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Geriatric Pharmacology: Relevance Clarissa Zaoirov (2009). Includes adults >65 years old. Fastest growing population in US and in the majority of developed nations.
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Geriatric Pharmacology: Relevance Clarissa Zaoirov (2009) Includes adults >65 years old • Fastest growing population in US and in the majority of developed nations. • 20% of hospitalizations for those >65 are due to medications they’re taking = Adverse Drug Events/Interactions are very common in the elderly.
What is different about geriatric pharmacotherapy? • Absorption – Not usually significantly altered with age. Reduced motility and gastric emptying = constipation • Distribution – Change in total body composition, vascular changes, lower albumin production (not always) • Metabolism – Reduced hepatic blood flow & mass, low CYP-450, slow biotransformation (Phase I metabolic pathways) • Excretion = Renal blood flow by age 80, can be reduced by as much as ½. Reduction in tubular function & size.
Pharmacodynamic Changes: • Disturbed homeostatic mechanisms: • - Reduced compensatory tachycardia, baroreceptor and vasomotor response. • - Poor thermoregulatory mechanisms • - Cardiac Beta receptor sensitivity reduced • - Hepatic Beta receptor sensitivity increased • - Greater sensitivity to medications affecting the CNS (benzodiazepines and opioids) • - Pre-existing depletion of dopamine = Parkinsonism when using anti-psychotic medications.
Total Result: • These age-related changes result in greater therapeutic effect and increased risk of accumulation & toxicity. (Longer ½ life) • Complicated by alterations in metabolism, distribution and clearance. • Example: Benzodiazepines may cause more sedation and poorer psychomotor performance in older adults. Likely cause: reduced clearance of the drug and resultant higher plasma levels, wider volume of distribution of lipophylic drug and active metabolites.
Other factors that complicate pharmacotherapy: • Polypharmacy including naturaceuticals. (Ginko biloba) • Non-Compliance Issues • Drug-Disease Interactions • - Anticholinergics Benign. Prostatic Hypertrophy (BPH), constipation, dementia • Antiarrhythmics (Type 1A) CHF (systolic dysfunction) • Amphetamines Hypertension (HTN), insomnia • Aspirin Peptic Ulcer disease (PUD) • Atypical antipsychotics DM (Diabetes Mellitus) • Barbiturates Depression • Benzodiazepines COPD,dementia, falls • Beta-blockers COPD, DM, syncope • CCB 1st generation CHF (systolic dysfunction) • Chlorpromazine Postural hypotension, seizures • Clozapine Seizures • Corticosteroids DM, PUD, COPD • Decongestants Insomnia
Recommendations: • Start low and advance dosage slowly. Avoid the prescription cascade! • Cockcroft-Gualt Formula (Creatinine Clearance) : • Beers Criteria or MAI * • ANY new symptom or disease in an elderly patient should be treated as Adverse Drug Event unless proven otherwise. (i.e.. Dementia) Constantly review medications for appropriateness.