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
Every single vein in the digestive system joins with what vein in the liver?
Portal vein
Drugs that are typically not affected by First-Pass metabolism, and therefore not typically affected by the aging process, include:
antibiotics
Baroreceptor reflex decreases with aging
Anticholinergic drugs: risk with position changes, and risk with volume changes
Increase in Sympathetic Nervous System
Decreased response to Beta blockers
Increased response to diuretic
Polypharmacy
- Taking multiple medications at same time
- Increased risk for drug interactions: Drug-supplement interactions, Drug-food interactions, Drug-drug interactions.
- 20% of older adults take 10 or more drugs (even higher in long term care settings.
- The main problem is lack of communication between healthcare providers.
Most common errors of medication administration via enteral feeding tubes
- Incompatible route
- Improper preparation
- Improper administration
- Always have pharmacist provide liquid form when available
Issues and Trends in Medicine Use: Self-Prescribing of Medicinal Products
- -People of all ages frequently medicate themselves with former prescriptions, prescriptions borrowed from friends, or over-the-counter (OTC) drugs
- -Self-treatment includes purchasing herbal and nutritional supplements, which may be recommended by acquaintances and are thought to be harmless because they are “natural.”
- -Problem is with under-reporting, and patient education
Adverse Drug Events (ADR’s): Most common categories associated with ADR’s
Cardiovascular agents Psychotropics Anticoagulants Diuretics Hypoglycemics Non-opioid analgesics
Antidepressants
- SSRI’s most effective
- Most older adults are sensitive to these, and lower doses need to be considered
- Side effects are manageable and usually resolve with time (dry mouth, sedation, sexual dysfunction)
- SNRI’s have less sexual side effects.
Anxiolytic agents
-Bezodiazepines, and Buspirone
-Many people self-medicate with antihistamines.
Side effects: drowsiness, dizziness, ataxia, mild cognitive impairment, and memory impairment
Signs of Toxicity:
Excessive sedation Unsteady gait Confusion Disorientation Agitation Wandering Cognitive and Memory Impairment
Mood stabilizers
- Lithium, Valporic Acid, Lamictal
- Low salt diet: elevated serum Lithium levels
- Thiazide Diuretics and NSAIDS: elevated serum Lithium levels (ibuprofen)
- Valporic acid: liver functions must be monitored as well as therapeutic levels.
Antipsychotics
- Work by blocking Dopamine receptor pathways in the brain
- Sedation, Hypotension, and Extrapyramidal Side Effects (EPS), and altered thermoregulation
Neuroleptic malignant syndrome
- Altered thermoregulation
- Even slightly higher environmental temperature will raise core body temp and damage liver.
- Cool environment, hydration, avoid direct sunlight.
Acute dystonia
- Slows continuous muscular contractions/spasms
- Starts hours to days after start of treatment or increase in dose.
- Mouth, jaw, face, and neck.
- Eyes may lock up (oculogyric crises), jaw may lock (Trismus), tongue may roll back and block throat, neck may arch backwards.
- Painful and frightening
Akathisia
- Compulsion to be in motion
- Feel restless, and unable to stay still
- “Crawling out of skin”
- May be mistaken for worsening psychosis
Parkinsonian symptoms
- Bilateral Tremor, bradykinesia, rigidity, akinesia, inflexible facial expression
- Often misdiagnosed as depression
- Occur within weeks to months of start of treatment
Tardive dyskinesia
- WILL NEVER GO AWAY
- Tongue thrusting, and twitches or spasms of the face
- Involuntary twisting of limbs, trunk, neck and face
Treatment for Acute Dystonia (not life-threatening
–Anticholinergic Medications: benztropine (Cogentin), trihexiphenidyl (Artane), diphenhydramine (Benadryl) •IM or PO
–Amantadine (Symatrel) •Longer onset of action (not used in acute): Used for prevention •Not very safe for use in elderly
Treatment for Parkinsonian and Akathisia
–Same meds, but effect is less predicible
–Propanolol and Clonidine: Akathisia •Hypotension and sedation can be unsafe in elderly
Treatment for Tardive Dyskinesia
NO TREATMENT
PERMANENT
Issues and Trends in Medication Use: Misuse of Drugs
- Overuse, underuse, erratic use, and contraindicated use
- May occur due to inadequate skills of the nurse or the prescriber, misunderstanding of instructions, or inadequate funds to purchase prescribed medications.
What is the most important factor to include in safe medication use?
EDUCATION
Pearls for gerontological nurses
–Key persons •Who manages the medications •Make sure they are present when teaching is done –Environment •Minimize distractions •Make sure patient is comnfortable (Toileting, Hunger, thirst, etc…) –Timing –Communication •Simple and direct language –Reinforce teaching
