Drugs in older patients

Question 1

Changes in absorption in older population

Answer 1

Iron and calcium absorbed more slowly

Otherwise largely unchanged despite delayed gastric emptying and reduced motility

Question 2

Changes in distribution in older population

Answer 2

Reduced lean body mass –> need reduced dose for drugs with narrow TI (e.g. digoxin)

Decreased muscle mass –> higher initial concentration of water-soluble drugs (e.g. digoxin)

Increased fat proportion –> prolonged elimination of fat-soluble drugs (e.g. benzos)

Reduced plasma protein –> increased free fraction (And effective dose) of drugs e.g. warfarin, furosemide

Question 3

Changes in hepatic metabolism in older patients

Answer 3

Mainly affects drugs with extensive first-pass metabolism (e.g. nitrates, propranolol)

Illness, reduced mass/function, reduced blood flow all reduce metabollism

Question 4

Changes in renal excretion in older patients

Answer 4

Ageing kidney - very common

Compounded by dehydration and urinary sepsis

Reduced elimination of many drugs

Question 5

Drugs/metabolites excreted by kidneys

Answer 5

Lithium

Furosemide

Digoxin

Gentamicin

Tetracycline

Question 6

Drugs that may require dose adjustment in older patients

Answer 6

ADD A WOON!

• ACE inhibitors (renal)
• Diazepam
• Digoxin
• Aminoglycosides
• Warfarin
• Opiates
• Oral hypoglycaemics
• NSAIDs

Question 7

Effects of digoxin toxicity

Answer 7

• CNS: Xanthopsia, blurred vision, photophobia, confusion
• Cardiac: Arrhythmias, bigeminy/trigeminy, complete heart block
• GI: Anorexia, N+V, occasionally diarrhoea

Question 8

Common drug interactions of digoxin

Answer 8

• Antimalarials
• Antiarrhytmics (amiodarone)
• Ca channel blockers
• Diuretics/laxatives –> K+ depletion
• Macrolides –> disruption of gut flora

Question 9

Management of digoxin toxicity

Answer 9

• IV potassium - 40mmol in 5% dextrose
• IV Magnesium - 50ml of 2% Mg sulfate
• DSFabs - 60x ingested dose

Question 10

Liver enzyme inhibitors - increase effect of warfarin

Answer 10

Omeprazole

Disulfiram

Erythromycin

Valproate

Isoniazid

Cimetidine

Ethanol (acute)

Sulfonamides

Question 11

Liver enzyme inducers - decrease effects of warfarin

Answer 11

Phenytoin

Carbamazepine

Alcohol

Rifampicin

Barbiturates

Sulphonylureas

Question 12

Target INR on warfarin

Answer 12

2. 5 normally
3. 5 for mechanical heart valves

Question 13

Management of raised INR on warfarin

Answer 13

1. Correct cause
2. Stop warfarin - monitor reduction
3. Give vitamin K if INR >8 (not routinely, disrupts anticoag for weeks)
4. Give VitK and FFP if bleeding
5. Prothrombin complex concentrate if urgent

Question 14

Drugs causing SIADH

Answer 14

Cyclophosphamide

Carbamazepine

Thiazide diuretics, tricyclic antidepressants

Vincristine, vinblastine

Question 15

Drugs causing confusion

Answer 15

6As is OCD

Antidepressants (esp TCAs)

Antipsychotics, lithium

Anticholinergics

Anticonvulsants

Anxiolytics

Antihistamines

Opiates

Corticosteroids

Diuretics (electrolytes), digoxin

Question 16

Drugs contributing to incontinence in older patients

Answer 16

Diazepam

Amitriptylline

Diuretics

Codeine

Question 17

Problems with ACE inhibitors in older patients

Answer 17

Renal failure

Hypotension

Cough

Hyperkalaemia (esp with K-sparing diuretic)

Question 18

Problems with NSAIDs in older patients

Answer 18

Fluid retention - hypertension + cardiac failure

Renal - e.g. acute tubular necrosis (caution with ACEis)

Gastic bleed (gastroprotection coprescribed)

Question 19

Adverse effects of opioids in older people

Answer 19

Constipation

N+V

Anorexia

Confusion

Drowsiness

Respiratory depression

Question 20

Side effects of long-term steroids

Answer 20

Cataracts

Ulcers

Skin thinning, purpura, bruising

Hypertension, hrisutism, hyperglycaemia

Infections

Necrosis of femoral head

Gait: proximal muscle weakness

Osteoporosis