Prescribing in the elderly e-book

Question 1

Factors responsible for adverse drug reactions (ADRs)

Answer 1

 Multiple disease states
 Increased use of medication
 Over prescribing
 Changes in sensitivity to certain drugs
 Alterations in drug handling

Question 2

There are three main reasons for pharmacodynamic changes in the handling of drugs in elderly patients.

Answer 2

1. As the body ages, the number of drug receptors decreases and / or their affinity for the drug molecule alters.
2. Homeostasis changes and conditions such as postural hypotension become more prevalent, resulting in the need to reduce doses of antihypertensive drugs.
3. Elderly patients are also more susceptible to confusion and so drugs that produce confusion as a side effect are much more likely to do so in this group of patients

Question 3

There are several factors that may alter drug absorption in the elderly patient namely:

Answer 3

 reduced saliva production (which may affect the absorption of solid buccal preparations),
 increased gastric pH,
 delayed gastric emptying,
 decreased GI motility,
 decreased GI and regional blood supply.

Question 4

Altered drug distribution

Answer 4

Elderly patients typically have an increased mass of adipose tissue (between 14 and 35%).
This in turn increases the volume of distribution (Vd) of lipid soluble drugs. Conversely, there is a decrease in lean muscle mass by between 12% and 19% which means that drugs, such as digoxin, are less likely to enter the muscle compartment and be stored. This results in more digoxin present in the serum and a need to reduce the dose. There is a decrease in total body water which correspondingly decreases the Vd of water soluble drugs. There are reduced serum albumin levels (although these remain in the normal range on blood testing) as liver function naturally decreases which means that drugs which are extensively bound to albumin (e.g. phenytoin, warfarin and diazepam) are now free to exert more of an effect necessitating a reduced dose.

Question 5

Altered hepatic function

Answer 5

Along with a reduction in the production of albumin, there are two other liver related factors that alter the way drugs are handled by the body. Firstly there is a reduced hepatic
blood flow which in turn results in reduced first pass metabolism of drugs. If drugs are extensively affected by first pass metabolism there may be a corresponding greater drug effect (e.g. morphine, nifedipine). If prodrugs (e.g. many of the ACE inhibitors) are used then the overall drug effect may be reduced. Secondly there is reduced metabolic clearance which can result in accumulation of drugs extensively metabolised by the liver and also
prolongation of the duration of action of such drugs. The cytochrome p450 pathway, for example, is reduced. However, the conjugation pathway is not. Therefore a blanket recommendation to reduce doses of drugs which are extensively metabolised by the liver is not required; generally liver function in terms of metabolism is only slightly impaired in elderly people. A detailed knowledge of how individual drugs are metabolised is required in
order to make appropriate dosing recommendations.
Liver function tests are of little use in predicting deterioration in metabolic function as these only detect liver damage, not ageing. Therefore each patient should be considered in terms of their response to a particular drug and therapeutic drug monitoring may be required.

Question 6

Altered renal function

Answer 6

As a person gets older, the size of their kidneys decreases. This means a loss of functioning glomeruli leading to a decreased GFR. This in turn may result in accumulation of renally excreted drugs (i.e. the half life is increased) and also an increased risk of renal disease or drug induced renal damage.
Drug excretion is both measurable and predictable. Approximately two thirds of people aged over 70 years have a renal function half that of a young adult. Blanket
recommendations about dose reductions for drugs which are renally excreted can therefore
safely be made.

Question 7

Appropriate polypharmacy

Answer 7

‘prescribing for an individual for complex conditions or for
multiple conditions in circumstances where medicines use has been optimised and where the medicines are prescribed according to best evidence.’

Question 8

Problematic polypharmacy

Answer 8

‘the prescribing of multiple medicines inappropriately, or where the intended benefit of the medicines are not realised.’

Question 9

There are many problems associated with polypharmacy in elderly patients:

Answer 9

1. The risk of adverse drug reactions is greatly increased with the number of medicines used
2. The risk of drug-drug interactions is greatly increased with the number of medicines used
3. Chronic conditions may be exacerbated by medicines prescribed for other medical conditions
4. Medicines adherence may decrease as elderly patients may find complex medicine regimens difficult to remember to take as prescribed
5. Patients may become socially restricted as they try to structure their normal daily activities around a complex medication regimen
6. Older patients who cannot adhere to their drug regimen may require support from outside carers or, in extreme circumstances, may require residential care
7. Drug cost and wastage

Question 10

There are many ways in which pharmacists can become involved in medicines optimisation
for elderly patients. These include:

Answer 10

1. Supporting patient adherence with practical measures
2. Managing polypharmacy using various screening tools
   E.g. The Screening tool of older people’s prescriptions (STOPP) and the Screening tool to alert to right treatment (START).
3. Medication review
4. Medicines reconciliation
   a. Medicines reconciliation should be carried out by a pharmacist, pharmacy technician, nurse or doctor – someone who has the necessary skills and knowledge
   b. In the acute setting, medicines reconciliation should take place within 24 hours of admission or transfer
   c. In the primary care setting, medicines reconciliation should take place as soon as possible after discharge from hospital or other care setting and before a prescription is issued
5. Medicines use reviews (MURs)
   a. Key community pharmacy service
   b. 70% of all MURs must take place in four national target groups:
   i. High risk medicines (e.g. NSAIDs, anticoagulants)
   ii. Patients with a high cardiovascular risk
   iii. Patients with chronic respiratory disease
   iv. Post-discharge from secondary care (i.e. patients whose medication
   may have been changed whilst in hospital)

Question 11

key principles within an MUR are

Answer 11

For each drug:

1. Why has it been prescribed?
2. Is it appropriate?
3. Is it still required?
4. Are the dose and frequency appropriate?
5. Is the patient experiencing any side effects?
6. Is it still working?
7. Are there any interactions of clinical significance (don’t forget to consider nonprescription medications too)
8. Can the patient manage the dosage form?