Special Patient Populations - Geriatrics Flashcards
How is the GI tract different in the elderly?
- higher pH in the GI tract
- increased absorption of basic Rxs and acid labile Rxs
- decreased absorption of acidic Rxs
How is the stomach emptying time different in the elderly?
- delayed stomach emptying time
- delays rate of absorption for most drugs
- may decrease the amount of absorption for some drugs
How does diarrhea and gastroenteritis alter oral drug absorption?
- results in decreased intestinal transit time
How does constipation alter oral drug absorption?
- increased intestinal transit time
How do feeds (milk, enteral feeds) alter oral drug absorption?
- potential for drug interactions
How do less bile salts (gall bladder surgery) alter oral drug absorption?
- diminished bile acid pool and biliary function
- ma decrease absorption of fat soluble drugs and vitamins
How is intramuscular drug absorption different in the elderly?
- less muscle tone and contractions in the elderly
- less muscle oxygen
How does topical drug absorption differ in the elderly?
- thinner skin layer and less skin water (dryer skin)
- hydrated skin increases absorption
What are factors that affect drug distribution in the elderly?
- less total body water content
- less muscle mass (lean body mass)
- more body fat
- less plasma protein binding (decreased serum albumin; hypoalbuminemia due to malnourishment or renal failure)
What are the effects on Vd in the elderly?
- contracted Vd for water soluble drugs
- larger Vd for fat soluble drugs
What are the effects of contracted Vd for water soluble drugs in the elderly?
- higher drug concentrations (may need to reduce the dose)
What are the effects of larger Vd for fat soluble drugs in the elderly?
- tissue drug storage
- prolonged drug effects (i.e., diazepam, haldol)
- lower serum concentrations (but elderly more sensitive to drug effects)
- at increased risk of toxicity if lose weigh and given the same dose
What are the effects on plasma protein binding with changes with hypoalbuminemia?
- increased free drug so may be increased toxicity
- increased drug also excreted so can have a new steady state
What are the immediate and long term effects of a greater free drug fraction?
- immediate effects: increase drug effects and toxicity
- long term effects: increase drug clearance and new steady state concentrations
What are factors to consider in dosing?
- age
- gender
- weight
- ethnic background
- concurrent disease states
- concurrent drug therapy
