Pharmacology of Old Age Flashcards
What is meant by Pharmacokinetics?
The movement of a drug through the body
What are the principles of pharmacokinetics?
Absorption
Distribution
Metabolism
Excretion
Which is the most important principle of pharmacokinetics?
Metabolism, as the way young people and the elderly metabolise substances differs.
Is age the sole factor for creating changes in medications?
No, must consider other factors too e.g. comorbidities which have to be comanaged.
What are the 2 principles of absorption?
- Basic environments absorb basic drugs e.g. diazepam, morphine
- Acidic environments absorb acidic drugs e.g. aspirin
Which drugs decrease stomach acidity and therefore, acidic drug absorption?
PPIs
H2 Receptor Antagonists
What happens to body pH with increasing age?
Decreases, so the body environment becomes more acidic and cannot absorb basic drugs as well
What happens to the bowels with increasing age?
Decreases in surface area, slowing drug absorption
What is meant by drug distribution?
The proportion of free drug vs. drug bound to protein
What are the principles distribution?
Basic proteins e.g. Albumin, carry acidic drugs
Acidic proteins e.g. Alpha 1 Acid Glycoprotein, carry basic drugs
What happens to carrier proteins with increasing age?
Albumin levels decrease and alpha 1 acid glycoprotein levels increase meaning that basic drug remains unabsorbed in the body longer, increasing risk of delirium or confusion.
What is meant by the volume of distribution (VoD)?
Theoretical volume which will contain the total amount of the administered drug at the same concentration as that of blood plasma
What happens to the proportion of fat and muscle tissue in elderly people?
What does this mean?
Greater proportion of fat tissue to muscle mass.
This means that lipophilic drugs will have a higher VoD as it will be contained within the increased fatty tissue.
In elderly patients, what does the VoD of a drug help to show in terms of drug characteristics?
The lipid solubility and half-life.
The higher the VoD, the higher the lipid solubility and the longer the half-life.
What is the half-life of a drug directly proportional to?
The VoD of the drug
What is the half-life of a drug inversely proportional to?
The hepatic/renal clearance
Why is hepatic metabolism slowed with increasing age?
Decreased liver size
Illness
Decreased hepatic blood flow
Why is renal metabolism slowed with increasing age?
Decreased kidney sizes.
Reduced GFR
Reduced tubular secretion
Reduced renal blood flow
What is the problem with lipophilic drugs in the elderly?
If the patient undergoes cachexia, fatty tissues will break down, releasing the lipophilic protein into the body, resulting in potential delirium or confusion.
Are hydrophilic drugs well-absorbed in the elderly?
Not as well as lipophilic drugs due to age-related loss of water content in the body.
What are bio-transforming enzymes?
Do they increase/decrease with age?
Proteins which alter a substance.
Decrease with age.
What is meant by pharmacodynamics?
How the body responds to a drug?
What is the general principle of pharmacodynamics in the elderly?
A lower dose of the drug will have the SAME effect as normal dosage in a young person
What happens to the therapeutic window with increasing age? What does this mean?
Therapeutic window narrows with age.
This means that toxic responses to drugs increases while therapeutic responses decrease.
How is the therapeutic index of a drug calculated?
Minimum toxic dose/Minimum effective dose
Which drugs have a low therapeutic index (<2)?
- Warfarin
- Digoxin
- Lithium
- Benzodiazepines
Give an example of prophylaxis for an adverse drug effect:
Laxatives for opioid-induced constipation
Vitamin D/Calcium for steroid-induced osteoporosis
Regular blood glucose check for steroid-induced diabetes
Give an example of adverse drug reactions that result from drug interactions:
Calcium slowing down Levothyroxine absorption (therefore, take levothyroxine in the morning and calcium in the evening)
Beta blockers with Verapamil/Diltiazem causing bradycardia
What is important to remember with antibiotics in the elderly?
They must be targeted and given in cases of definite infection.
(due to increased risk of resistance, C.Diff and renal impairment)
What are adverse effects of NSAIDs?
Renal impairment
GI bleed
Reduced diuretic effect due to increased sodium reabsorption
What can be done to as prophylaxis for NSAID adverse effects?
Prescribe paracetamol for patients with mild, non-OA pain
Use less potent NSAIDs in patients with CVD e.g. Ibuprofen instead of Diclofenac
What are adverse effects of opiates?
Psychomotor impairment
Falls
Delirium
Confusion
Why is polypharmacy important?
Patients more likely to suffer from adverse drug effects as multiple drugs means increased risk of interactions
Why are over-the-counter medications important?
They can interact with prescribed medications
What can be done to counteract issues in polypharmacy?
Prescribe 1 drug that can target 1+ problems
Use combination treatments to ease pill burden
Do NOT counter the adverse effect of one drug by prescribing another drug - reduce dose of initial drug or choose alternative
Which screening tools can be used to avoid certain medications in the elderly but alert to appropriate ones?
BEER Criteria (American Geriatric Society) STOP START Tool
