of gastrointestinal bleeding and contra-indications such as peptic ulceration which may have occurred a long time ago and been forgotten about.

• Oral anticoagulants:

  • Direct-acting oral anticoagulants (DOACs) may need dose-reduction in older adults and more frequent monitoring to ensure the dose remains appropriate.

  • For warfarin, prescribe only when patients have a full understanding of why the drug is being taken, its dangers, correct daily dosing/timing and the importance of regular INR monitoring.

Antidepressants

• Tricyclic antidepressants commonly cause postural hypotension and confusion in the older patient; they should be used carefully.

• Serotonergic medications used for depression may cause serotonin syndrome and agitation in the older patient; this can be difficult to distinguish from some of the symptoms of depression.

Diabetic medication

• Long-acting oral hypoglycaemics such as chlorpropamide and glibenclamide should be avoided as there is a significant risk of hypoglycaemia when these agents are used in the older patient.

• Consider relaxing the target HbA1c level on an individual basis and in discussion with older adults with type 2 diabetes, with particular consideration:⁵

  • For people who are frailer.

  • If they are unlikely to achieve longer-term risk-reduction benefits, eg reduced life expectancy.

  • Tight blood glucose control would put them at high risk if they developed hypoglycaemia, eg risk of falling or if they drive.

  • If they have impaired awareness of hypoglycaemia.

  • If intensive management would not be appropriate, eg if they have significant comorbidities.

Guidance¹

• Always consider whether a drug is indicated at all.

• It is a sensible policy to prescribe from a limited range of drugs and to be thoroughly familiar with their effects in older adults.

• Dosage should generally be substantially lower than for younger patients and it is common to start with about 50% of the adult dose. Some drugs (eg, long-acting antidiabetic drugs such as glibenclamide) should be avoided altogether.

• Review repeat prescriptions regularly. In many patients it may be possible to stop some drugs, provided that clinical progress is monitored. It may be necessary to reduce the dose of some drugs as renal function declines. The Cockcroft and Gault formula (rather than eGFR) is the preferred method for estimating renal function in older adults aged 75 years and over.¹

• Older adults benefit from simple treatment regimens. Only drugs with a clear indication should be prescribed and whenever possible given once or twice daily. In particular, regimens which call for a confusing array of dosage intervals should be avoided.

• Write full instructions on every prescription (including repeat prescriptions) so that containers can be properly labelled with full directions. Avoid imprecisions like ‘as directed’. Child-resistant containers may be unsuitable.

• Instruct patients what to do when drugs run out, and also how to dispose of any that are no longer necessary. Try to prescribe matching quantities.

If these guidelines are followed most older adults will cope adequately with their own medicines. If not then it is essential to enrol the help of a third party, usually a relative or a friend.

Dr Mary Lowth is an author or the original author of this leaflet.