Pharmacokinetic and Pharmacodynamic Considerations in the Elderly

Flashcards on Pharmacokinetic and Pharmacodynamic Considerations in the Elderly

Pharmacokinetics

The study of how the body absorbs, distributes, metabolizes, and eliminates drugs.

Pharmacodynamics

The study of the time course and intensity of a drug's pharmacologic effects.

Adverse Drug Event (ADE)

An undesirable experience associated with the use of a medical product in a patient.

Prescribing Cascade

When an adverse drug effect is misinterpreted as a new medical condition, leading to a new medication being prescribed.

Bioavailability

The fraction of an administered dose of unchanged drug that reaches the systemic circulation.

Volume of Distribution (Vd)

A theoretical volume that describes the distribution of a drug in the body.

Clearance (Cl)

The rate at which a drug is removed from the body.

Half-life (t½)

The time it takes for the plasma concentration or the amount of drug in the body to be reduced by 50%.

Glomerular Filtration Rate (GFR)

The rate at which fluid is filtered from the blood into the kidney tubules; a measure of kidney function.

Creatinine Clearance (CrCl)

A measure of the rate at which creatinine is cleared from the blood by the kidneys.

Beers Criteria

A list of medications that are potentially inappropriate for use in older adults.

STOPP Criteria

Screening Tool of Older Persons’ Prescriptions - criteria for potentially inappropriate prescribing in older people.

START Criteria

Screening Tool to Alert doctors to Right Treatment.

Dopa-decarboxylase

Enzyme in the stomach; reduced activity with age increases levodopa bioavailability

Hydrochloric Acid

Gastric secretion; decreased secretion with age can increase gastric pH

GI function

Alterations in this function with age affects drug absorption

First-pass effect

The initial metabolism in the liver of a drug absorbed from the GI tract before the drug reaches systemic circulation.

Therapeutic Endpoints

The desired outcomes of the medication therapy

Social Determinants of Health

Nonmedical factors that impact health outcomes

Activities of Daily Living

(ADLs) – Daily self-care activities within an individual’s place of residence, in outdoor environments, or both

Instrumental Activities of Daily Living

(IADLs) – Complex skills needed to live independently

Passive Diffusion

The process by which most drugs are absorbed in the proximal small bowel

Lean Body Mass

Decreases with age – impacts Vd of drugs that bind to muscle

Serum Albumin

Protein in the blood -- Decreases in hospitalized or poorly nourished patients Increase in unbound fraction of highly protein bound acidic drugs

Alpha-1 Acid Glycoprotein

Protein in the blood -- Increased in older adults Decrease in unbound fraction of highly protein bound basic drugs

Renal Blood Flow

Decreases ~1%/year after age 50

Nephrons

Functional unit of the kidney -- Number decreases with age

Renal Tubular Secretion

Decreases with age

Homeostatic Mechanisms

Age-related impairment alters pharmacodynamic mechanisms

Orthostatic Hypotension

Decrease in blood pressure related to positional or postural changes from lying to sitting or standing positions

Baroreceptor Responsiveness

Decreased with age - Results in orthostatic hypotension

Urinary Incontinence

Involuntary leakage of urine

CNS Depression

Sedation, confusion; can be caused by benzodiazepines

Cholinergic Blockade

Can cause sedation, confusion, and reduced ability to recall

Anticholinergics

Medications with the ability to block acetylcholine which may lead to confusion, cognitive decline, constipation, etc.

Skeletal Muscle Relaxants

Often anticholinergic which should be avoided in elderly

Alpha Blockers

Can cause orthostasis – Beers Criteria for Cardiovascular

Alpha Agonists, Central

Can cause CNS/bradycardia/orthostasis – Beers Criteria for Cardiovascular

Sulfonylureas

Long duration -- Can cause hypoglycemia/SIADH – Beers Criteria for Endocrine

Proton Pump Inhibitors

Can cause C. difficile/bone loss/bone fractures – Beers Criteria for GI -- Avoid use > 8 weeks, unless high-risk patients

Antispasmodics

Should be avoided in elderly – Beers Criteria Anti-infective

Syncope

Temporary loss of consciousness caused by a fall in blood pressure

Delirium

A state of acute mental confusion

Dementia

A chronic or persistent disorder of the mental processes caused by brain disease or injury and marked by memory disorders, personality changes, and impaired reasoning.

SIADH

Syndrome of Inappropriate Antidiuretic Hormone

Hyponatremia

Low sodium level in the blood

ACEI/ARBS

Medications that can result in Hyperkalemia when combined with Trimethoprim/Sulfamethoxazole (Bactrim)

Multiple Anticholinergics

Increased Risk of Falls

Opioids-benzodiazepines

Increase risk overdose

Warfarin-Ciprofloxacin

Increased Risk of Bleeding

Prescription drug use in older adults

60-79 years = ≥1 medication 83.6%

Metabolism

Phase I metabolic Pathways most impacted by aging.

Kidney Size

Decreases with Aging.

Renal Blood Flow

Decreases ~ 1%/year after age 50.

Serum Creatinine

Does not reflect creatinine clearance.

Pharmacodynamics

Time course and intensity of pharmacologic effect of a drug.

Antihypertensives

Decreased baroreceptor responsiveness results in orthostatic hypotension

Nitrofurantoin

Avoid long-term suppression and CrCl less than 30 mL/min.

Gastric Duodenal Ulcers

Non-Cox-2 selective NSAIDs and Aspirin higher than 325mg

BPH

Strong oral anticholinergics except for UI

Hyponatremia

May be caused by Antipsychotics, Diuretics, SSRIs, SNRIs, TCAs, Mirtazapine, Tramadol.

Age Alters Pharmacokinetics

Drug absorption, distribution, metabolism and elimination.

Age Alters Pharmacodynamics

Impairment varies considerably from person to person.

Successful Drug Therapy

Choosing the correct dosage of the correct drug for the condition and individual patient.

ADE

Adverse Drug Events are common among older patients.

Deprescribing

Consider deprescribing when medications are potentially inappropriate or unnecessary.

Low Body Weight

Risk Factors For ADEs

Body Mass Index

Risk Factors For ADEs

Low Dose

Start With These When Prescribing for Older Patients

Titrate Upward Slowly

As tolerated By the Patient

Polypharmacy

Is Common Among Elderly Patients

Drugs-To-Treat Conditions

Could one drug be used to treat 2 conditions/ask before adding

Multiple Medications

Risk factors for Older adults

Cognition Change CNS

Increase sensitivity to Medications

Older Adults

Increased sensitivity to medications CNS

Avoid Starting, Two Drugs

At The Same Time

Warfarin

Monitor Drug Free Levels_With Low Albumin

Adherence to Medication

Decreases with >50% of elderly use 4 or more medications