Pharmacology in the Elderly

Pharmacological Challenges in the Elderly  Pharmacokinetic changes  Pharmacodynamic changes  Multiple co-morbidities  Polypharmacy  More adverse effects  Adherence problems/cognition  Reduced diagnostic precision  Few well designed trials in this population

Pharmacokinetics in the Elderly  Absorption: remains relatively unchanged with age  Distribution: reduce in body water increase in body fat plasma protein binding  Metabolism: reduced hepatic blood flow reduced liver volume reduced enzymatic activity  Excretion: reduced renal blood flow atrophic renal tissue

Pharmacodynamic Changes  Changes in drug receptors/target organ responses - alter sensitivity to effect of drugs (> CNS effects of benzodiazepines) 2 nd to neuronal loss  Impairment of secondary compensatory mechanisms - predispose to adverse effects (orthostatic hypotension with diuretics or TCAs).

Co-morbidities  Lead to polypharmacy  Increased risk of developing adverse events 2 nd to co-morbidities  Risk of delirium 2 nd to anticholinergic drugs 2 nd to degeneration of cholinergic pathways  Increased risk of cerebrovascular events on some antipsychotics in people with pre- existing cerebrovascular damage (Shah and Shu, 2005)

Polypharmacy  Over age 65 people use an average of 8 drugs  1/3 of those has inappropriate use of at least one drug  10% are likely to have dangerous drug interaction (Cannon et al., 2006)

Minimising adverse effects  whenever possible, use non-pharmacological treatments  Start low, increase slowly, monitor frequently  smallest number of medications/simplest dose regimens  be familiar with drug effects in elderly  Alternative applications if difficulties swallowing tablets

Minimizing adverse events cont’d  Simple verbal/written instructions for every medication incl. generic/brand names, dosage, frequency, route and indication to avoid confusion  presenting symptoms may be a result of medications (not old age)  Avoid child-proof containers (also elder proof), use Webster pack or RDNS  Ensure carer understands treatment

Reference  Cannon, K.T., Choi, M.M., Zuniga, M.A. (2006), Potentially inappropriate use in elderly patients receiving home health care: a retrospective data analysis. American Journal of Geriatric Pharmacotherapy, 4(2),  Shah, A., Shu, G.H., (2005). A case for judicious use of risperidone and olanzapine in BPSD. International Psychogeriatrics, 17(1),