Principles of Drug Use in the Elderly Alastair Stephens Sophie Rozwadowski

What is polypharmacy? Taking ≥4 medicines What percentage of the elderly are on polypharmacy? 36% – Up to 50% of older patients do not take their prescribed medicines

What are Adverse Drug Reactions (ADRs)? Undesirable effects of a drug beyond its anticipated therapeutic effects occurring during clinical use – Much more common in elderly patients What factors contribute to ADRs? Dose Time course Susceptibility DoTS classification

What are the Dose-related ADRs? Toxic reaction o Above the therapeutic range Collateral reaction o Within the therapeutic range Hyper-susceptibility reaction o Below the therapeutic range Therapeutic Range 0.5mg1.0mg1.5mg2.0mg Collateral reaction Hyper-susceptibility reaction Toxic reaction

What are the Time course-related ADRs? First dose reaction Early reaction Intermediate reaction Late reaction Withdrawal reaction Delayed reaction 0 1 month 2 months 3 months Drug stopped Late Early Intermediate Withdrawal Delayed First dose

What are the Susceptibility related ADRs? Genetic susceptibility Age Sex Specific physiological states o Pregnancy Diseases o Hepatic impairment o Renal impairment Exogenous factors o Drug interactions o Diet

What is the difference between pharmacokinetics and pharmacodynamics? Pharmacokinetics: how the body affects a drug Pharmacodynamics: how a drug affects the body

What are the 4 pharmacokinetics processes, and what changes occur in the elderly? Absorption o Swallowing, gastric emptying, intestinal motility and surface area Distribution o Tissue perfusion, plasma proteins and volume distribution Metabolism o Hepatic mass, hepatic blood flow and thyroid function Excretion o GFR

What pharmacodynamic changes occur in the elderly? Changes in receptor sensitivity Changes in receptor number Changes in hormone levels o Menopause Altered action of CVS and CNS drugs

What is the “prescribing cascade”? An adverse drug effect is misinterpreted as a new medical condition so a new drug is prescribed Drug 1Adverse drug reactionDrug 2Adverse drug reaction ACE inhibitorDiarrhoeaDry coughAntibiotics

What are some of the strategies to improve concordance? Simplify – Use once-daily dosing if possible – Try to prescribe medicines to be taken at same time of day – Try to use medications with dual indications – Consider daily dose reminder system Educate – Explain reasons for medication & how to take it – Warn of predictable side effects – Enlist support of family & carers Monitor – Check tablet boxes & use of medications – Monitor requests for prescriptions – Serum monitoring if needed How often should medication reviews be? All patients aged >75 years should have an annual review of their repeat medication Those taking ≥ 4 medicines should be reviewed every 6 months

Drug Use in the Elderly Organ function  (altered physiology) Altered pharmacodynamics Homeostatic functions  Side effects / Adverse drug reactions Multi-morbidityPolypharmacyCompliance  Altered pharmacokinetics

Thanks for listening. Any questions?