Pharmacology/prescribing Flashcards
Why do lipiphilic drugs such as anaesthetics/diazepam have a longer half life in older people?
Greater volume of distribution due to increased fat:muscle ratio
Why is GFR generally reduced in the elderly?
Decreased size, lower renal blood flow
What is the drawback of the MDRD equation for older people?
Older people have lower muscle mass, hence MDRD tends to over-estimate eGFR
What happens to the therapeutic index for drugs such as warfarin, lithium in older people?
Becomes narrow
How is the therapeutic index calculated?
LD50/ED50 (the median lethal dose over the median effective dose)
Erythromycin and clarithromycin are examples of…
Macrolide antibiotics
Interactions of macrolides? (2)
Theophylline
Statins
Key warfarin interactions (increase the INR) (7)
NSAIDs Cimetidine SSRIs Various antibiotics (metronidazole, macrolides, tetracyclines) Antiplatelets Cranberry juice Acute alcohol intoxication
What is the most potent enzyme inducer that reduces the INR of a person on warfarin?
Rifampicin
The hypoglycaemic effect of sulfonylureas is increased by which class of drug?
ACE inhibitors
Clopidogrel and PPI- effect?
Inhibits the effect of clopidogrel
Rare adverse effect of chloramphenicol?
Bone marrow suppression
What are the four drugs most commonly associated with adverse reactions in the elderly?
Warfarin
Digoxin
Insulin
Benzos
Problems with NSAIDs particularly in older people?
GI bleed risk, decline GFR, decreased effectiveness of anti-hypertensives and diuretics
Adverse effects of using antibiotics in older people without clinical evidence of infection?
C diff
Resistance
Why is hypovolaemia in response to diuretics more likely in older people?
Blunted thirst response
Examples of drug-disease interactions? (2)
Drugs with anticholinergic properties- precipitate urinary retention in men with prostatic hyertrophy
Benzodiazepines can precipitate delirium in a patient with dementia
What is the danger of oral hypoglycaemics in older patients? How can this be prevented?
Increased susceptibility to hypos, and decreased awareness of them. Avoid using longer-acting formulations, start low and go slow
Uncontrolled hypertension + renal bruit…?
Renal artery stenosis
Which commonly-prescribed class of drugs should be used with extreme caution in renal artery stenosis?
ACE inhibitors- precipitate renal failure
Monitoring for older patients being started on ACE inhibitors?
Baseline eGFR and electrolytes, before starting and before increasing doses
Co-morbidity which increases risk of ACE inhibitor-induced hypotension?
Aortic valve stenosis
Which electrolyte disturbance is a side effect of ACE inhibitor therapy, and concurrent prescription of which drugs enhances this risk?
Hyperkalaemia
Potassium sparing diuretics e.g. spironolactone
When can the tendency to hyperkalaemia of ACE inhibitors be useful?
When also on a potassium-losing diuretic, e.g. furosemide or bendroflumothiazide
Amiodarone interactions? (2)
Increases the effect of warfarin
Increased myopathy risk with statins
Adverse effects of amiodarone? (7)
Deranged TFTs in either direction Nausea and anorexia Photosensitivity Corneal microdeposits (reversible) Pulmonary fibrosis/alveolitis/pneumonitis Peripheral neuropathy Deranged LFTs
Indications for amiodarone?
Rate control, prevention of supraventricular tachyarrythimias (e.g. fast AF), prevention of paroxysmal ventricular tachyarrythmias
Adverse effects of NSAIDs in older people? (3)
Fluid retention
Renal toxicity- risk of acute tubular necrosis
Peptic ulceration –> GI bleeding
What are the consequences of fluid retention in older people? (3)
Worsening hypertension
Worsening heart failure
Ankle swelling
Which group of drugs should you avoid co-prescribing NSAIDs with?
ACE inhibitors- increases the likelihood of renal toxicity
Guidance for NSAID use in older people?
Use with extreme caution, avoid altogether in the very frail
Short periods, low dose, moderate potency
Avoid using two together (including aspirin)
What should you consider co-prescribing with NSAIDs in an older patient?
omeprazole
Potential issues with opioid analgesia in older people?
Constipation Nausea and vomiting Confusion Drowsiness Toxicity (respiratory depression)
Conditions for which oral steroids are commonly prescribed in older patients? (4)
COPD exacerbations
Colitis
Polymyalgia rheumatica
Rheumatoid arthritis
Bone protection for older patients on long-term (i.e. more than 2 weeks) steroids? (2)
Daily calcium and vitamin D
Bisphosphonate (daily/weekly)
Which basic clinical measurements should be monitored regularly when patients are on long-term steroids?
Blood glucose
Blood pressure
Why does increased blood pressure occur when treated with prednisolone?
Mineralocorticoid effect
Skin changes with steroid use? (4)
Purpura
Bruising
Skin thinning and fragility
Striae
Pattern of myopathy with steroid use?
Mostly proximal, causing problems such as rising from chairs
Why should steroids be given mane if possible?
Can cause acute confusion and sleep disturbance
Infections which are particularly common in long-term steroids?
Oral and genital candidiasis
Steroid rules for acute illness?
Double the usual oral dose; replace with IM hydrocortisone if NBM
Which condition can be “masked” by steroid use?
Peritonitis and/or perforation
Absolute indications for warfarin? (3)
PE
DVT
Heart valve replacement
Relative indication for warfarin?
Stroke prophylaxis in AF
