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Flashcards in pharmocotherapy Deck (22):
1

why is geriatric pharmacotherapy is challenging

- 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

Describe aging and absorption

- 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

what are factors that affect drug absorption

- 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

Effects of aging on volume distribtion

- 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

Metabolic Clearance of aging and metabolism

- 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

What are some other factors that affect drug metabolism

- Age and gender
- Hepatic congestion from heart failure (reduces metabolism of warfarin)
- Smoking (increases clearance of theophylline)

7

What are key concepts about drugs elimination

- 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

kidney function

- Most drugs EXIT the body via the kidney
- Reduced elimination --> drugs accumulation and toxicity
- aging and common geriatric disorders can impair kidney function

9

what are the affects of aging on the kidney

- Decreased kidney size
- decreased blood flow
- decreased number of functioning nephrons
- Decreased renal tubular secretion
** LOWER GLOMERULAR FILTRATION RATE**

10

Two ways to determine creatinine clearance

- 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

Cockroft-gault equation (BOARDS but not for test)

[(IDEAL WEIGHT IN KG)(140 - AGE)] / [(72*Serum creatinine in mg/dL)]
** MULTIPLE BY .85 IF FEMALE**

12

Pharmacodynamics

- 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

Successful pharmacotherapy

- 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

Burden of injuries from medications

- 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

Medications commonly involved in ADEs

- cardiovascular drugs, diuretics, NSAIDS (BIG WORRY), hypoglycemics and anticoagulants
- medications with a narrow margin of safety

16

Optimizing prescribing

- 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

BEERS CRITERIA

- 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

commonly UNDERprescribed drugs

- 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

describe cytochrome P-450 and drug interactions

- 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

what are some common adverse effects of drug-drug interactions

- confusion/delirium
- cognitive impairement
- hypotension
- acute renal failure

21

principles of prescribing for older patients

- 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

Nonadherence

- 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