Pharmacotherapy Flashcards
What are key issues and challenges in geriatric pharmacotherapy
more drugs are available each year FDA and off label indications are expanding formularies change frequently multiple providers prescribe meds knowledge of med advances drugs change from Rx to OTC status use of nutraceuticals and increasing effects of aging physiology on drug therapy
What is polypharmacy
the use of multiple medications (>5)
the more drugs, the higher the risk of ADEs/hospitalization
What is the “prescribing cascade”
When ADE are misinterpreted as new medical condition, causing even more meds to be Rx
What are pharmacokinetics
How a drug moves through the body
Absorption, Distribution, Metabolism, Excretion
What are pharmacodynamics
The effects a drug has on the body
In Absorption, the GI tract relies heavily on
passive diffusion
with age: decreased gastric acid secretion= delayed gastric emptying (slower/decreased, but still complete)
What is “time of peak concentration”
time for a drug to reach it’s peak, usually in hours
helps estimate rate of absorption
ex: digoxin peak in 38 hrs in young, 69 hours in old
What age related changes occur in topical absorption
epidermis thins and subQ fat decreases= INCREASED absorption
What is Vd
volume of distribution; ratio of dose present in body and it’s concentration
how is volume of distribution affected
Decreased body water= lower Vd (if hydrophilic)= higher serum level of drug
Dec. LBM= lower Vd for muscle binding drugs
Increased fat stores: higher Vd (if lipophilic)= prolonged half life
Dec. plasma protein (albumin)= more unbound and active
What is the MC site of drug metabolism
LIVER; rate of clearance may be reduced 2/2 aging (decreases liver blood flow, enzyme activity, and mass
What is the Phase I pathway of metabolism
Drugs are converted to active metabolites (CYP450, CYP3A4)
This pathway is the most affected by age (decreases in elderly)
Where are most drugs excreted
KIDNEY!
can be affected by aging and common geriatric d/o
if elimination is reduced, drugs accumulate and can cause toxicity
CHF (common geriatric d/o) is associated with
hypoperfusion to the liver and kidneys
reduced Vd
impaired clearance
increased plasma concentration of drugs
What are the effects of aging on the kidneys
Decrease size Decrease renal plasma flow Decrease renal tubular secretion Decrease # of functioning nephrons (glomeruli) =LOW GFR, even if w/o kidney disease
What is half life
time for serum concentration of drug to decline by 50%
What is clearance
volume of serum from which drug is removed per unit of time
What are the stages of kidney disease, based on GFR
1: 90+
2: 60-89
3: 30-59
4: 15-29
5: <15
Is dig a first line for AFib or HF?
NO! “avoid as first line therapy”
dose based on LBM and renal fxn
MC meds involved in ADEs are
CV drugs Diuretics NSAIDs Hypoglycemics Anticoags Meds with narrow margin of safety
What are some predictors of ADE
6+ concurrent conditions 9+ meds 12+ doses of drugs/day prior ADE Low body weight/BMI 85+ EGFR <50
How do you select the proper drug
Based on effectiveness, safety, convenience, and cost
Why ask yourself “is each med necessary?”
They can be on 4 drugs, and two can be doing the same thing. This way, you can eliminate one drug!
*Dont assume a drug is indicated because it has been prescribed- always monitor for over/under prescribing
Commonly UNDERprescribed drugs include
ACE-I (for DM) ARB Anticoags Anti-HTN/diuretics BB (for HF/ s/p MI) Bronchodilators PPI/misoprostol (to protect from NSAIDS) Statins Vitamin D/Calcium
