Chapter 9 Geropharmacology Flashcards
Absorption
How the drug is taken into the body
-Bioavailability
-Amount of drug that passes through absorbing surfaces in body
•Some medications are directly absorbed through the stomach
•Most are absorbed in the duodenum
Pharmacokinetics
Study of the movement and actions of a drug in the body
Distribution
Where the drug goes in the body
Metabolism
How the drug is broken down
- Chemical structure of drug is converted to metabolite more easily used and excreted.
- Liver is primary site for metabolism, although many other organs have metabolizing enzymes.
- Genetic differences in drug metabolism can affect serum drug levels and rate of excretion.
- Greater understanding of the human genome can lead to “personalized medicine” tailored to individual metabolism for maximum therapeutic effect.
Excretion
How the drug leaves the body
- Drugs and their metabolites are excreted in sweat, saliva, and other secretions but primarily through kidneys.
- Renal drug excretion occurs when drug is passed through kidney and involves glomerular filtration, active tubular secretion, and passive tubular reabsorption.
- Assessment of creatinine clearance rate an important consideration in older adults to prevent drug toxicity.
Where are most meds absorbed?
Duodenum
Absorption changes with aging: GI motility
Decreased GI motility
- Increased absorption time
- Can lead to increased levels of the medication in the patients system
- NO CONCLUSIVE EVIDENCE TO SUPPORT THIS
- Least effected by the aging process
Absorption changes with aging: Skin
Skin changes with aging
- Underweight and overweight: unreliable dosing
- Thinning, dryness, and roughness of the skin effects absorption
- Allergic reaction risk is increase
- Must be placed on intact skin
- Need to see the clint do it (return demonstration)
Distribution: Lipophilic drugs
- Pass through the capillaries easily
- More rapid and greater volume of distribution
- Stored in fatty tissue
- Older adults have a higher ration of adipose tissue to body mass
Hydrophilic drugs
-Decreased body water: increased serum plasma concentrations
-philic vs -phobic
- philic = like
- phobic = dislike
Plasma Proteins
- Lipoproteins, globulins, and albumin
- Some drugs are bound to proteins for distribution
Problems with protein bound medications
- Meds not bound to protein are free in the plasma and wiill have their therapeutic effect.
- Decreased protein = decreased med-protein binding = higher plasma concentrations.
- Some meds compete with others for protein binding (whichever loses is displaced and their serum concentrations are increased)
- Ill elderly: Decreased serum albumin (malnutrition, acute illness, long-standing chronic condition) = unpredictable amounts of free-drug available.
Decreased protein binding, increased drug effect:
Warfarin
Phenytoin
Increased protein binding, and less drug effect
ASA Lorazepam Diazepam Chlorpromazine Phenobarbitol Haloperidol Lidocain Propanolol
Changes with aging: Metabolism
First Pass metabolism
- Decreased liver mass
- Decreased liver blood flow
- Decreased liver function
- Decreased hepatic exposure