Flashcards in Geriatric Pharmacology Self Study Deck (16):
What are the changes in absorption which occur in aging?
GI oral absorption is largely unchanged, but digestion slows
What are the distribution changes that occur with age? (think of body composition changes) How does this influence halflife?
1. Decreased lean body mass -> increase plasma concentration of water soluble drugs (decreased half life)
2. Increased body fat -> higher Vd for lipophilic drugs (higher halflife)
3. Total body water decreases -> increased plasma concentration of water soluble drugs
4. Decreased serum albumin concentration -> decreased protein binding, can lead to toxicity if extra drug is given
What are the metabolism changes which occur in the liver due to aging?
Decreased phase 1 activity, but phase 2 relatively unaffected
Hepatic size and blood flow is relatively diminished
What happens to renal drug elimination with age, and creatinine levels?
Decreases due to a drop in GFR, scary for aminoglycosides / digoxin with narrow therapeutic window
Creatinine levels -> may stay the same due to drop in lean body mass
What is the Cockroft-Gault equation?
Formula for adjusting drug doses for renal function, based on body weight parameters and creatinine concentration (Age > 75)
Creatinine Clearance = ((140-age) * wt / (Scr * 72))
Multiply by 0.85 only in women
How should the pharmacodynamic changes in elderly patients be handled?
Start low, go slow
Start at low doses, and titrate up slowly while closely monitoring for abnormal response
-> responses to all drugs are increased across the board, except maybe a decreased sensitivity of baroreceptor reflex
What is the Beers criteria?
A list of 53 medications or classes which should be taken into consideration before prescribing to elderly
Can adverse drug reactions be preventable?
Yes, in fact 50% are in the US. 95% are predictable
->most common in polypharmacy
What is an important physical sign / risk factor for falling? What can induce it?
Orthostatic hypertension -> diuretics, nitrates
What other drug class is associated highly with falls?
Psychoactive drugs -> due to confusion, sedation, dizziness, and balance problems
What is double incontinence?
Inability to control both stool and urine at wanted time
What is the "prescribing cascade"?
A drug is given for a side effect of another drug, which causes more side effects
What are the best types of drugs to give to the elderly?
Rapid onset, relatively brief duration, cleared by phase II metabolism
What is inappropriate prescribing vs undertreatment?
Inappropriate prescribing - giving a drug which causes an ADR risk when there are safer alternatives
Undertreatments - failing to treat a druggable condition or prevention of condition
What antibiotic is known to lead to an increase in warfarin activity by displacing it from proteins in plasma?
Sulfonamide antibiotics, like TMP/SMX