Table 84 The get up and go test A brief test of postural competence

1. Get up from chair without use of arms.

2. Observe normal gait and 360° turn.

3. Carry out the Romberg test (slight push with eyes closed).

4. Observe tandem walking (heel toe, straight line).

Adverse drug reactions

Ageing is associated with increased rates of adverse drug reactions. 1 The rate of adverse drug reactions for a single medication rises from about 6% at age 20 years to about 20% at age 70 years.

For less than six medications taken concurrently the rate of adverse drug reactions is about 6%. For greater than six medications taken concurrently the rate of adverse drug reactions jumps to 20%. 1

Factors predisposing to adverse drug reactions in the elderly 1

Most adverse drug reactions in the elderly are entirely predictable. Most are merely an extension of the pharmacological action of the drug, e.g. all antihypertensives will reduce blood pressure and have the capacity to cause hypotension and falls in a person with impaired baroreceptor function or poor homeostasis in their vascular tree. Very few adverse reactions are idiosyncratic or unexpected. The five mechanisms of adverse drug reactions in the elderly are:

1. Drug-drug interaction e.g. beta-blockers given concomitantly with digoxin increases the risk of heart block and bradycardia. Alcohol used in combination with antidepressants increases the risk of sedation.

2. Drug-disease interaction e.g. in the presence of renal impairment, tetracyclines carry an increased risk of renal deterioration.

3. Age-related changes leading to increases in drug plasma concentration

Decreased renal excretion can extend the half-life of medication, leading to accumulation and toxicity.

4. Age-related changes leading to increased drug sensitivity e.g. there is some suggestion that the pharmacological response to warfarin, narcotics and benzodiazepines is increased in the elderly. Conversely the pharmacological response to insulin, theophylline and beta adrenergic blocking agents is thought to be decreased.

5. Patient error

Multiple medications can lead to patient error. The incidence and prevalence of dementia also increases with age.

Increasing the number of simultaneous medications increases the risk for all five mechanisms of adverse drug reactions.

In a study on adverse drug reaction in elderly patients the drugs most frequently causing admission to hospital were: 11

• antihypertensives (including beta-blockers)

• psychotropics and hypnotics

• analgesics and NSAIDs

The same study showed that drugs regularly prescribed without revision were:

• barbiturates

• benzodiazepines

• antidepressants

• antihypertensives

• beta-blockers

Drug regimens should be kept as simple as possible to aid compliance and avoid or minimise drug interactions. The elderly may need much lower doses of anxiolytics and hypnotics than younger patients to produce the same effect, thus rendering them more susceptible to adverse effects and toxicity. The elderly are especially liable to accumulate the longer-acting benzodiazepines.

In particular, any drug or combination of drugs with anticholinergic properties, e.g. tricyclic antidepressants, antiparkinsonian agents, antihistamines, phenothiazines and some cold remedies, can precipitate a central anticholinergic syndrome. 8

Starting medications 8

The starting dose of a drug in the aged 8 should be at the lower end of recommended ranges. Dosage increments should be gradual and reviewed regularly.

That is, start low, go slow and monitor frequently. It is important to individualise doses for the elderly.

References

1. Harris E. Prescribing for the ageing population. Update Course Proceedings Handbook, Melbourne: Monash University Medical School, 1992.

2. Sloane PD, Slatt LM, Baker RM. Essentials of family medicine. Baltimore: Williams and Wilkins, 1988, 4956.

3. Mold JW. Principles of geriatric care. American Health Consultants. Primary care reports. 1996, 2(1):2-9.

4. Lang D. Home visits to the elderly. Aust Fam Physician, 1993; 22:264.

5. Ellard J. How to irritate and confuse your elderly patients—20 simple rules. Mod Med Aust, 1990; 7:66-68.

6. McLean S. Is it dementia? Aust Fam Physician, 1992; 21:1762-1776.

7. Turnbull JM. Dementia and depression in the elderly. California: AUDIO DIGEST family practice, 1993; 41:10.

8. Mashford ML (Chairman). Psychotropic drug guidelines (3rd edn). Victorian Medical Postgraduate Foundation, 1996-97, 77-79.

9. Hindmarsh JJ, Estes H. Falls in older persons: Causes and intervention. Arch Int Med, 1989; 149: 2217.

10. Quail GG. An approach to the assessment of falls in the elderly. Aust Fam Physician, 1994; 23:873-883.

11. Briant RH. Medication problems of old age. Patient Management, 1988; 5:27-31.

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