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308: Clinical Pharamacology & Therapeutics > Drugs in Health and Disease 2 (Prescribing in elderly) > Flashcards

Drugs in Health and Disease 2 (Prescribing in elderly) Flashcards

1
Q

85 yr old frail female admitted after a fall

DH: Warfarin, Perindopril, Diazepam, Ibuprofen, Furosemide, Sertraline, Amlodipine, Prochorperazine, Betahistine

What problem meds can you identify which may have contributed to the fall or cause problems because of the fall?

A

Warfarin/ibuprofen
- increase bleeding risk from fall

Ibuprofen/furosemide/perindopril
- Acute renal failure

Sertraline
- Low sodium, GI bleeding

Diazepam
- Sedation

Amlodipine
- antihypertensives increase risk of falls

Prochlorperazine
- Parkinsonism

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2
Q

What are pharmacodynamics and pharmacokinetics?

A

Pharmacodynamics- the effect a drug has on the body

Pharmacokinetics- the effect the body has on a drug. Factors: absorption, distribution, metabolism, excretion

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3
Q

How is drug absorption different in the elderly?

A
  • Reduced saliva
  • Reduced gastric acid
  • Decreased GI motility
  • Reduced surface area for absorption
  • Reduced splanchnic blood flow

The overall effect is such that there is reduced absorption and it takes longer for a drug to reach a steady state

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4
Q

How does absorption changes affect levodopa and bisphosphonates?

A
  • Levodopa competes with nutrients. Regimes should avoid meal times
  • Bisphosphonates should be taken on an empty stomach, 30minutes before food
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5
Q

What is volume of distribution?

A
  • Hypothetical volume obtained if all the drug entered blood

Vd= amount of drug in blood/ concentration in plasma

  • if affects half life and duration of effect
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6
Q

How does muscle mass in elderly affect volume of distribution?

A
  • Reduced muscle mass (lean) decreases Vd for drugs that distribute into muscles e.g. digoxin
  • Results in higher plasma concentrations
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7
Q

What are the side effects of digoxin toxicity?

A

Cardiac
- heart block, bradycardia, junctional tachycardia

Psychiatric
- delirium, fatigue, malaise, confusion, dizziness

Visual
- blurred or yellow-green vision, halos, double vision, photophobia

GI
- nausea, vomiting, anorexia, diarrhoea, abdo pain

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8
Q

How does cardiotoxicity in digoxin toxicity vary?

A
  • Patient with normal digoxin levels but renal insufficiency or severe hypokalaemia can have cardiotoxicity more serious than a patient with high levels and no renal/electrolyte disturbance

-

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9
Q

How do you treat digoxin toxicity?

A
  • Withdraw drug
  • Correct electrolytes
  • If severe: digoxin specific antibody fragment (Digibind)
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10
Q

How does fat mass in elderly affect volume of distribution?

A
  • Increased body fat causes increase Vd for fat soluble drugs e.g. benzodiazepines, haloperidol
  • This increases half life
  • e.g. diazepam Vd doubles . This increases its t1/2 from 24 hours (in young patients) to 90 minutes in elderly
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11
Q

A 90 year old patient presents with drowsiness, confusion, ataxia. She has developed a dependence for Diazepam. How would you treat her?

A
  • IV Flumazenil 200mcg
  • Antagonises the effects of benzos
  • It has a shorter half life than diazepam and so patient may become re-sedated
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12
Q

How does body water in elderly affect volume of distribution?

A
  • Body water decreases
  • Decreased Vd of water soluble drugs e.g. gentamicin
  • This increases the plasma concentration of these drugs
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13
Q

How does albumin concentration in elderly affect volume of distribution?

Which drugs are affected?

A
  • Albumin reduction up to 25%: further depressed by HF, renal disease, Rh arthritis, hepatic cirrhosis, malignancy
  • Reduces drug binding capacity
  • Increase free drug

Phenytoin, warfarin, propanolol, diazepam, levothyroxine, digoxin, furosemide

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14
Q

Symptoms of phenytoin toxicity

Why does it occur

A

Hypoalbuminaemia –> increase free drug in blood

  • Nausea, vomiting
  • Tremor, Ataxia
  • Nystagmus
  • Coarse facies
  • Hepatitis
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15
Q

Describe the warfarin-aspirin interaction

A
  • Warfarin is a highly bound to plasma albumin
  • It has a narrow therapeutic window and a small Vd
  • Aspirin can displace warfarin from plasma albumin
  • Displacement of 1-2% of bound warfarin can x2/3 the concentration of free warfarin
  • This increases the bleeding risk
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16
Q

What are the side effects of antiplatelets like aspirin?

How does this compare to anticoagulants such as warfarin/DOAC?

A
  • PUD
  • Bleeding tendency
  • Fluid retention
  • Renal failure

They also have bleeding tendency and they interact with other drugs

17
Q

How is liver metabolism in the elderly different?

Give an example of a drug affected by this change

A
  • The volume of the organ is less
  • less hepatic blood flow
  • FPHM decreases as a result of decreased blood flow
  • Decreased enzyme activity (CP450) which decreased clearance of drugs –> increased t1/2

Antidepressants. antipsychotics, B-blockers, opiates, benzodiazepines, warfarin, phenytoin, NSAIDs, paracetamol, erythromycin

18
Q

How does renal function change in elderly?

A
  • Renal mass and renal blood flow decrease
  • 30% nephron loss so function decreases
  • GFR declines 1% per year after 40
19
Q

How is renal excretion in the elderly different?

Give an example of a drug affected by this change

What are the therapetic indications?

A
  • Reduction in renal function increases t1/2 of drugs and their serum levels

Drugs excreted primarily by kidneys
- digoxin, atenolol, sotalol, lithium, allopurinol, many antibiotics

Reduce dose in OD preparations, increase dosage interval in more frequently administered drugs

20
Q

At which plasma level does lithium toxicity begin?

What are the signs of lithium toxicity?

A 
Li >1.5mmol/l
- tremor, agitation, twitching
- lethargy
>2mmol/l
- coma, fits, arrhythmia, renal failure (haemodialysis may be needed)
21
Q

A patient has been started on s/c morphine for pain management. She has been vomiting and feels drowsy

O/E: 110/50
Investigations: Low eGFR

What is this?
Why has this happened?
What other symptoms of this syndrome might you see?
How would you treat her

A

Morphine undergoes phase 2 metabolism by conjugation. The metabolite (morphine-6-glucoronide) is 40x more potent. It is the metabolite which is responsible for the analgesic effects.

Her renal impairment has caused an accumulation of the active metabolite –> morphine toxicity
- further exacerbated by the fact it was given sc (2x more potent that PO)

IV Naloxone 400mcg

22
Q

State the effects of the following drugs which are increased in elderly

(1) Alcohol
(2) Benzodiazepines
(3) Warfarin
(4) Hypotensives
(5) NSAIDs
(6) Anticholinergerics

A
  1. Drowsiness, lateral sway
  2. enhanced sedation
  3. Anticoagulatory effects increased
  4. Effects increase, postural hypotension
  5. GI effects
  6. Central effects: delirium, confusion
23
Q

State three effects that are decreased in the elderly

A
  • The effect of B1 modulators in cardiac tissue
  • Reduced and delayed bronchodilatory response to B-agonists
  • Calcium channel blocking effect on PR interval
24
Q

An elderly patient has difficulties swallowing her tablets

What advice can you give her?
What is she at risk at?

A
  • Take medications with lots of fluid
  • Sit in upright position
  • Consider a liquid preparation for patient

If left in mouth, ulceration may occur

25
Q

Consider the antihypertensives

What are the side effects of ACE inhibitors?

Give an example

A
  • Hypotension
  • Potassium sparing (can cause hyperkalaemia)
  • Renal failure
  • Cough

Ramipril

26
Q

Consider the antihypertensives

What are the side effects of Beta-blockers?

Give an example

A
  • Hypotension
  • Confusion
  • Bradycardia
  • Lethargy
  • Impotence

SE profile better with more cardioselective drugs e.g. bisoprolol

Atenolol

27
Q

Consider the antihypertensives

What are the side effects of CCBs?

Give an example

A
  • Hypotension
  • Negatively inotropic
  • Fluid retention

Amiodarone

28
Q

Consider the antihypertensives

What are the side effects of loop/thiazide Diuretics?

Give an example

A
  • Hypotension
  • Hypokalaemia
  • Hyponatraemia
  • Confusion
  • Dehydration

Furosemide (Loop)
Bendroflumethazide (thiazide)

29
Q

Side effects of traditional antipsychotics which may be more pronounced in elderly

A
  • Confusion
  • Sedation
  • Parkinsonism
  • Tardive dyskinesia
  • Neuroleptic malignant syndrome
30
Q

In general, how do you approach the prescribing of older patients?

A
  • Consider the risk/benefit ratio
  • Pharmacokinetic factors
  • Start low and increase slowly
  • Review the effects of drug/dose changes
  • Communicate effectively with patients, carers and other professionals
  • Stick to the BNF
31
Q

How can you increase compliance of medication in the elderly ?

A
  • Consider cognitive problems, are there any carers/relatives to prompt patient to take medication?
  • Simplify regimens as much as possible. 1/2x /day
  • Use dossit boxes
  • Consider manual dexterity and vision
  • Check inhaler techniques
  • If dysphagic for large tablets, consider syrups/liquid formulations
32
Q

Which factors can increase the risk of adverse drug reactions?

A
  • age
  • length of stay in hospital
  • polypharmacy
33
Q

Which adverse effects may occur due to steroid use?

A
  • osteoporosis
  • gastric irritation
  • ulcers
  • hyperglycaemia
34
Q

Which adverse effects may occur due to TCA use?

A
  • cardiac arrhythmias
  • drowsiness
  • dry mouth
  • constipation
  • urinary retention
35
Q

Which adverse effects may occur due to NSAIDS use?

A
  • renal failure
  • gastric irritation
  • fluid retention
36
Q

Which adverse effects may occur due to a-blockers use?

A
  • drowsiness
  • hypotension
  • syncope

selective a-blockers can cause urinary retention (relax smooth muscle in BPH)

E.G. tamulosin, doxazosin

308: Clinical Pharamacology & Therapeutics (10 decks)

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