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SC WCS > Geriatrics SC050: Prescribing In Older People > Flashcards

Geriatrics SC050: Prescribing In Older People Flashcards

1
Q

Aging and Drug use

A

Prescribing in older people =/= in adults

Aging is associated with:
1. Chronic diseases
2. Acute illnesses
3. Disability
4. Frailty
—> Multiple drug use —> susceptible to adverse effects from drugs —> necessitating for dosage adjustment

Physiological changes with aging:
Pharmacokinetics —> ***Increase in plasma + tissue concentration:
1. Absorption (decrease)
2. Distribution
3. Hepatic elimination / metabolism (decrease)
4. Kidney elimination (decrease)

Pharmacodynamics —> ***Increase in drug effect:

  1. More sensitive to some drugs effects (esp. those act on CNS, CVS)
    - Hypotension with antihypertensive
    - Drowsiness with BDZ
    - Bradycardia with beta blockers
    - Bleeding tendency with anticoagulants
    - Postural hypotension / Electrolyte imbalance with diuretics
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2
Q

Elderly in Evidence based medicine

A
  • Elderly excluded from clinical trials, Treatment decisions are based on studies involving younger adults
    —> Benefit to risk ratio: different in frail older patients with co-morbidities
    —> Applicability of study findings to geriatric is limited
    —> Over-extrapolate of evidence can become biased
    —> May cause harm in elderly
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3
Q

Prescribing to reduce drug-related iatrogenic disease

A
  1. Think carefully before prescribing
  2. Prescribe with max knowledge about patient and therapeutics
  3. Monitor patient for efficacy and SE of medication
  4. Help patient make better use of their medication

Approach to optimise medication management:

  1. Avoid adverse drug reactions
  2. Reduce polypharmacy (Overuse)
  3. Avoid potentially inappropriate medications (Misuse)
  4. Enhance medication compliance
  5. Avoid clinically important drug interactions
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4
Q
  1. Adverse drug reactions
A

Harm **directly caused by drug at **normal doses during ***normal use

  • Harmful / Unpleasant reaction
  • From use of medicine
  • Predict hazard from future use
  • Warrant prevention / specific treatment / alter dose regimen / withdrawal of drug
  • Increase hospitalisation, prolong hospital stay, additional clinical investigations, trigger prescription cascade (new medications prescribed for conditions due to consequence of another medication)
  • **Drug history (esp. **OTC very important)

Important risk factors:

  1. Old age
  2. Impaired RFT
  • Types of reaction (ABCDE):
    1. Dose-related (    *Augmented)
  • common
  • related to pharmacological action of drug
  • predictable
  • low mortality
  • e.g. phenytoin toxicity, anticholinergic effects of TCA
  1. Non-dose-related (**Immunological reactions, **Bizarre)
    - uncommon
    - unrelated to pharmacological action of drug
    - unpredictable
    - high mortality
    - e.g. penicillin allergy
  2. Dose + Time-related (**Cumulative dose, **Chronic use)
    - uncommon
    - e.g. chronic steroid use causing HPA axis suppression
  3. Time-related (***Delayed)
    - uncommon
    - usually dose-related
    - occurs / becomes apparent some time after use of drug
    - e.g. parkinsonism from neuroleptic drugs
  4. Withdrawal (***End of use)
    - uncommon
    - occurs soon after withdrawal of drug
    - e.g. opioid / BDZ withdrawal syndrome
  5. Unexpected failure of therapy (**Failure)
    - common
    - dose-related
    - often caused by **    drug interactions
    - e.g. reduce anticoagulation effect of warfarin by phenytoin (enzyme inducer)

Common drugs causing hospitalisation:

  1. Warfarin —> GI bleeding
  2. Antiplatelets —> GI bleeding
  3. Insulins —> Hypoglycaemia
  4. Hypoglycaemic agents —> Hypoglycaemia
  5. NSAID —> GI bleeding
  6. Diuretic —> Dehydration / HypoNa / HypoK
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5
Q

Indapamide (Natrilix)

A
  • Thiazide-like diuretic drug
  • for HT

Common SE:

  1. HypoNa (risk factors: Age, Low BW, HypoK)
  2. HypoCl
  3. HypoK
  4. Dehydration
  5. Tiredness / Weakness
  6. Orthostatic hypotension
  7. Dizziness
  8. Hyperuricaemia
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6
Q

Zopiclone

A
  • Non-BDZ hypnotic
  • Overcome some disadvantage of BDZ —> next day sedation, dependence, withdrawal
  • Licensed for short-term treatment of insomnia in situations where insomnia is debilitating / causing severe distress
  • Long-term continuous use not recommended
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7
Q
  1. Drug-disease interaction
A
  • **Exacerbations of **pre-existing diseases / conditions / syndromes by medication
  • More common in older adults —> Multiple chronic diseases + Multiple medications
  • More adverse clinical impact (less reserve than younger individuals)

Clinically important drug-disease interactions:

  1. Anticholinergics (decrease Detrusor tone + impair bladder sensation) / Sympathomimetics (increase smooth muscle tone in bladder neck) in URTI in BPH patients —> AROU
  2. NSAID in CRF
  3. Anticholinergics, opioid, TCA in constipation
  4. Steroids in DM (monitor glucose + may want to consider insulin / hypoglycaemic)
  5. Antipsychotics, sedative-hypnotics, TCA, BDZ, Antihypertensive in falls
  6. Digoxin, TCA, Beta blockers in heart block
  7. Anticholinergics in narrow-angle glaucoma (∵ cause pupil dilation)
  8. Metoclopramide, Antipsychotic in PD
  9. Aspirin, NSAID in peptic ulcer disease
  10. Alpha blockers, Antihypertensive in syncope
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8
Q
  1. Drug-drug interaction
A
  • Clinically significant alteration in effect of one drug (object drug) as a result of co-administration of another drug (precipitant drug)
  • May have potentially ***life-threatening consequences in older adults, who may take several drugs at once
  • Elderly more susceptible
    —> Age-related PK + PD change
    —> Increased risk for diseases
    —> Increase in medication use
  • DDI are **predictable —> **avoidable + ***manageable

DDI can be PK / PD in nature:
PK:
1. One drug can change absorption / distribution / metabolism / excretion of another drug
- Interactions —> changes in serum drug concentration —> change clinical response
- Most frequency PK DDI are **CYP450, drug transporter e.g. **P-glycoprotein

CYP450 Enzyme inducer:

  1. Phenobarbitone
  2. ***Phenytoin
  3. Primidone
  4. ***Carbamazepine
  5. ***Rifampicin

CYP450 Enzyme inhibitor:

  1. Amiodarone
  2. Diltiazem
  3. Verapamil
  4. Ciprofloxacin
  5. Clarithromycin
  6. Azole (Itra / Keto / Flu)
  7. Metronidazole
  8. Sulphonamides
  9. Cimetidine

Substrate (decreased / increased by inducer / inhibitor):

  1. Antidepressant
  2. CCB
  3. Corticosteroid
  4. Cyclosporin
  5. Theophylline
  6. Thyroxine
  7. ***Warfarin

PD:
- Amplification / Decrease in therapeutic effects / SE of a specific drug by interacting drug
- Elderly has reduced homeostatic mechanism
—> particularly sensitive to combined effects of 2 drugs
—> even if only additive and not synergistic —> can be sufficient to cause adverse effects

Postural hypotension from combination of:

  1. Nitrate (for IHD)
  2. CCB (for IHD / HT)
  3. ACEI (for HT)
  4. Alpha blocker (for BPH)
  5. Antiparkinsonism drug (for PD)

Sedative effects + Falls from combination of:

  1. Antihistamine
  2. Hypnotic
  3. Antipsychotic
  4. Anticonvulsant

Management of DDI:

  1. Review all drugs for appropriate indications
  2. Discontinue the drug causing interaction / drug affected by interaction
  3. Substitute suspected drug with another drug of similar efficacy but lower potential for interaction
  4. Decrease dose
  5. Change time of administration
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9
Q

Warfarin drug interaction

A
  • Mainly metabolised by CYP450

- CYP450 (2C9, 1A2, 3A4) enzymes systems inducer / inhibitor —> alter warfarin metabolism —> change INR

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10
Q
  1. Polypharmacy
A
  • Use of multiple medications by a patient
  • Variable definition: 5-10 medications generally
  • Prescribed + OTC + Herbal / Supplements

Problems:

  1. Adverse drug reaction
  2. Drug-disease interaction
  3. Drug-drug interaction
  4. Poor compliance
  5. Inappropriate drug use
  6. Medication errors

Adverse clinical outcomes:

  1. Disability + Cognitive impairment
  2. Falls, fractures
  3. Malnutrition
  4. Hospitalisation
  5. Institutionalisation
  6. Mortality
  7. Rising healthcare costs

Management:

  1. Deprescibing
    - supervised **withdrawal of inappropriate / no longer needed medications (in which potential harm > benefit) / **taper medications to minimum effective dosage
    - part of good clinical practice
    - through medication review
    - benefits: polypharmacy reduction, reduced fall risk, improved cognition + psychomotor function
    - feasible and safe
    - benefits and risks of medications can be balanced according to patient’s **current health status (e.g. prevention of stroke in end-of-life patients)
    - particularly relevant to patients with burden of polypharmacy / **    changing clinical conditions

Process of deprescribing:

  1. Obtain complete drug list
  2. Ask drug compliance / drug not taking + reasons
  3. Review indications, S/S, efficacy, SE —> Potential drug to be off / tapered
  4. Talk to patient cessation regimen e.g. order + time frame of discontinuation (begin with drug with lowest benefit-to-harm ratio, lowest risk of withdrawal S/S)
  5. Support + monitor for adverse effects / withdrawal S/S
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11
Q

Prescribing cascade

A
  • Common cause of polypharmacy
  • Adverse drug effect misinterpreted as a new medical condition —> prescription of another drug —> additional unnecessary medications that add to patient’s medication burden + increased risk of polypharmacy

Example:

  1. BPSD —> Antipsychotic —> EPS —> Levodopa (but will not work since drug-induced EPS not respond to levodopa)
  2. NSAID for OA —> Hypertension (from chronic NSAID use) —> Hydrochlorothiazide —> Increase uric acid / gout —> Colchicine + Allopurinol
  3. CCB —> Ankle edema —> Diuretic —> HypoNa / HypoK —> Na / K supplement

Management:

  1. Make sure is clinically indicated before prescription
  2. Avoid prescribing cascade (ask yourself if the drug is used to treat SE of another drug) —> Prescription of drugs for treating drug SE should be ***avoided in elderly
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12
Q
  1. Medication non-compliance
A

Cause:

  1. Medication
    - Polypharmacy
    - Complex regimen
    - SE profile
    - Convenience factors (e.g. dosing frequency)
  2. Disease / Condition
    - Asymptomatic (e.g. DM, HT)
    - Mild severity
  3. Patient
    - Understanding / disagreeing with treatment plan
    - Memory problems
    - Behavioural problems
    - Poor organisation
    - Difficulty taking (vision, dexterity, pill dysphagia)
    - Affordability
    - Lack of carer supervision

Solutions:

  1. Medication
    - Simplify regimen
    - Reduce frequency
    - Combination drug regimen
  2. Disease / Condition
    - Educate patients + caregivers
  3. Patient
    - Engage family member
    - Education / Drug counselling
    - Clear / Written instructions
    - Pillbox
    - Community nurse
    - OAH
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13
Q

***Principles of prescribing in elderly

A

Before prescription:

  1. Medical history + Cognitive history
  2. Medication history
    - Hospital records
    - Private doctors
    - OTC
    - TCM / Herbal / Supplement
  3. Social history

Prescribe only if it is necessary:

  1. Always look for ***Non-drug alternatives
  2. Avoid over / underuse
  3. Lowest possible effective dose (Start low + Go slow)

Process:

  1. Right drug
  2. Right dose
  3. Right route
  4. Start low + Go slow
  5. Aware of SE
  6. Check RFT
  7. Check allergy

After prescribing:

  1. Monitor for efficacy, SE
  2. Check compliance
  3. Discontinue unnecessary medications

Lastly:

  1. Do not harm
  2. Consult if queries
    - Colleague / Pharmacist
    - Pharmacology / Medicine books
    - BNF, MIMS
    - Electronic devices, internet
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14
Q

Summary

A
  • Elderly subjects take more medications than any other age group
  • Age-related changes in pharmacokinetics + pharmacodynamics lead to a reduction in physiologic reserves —> Increasing risk of:
    —> Adverse drug reactions
    —> Drug-drug interactions
    —> Drug-disease interactions
    —> Polypharmacy
  • Special attention is needed in prescribing among elderly population in order to prevent adverse outcomes
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