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In the aging population, how does absorption change?

Doesn't change


How does the peak serum concentration change in the older population?

Peak serum conc. may be lower and delayed

Exception: Drugs with extensive first-pass effect may increase because less drug is extracted by the liver which is smaller with reduced blood flow


What are the three factors that affect absorption?


  • Route of admin
  • Concurrent drugs
  • Comorbid illness


What are the effects of aging on volume of distribution?

  • Decreased body water - Lower VD for hydrophilic drugs
  • Decreased lead body mass - Lower VD for drugs that bind to muscle
  • Increased fat stores - Higher VD for lipophilic drugs
  • Decreased plasma protein - higher percentage of drug that is unbound


Factors causing decreased liver metabolism?


  • Aging decreases liver bloodflow, size, mass


What drugs based on metabolism are preferred in older patients? Why?

Phase II (conversion drugs to inactive metabolites) because active metabolites can be dangerous


Why are benzos highly contraindicated in elderly patients?

Benzos have highly active metabolites!


What common drug metabolized through hepatic metabolism should be avoided if possible?



What organ eliminates most drugs from the body?



Why can kidney failure be problematic when dosing drugs?

Reduced kidney fuction = reduced elimination = drug accumulation and toxicity


General effects of aging on the kidney


  • Decreased kidney size
  • Decreased renal blood flow
  • Decreased number of functioning nephrons
  • Decreased renal tubular secretion

And therefore decreased GFR


What changes in serum creatinine occur with aging?

Lean body mass decreases resulting in lower creatinine production, BUT, GFR decreases too resulting in Cr in normal range


What is the usual method to measure Cr clearance?

Estimate using the Cockroft and Gault equation


What are pharmacodynamics?

Time course and intensity of pharmacologic effect of a drug


What are the four goals of a successful drug diagnosis?


  • Use the correct drug
  • Prescribe correct dosage
  • Target correct condition
  • Drug is appropriate for patient


What medications are most commonly associated with adverse drug interactions?


  • Cardiovascular meds
  • CNS
  • Musculoskeletal
  • Meds with narrow margin of saftey


What are the RFs for ADEs?


  • 6 or more concurrent chronic conditions
  • 12 or more doses of drugs/day
  • 9 or more medications
  • Prior adverse drug rxn
  • Low body weight/BMI
  • > 85 yo
  • Cr clearance < 50 mL/min


What is the ADE prescribing cascade?

Prescribing a drug and then prescribing another drug to Tx the previous drug's SEs


Factors that increase risk of drug-drug interactions?


  • Increased number of meds
  • Multiple prescribers
  • Multiple pharmacies


What are some key facts about drug drug interaction?


  • Absorption can be up or down
  • Drugs with similar/opposite effects can have exaggerated/diminished effects
  • Metabolism may be inhibited/induced
  • Herbal preparations can fuck things up


What are the most common adverse effects of drug-drug interaction?


  • Cognitive impairment
  • Confusion
  • Arterial hTN
  • ARF


What are common drug-disease interactions?


  • Obesity alters VD of lipophilic drugs
  • Ascites alters VD of hydrophilic drugs
  • Dementia may increase sensitivity, induce paradoxical rxns to drugs with CNS or antiCh activity
  • Renal or hepatic impairment may impair detox and excretion of drugs


What is the basic principle for dosing drugs?

Start low and go slow. Don't start two drugs at once.