Pharmacotherapy in Older Adults Flashcards
How is absorption affected by aging? Give an example of drugs that have their absorption affected by the presence of divalent cations. Give an example of a drug that has its absorption affected by enteral feedings.
BIOAVAILABILITY IS NOT AFFECTED BY AGING! The exception is that in using a drug with extensive first-pass metabolism, bioavailability may increase if less liver metabolism occurs due to smaller liver with reduced blood flow with aging. Fluorquiolones. Phenytoin.
What are the effects of aging on volume of distribution?
Decreased body water –> Lower Vd for hydrophilic drugs. Decreased lean body mass –> Lower Vd for drugs that bind to muscle. Increased fat stores –> Increased Vd for lipophilic drugs. Decreased plasma proteins (albumin) –> Increased percentage of unbound (active) drug.
How does aging affect metabolism?
Because the liver decreases in size and mass with age and has reduced blood flow with age, the metabolic clearance of a drug by the liver can be reduced with age.
Drugs that follow which metabolic pathway are preferred in older patients? Why? What are examples of drugs that go through the unpreferred pathway?
Phase II drugs are preferred in older patients. This is because phase II pathways convert drugs to inactive metabolites that do not accumulate. Phase I pathways convert drugs to metabolites that may have lesser or the same affect, but may have greater effects. Phase I drugs: Long-acting benzodiazepines (diazepine).
What drug is metabolized faster in older men than women? What drug is metabolized slower in older women versus younger women? Hepatic congestion due to heart failure reduces the metabolism of what drug? Smoking increases the clearance of what drug?
Oxazepam. Nefazodone. Warfarin. Theophylline.
What are the effects of aging on the kidney? How can serum creatinine levels be misleading in regards to creatinine clearance? As such, what is the best way to measure creatinine clearance?
Decreased kidney size, Decreased renal blood flow, Decreased number of functioning nephrons, Decreased renal tubular secretion. END RESULT: DECREASED GFR. In an older adult, there is decreased lean body mass, and thus decreased creatinine production; this, coupled with a decreased GFR, may inappropriately result in what may appear as a normal serum creatinine, thereby masking a change in creatinine clearance. Best ways to measure creatinine clearance: Measure via 24-hr urine collection, Estimate via the Cockgroft-Gault equation = [Weight in kg x 140-age]/[72 x serum cr in mg/dL] x (0.85 if female).
What meds require dose reduction with decreased creatinine clearance?
ACEi, Aminoglycosides, Atenolol, Bisphosphonates, Clofibrate, Digoxin, Fluconazole, Fluorquinolones, Lithium, Metformin, Penicillins, Procainamide, Thiazides.
Give an example two drugs that have their pharmacodynamics affected by aging.
Benzodiazepines: Cause increased sedation & worser psychomotor performance in older adults due to reduced clearance and subsequent higher plasma levels. Morphine: Older patients may experience higher levels with longer pain relief.
What are the most common medications involved in adverse drug events? What are the RFs for ADEs? What are meds with a high potential for severe ADEs? What are meds with a high potential for less severe ADEs?
Most common: Cardiovascular, CNS, MSK. RFs: 6+ chronic conditions, 12+ doses/day, 9+ meds, prior ADE, low body weight of BMI, 85+, estimated CrCl 0.125 mg/day, Disopyramide, GI antispasmodics, Meperidine, Methyldopa, Pentazocine, Ticlopidine. High potential for less severe ADEs: Antihistamines, Diphenyhydramine, Dipyridamole, Ergot, Indomethacin, Meperidine (oral), Muscle relaxants.
What are RFs for drug-drug interactions? What can these lead to?
RFs: Increased number of meds, multiple prescribers, multiple pharmacies, physiologic & pharmacokinetic changes. These can lead to ADEs, most commonly: confusion, cognitive impairment, arterial hypotension, acute renal failure.
Give 6 common drug interaction and associated ADE.
ACEi + diuretic: Hypotension, Hypokalemia. ACEi + K+: Hyperkalemia. Antiarrhthymic + Diuretic: Electrolyte imbalance, arrythmias. Antiarrhthmic + Digoxin: Bradycardia, arrythmias. CCB + Diuretic or Nitrate: Hypotension. Benzodiazepine + Antidepressant, Antipsychotic, or another Benzodiazepine: Confusion, Sedation, Fall.
Based on the Beers Criteria (2012), what drugs should be avoided in the elderly & why?
Benzodiazepines (cognitive effects and injury, such as fall). Megestrol (minimal effect on weight + risk of thrombotic events & death). Metoclopramide (EPS & TD). Non-COX NSAIDs (GI bleeding [can protect with PPIs or misoprostol]). Nitrofurantoin (lack of efficacy + pulmonary toxicity). Antipsychotics (increase CVA & CV mortality in dementia). Sliding scale insulin (hypoglycemia). Chlorpropamide, Glyburide (hypoglycemia).
How does obesity affect VD? What about ascites? How does dementia affect the sensitivity of drugs?
Obesity alters the Vd of lipophilic drugs. Ascites alters the Vd of hydrophilic drugs. Dementia may increase sensitivity of drugs.
