pharmocotherapy Flashcards
1
Q
why is geriatric pharmacotherapy is challenging
A
- more drugs are available each year
- FDA and off-label indications are expanding (BEER’s CRITERIA)
- formularies change frequently
- knowledge of drug-drug interactions advances
- drugs change from prescription to OTC
- Nutraceuticals (herbal preparations, nutritional supplements) are booming
2
Q
Describe aging and absorption
A
- amount absorbed (BIOAVAILABILITY) is not changed
- peak serum concentrations may be lower and delayed
- EXCEPTIONS: DRUGS with extensive FIRST-PASS affect (bioavailability may increase and serum concentrations may be higher because less drug is extracted by the liver, which is smaller with reduced blood flow)
3
Q
what are factors that affect drug absorption
A
- route of administration
- what is taken with the drug
- comorbid illnesses
- divalent cations can affect absopriton of many fluoroquinolones
- enteral feedings interfere with absopriton of some drugs
- INCREASED GASTRIC pH may INCREASE OR DECREASE absorption of drugs
4
Q
Effects of aging on volume distribtion
A
- age-associated changes in body composition can alter drug distribution
- DECREASED BODY WATER –> lower VD for hydrophilic drugs
- Decreased Lean body mass –> lower VD for drugs that bind to muscles
- INCREASED FAT STORES –> higher VD for lipophilic drugs
- DECREASED plasma protein (albumin) –> higher percentage of drug that is UNBOUND (active)
5
Q
Metabolic Clearance of aging and metabolism
A
- METABOLIC CLEARANCE OF A DRUG BY THE LIVER MAY BE REDUCED BECAUSE:
- -> aging decreases liver blood flow, size and mass
- -> the liver is the most common site of DRUG METABOLISM
6
Q
What are some other factors that affect drug metabolism
A
- Age and gender
- Hepatic congestion from heart failure (reduces metabolism of warfarin)
- Smoking (increases clearance of theophylline)
7
Q
What are key concepts about drugs elimination
A
- HALF LIFE = time for serum concentration of drug to decline by 50%
- CLEARANCE = volume of serum from which the drug is removed per unit of time
8
Q
kidney function
A
- Most drugs EXIT the body via the kidney
- Reduced elimination –> drugs accumulation and toxicity
- aging and common geriatric disorders can impair kidney function
9
Q
what are the affects of aging on the kidney
A
- Decreased kidney size
- decreased blood flow
- decreased number of functioning nephrons
- Decreased renal tubular secretion
- LOWER GLOMERULAR FILTRATION RATE**
10
Q
Two ways to determine creatinine clearance
A
- MEASURE
- -> time-consuming
- -> requires 24 hour urine collection
- -> 8 hour collection may be accurate but not widely accepted
- ESTIMATE
- -> usually done with COCKROFT GAULT EQUATION
11
Q
Cockroft-gault equation (BOARDS but not for test)
A
[(IDEAL WEIGHT IN KG)(140 - AGE)] / [(72*Serum creatinine in mg/dL)]
** MULTIPLE BY .85 IF FEMALE**
12
Q
Pharmacodynamics
A
- Time course and intensity of the pharmacologic effect of a drug
- MAY CHANGE WITH AGING, for example
- -> benzodiazepines may cause more sedation and poorer psychomotor performance in older adults (likely cause: reduced clearance of the drug and resultant higher plasma levels)
- -> older patients may experience longer pain relief with morphine
13
Q
Successful pharmacotherapy
A
- uses the correct drug (drug that the hospital uses)
- prescribe the correct dosage
- targets the correct condition
- is appropriate for the patient
- FAILURE IN ANY ONE OF THESE CAN RESULT IN ADVERSE DRUG EVENTS (ADE’s)
14
Q
Burden of injuries from medications
A
- adverse drug events responsible for 5 to 28% of acute geriatric hospitals admissions
- Incidence of ADEs in hospitals: 26/1000 beds
- ADE’s occur in 35% of community dwelling older adults
15
Q
Medications commonly involved in ADEs
A
- cardiovascular drugs, diuretics, NSAIDS (BIG WORRY), hypoglycemics and anticoagulants
- medications with a narrow margin of safety
16
Q
Optimizing prescribing
A
- Achieve balance between over- and under prescribing of beneficial therapies
- 20% of ambulatory older adults receive at least one potentially inappropriate medication
- Nearly 4% of office visits and 10% of hospital admission result in prescription of medications classified as never or rarely appropriate
- Medications intended as primary or secondary prevention
- Aggressive treatment of chronic conditions
17
Q
BEERS CRITERIA
A
- intend to improve drug selection and reduce exposure to potentially inappropriate medications in older adults
- recommendations are evidence-based and in 3 categories: drugs to avoid, drugs to avoid in patients with specific diseases or syndromes, drugs to use with caution.
18
Q
commonly UNDERprescribed drugs
A
- ACE inhibitors for patients with diabetes and proteinuria
- angiotension-receptor blockers
- anticoagulants
- antihypertensives and diuretics for uncontrolled hypertension
- Beta-blockers for patients after MI or with heart failure (can cause depression)
- bronchodilators
- proton-pump inhibitors or misoprostol for GI protection from NSAIDs
- statins
- vitamin D and calcium for patients with or at risk of osteoporosis
19
Q
describe cytochrome P-450 and drug interactions
A
- effects of aging and clinical implications are still being researched
- CYP3A4 is involved in more than 50% of drugs on market
- CYP3A4 is:
- -> induced by rifampin, phenytoin and carbamazepine
- -> inhibited by macrolide antibiotics
20
Q
what are some common adverse effects of drug-drug interactions
A
- confusion/delirium
- cognitive impairement
- hypotension
- acute renal failure
21
Q
principles of prescribing for older patients
A
- start with LOW DOSE
- TITRATE UPWARD SLOWLY, as tolerated by the patient
- AVOID STARTING 2 drugs at the same time
- ask patient to brin in all medications for review (supplements etc)
- ask about side effects and screen for drug and disease interactions
- look for duplicate therapies or pharmacologic effect
- eliminate unnecessary medications
22
Q
Nonadherence
A
- may be as high as 50%
- may result from clinicians failure to consider patients financial, cognitive, functional status
- may result from patients beliefs and understanding of drugs and diseases
