Pharmacology Flashcards
What is pharmacokinetics
How the body deals with a drug once administered
Involves absorption, distribution, metabolism and excretion
What is pharmacodynamics
How the drug acts on the body
How does pH of a drug affect its absorption
Acidic drugs need an acidic environment to be absorbed
Same is true for basic drugs
List examples of acidic drugs
Phenytoin
Aspirin
Penicillins
List examples of basic drugs
Diazepam
Morphine
Pethidine
Elderly patients absorb proportionally more basic drugs - why?
They secrete less stomach acid so less of an environment for acidic drugs to be absorbed
Why might elderly patients have less effective drug absorption
Less acid due to natural atrophy of parietal cells
Smaller surface area in the small intestine
Why must you consider drug delivery in elderly people
Need to take dysphagia into account for delivery - may need liquids
Consider NG/PEG tubes
Some may be NBM
Why do elderly patients have longer drug half lives?
The renal and hepatic clearance decreases which increases the half life – drug stays in system much longer
Elderly also have more fat so higher lipid sequestration
Higher fat to muscle content in elderly patients has what effect on drugs?
It increases the volume of distribution of lipophilic drugs and therefore increases their half life
What molecule binds acidic drugs in the body
Albumin
It is itself basic
What molecule binds basic drugs in the body
Alpha-1 Acid Glycoprotein
It Is itself acidic
How is hepatic metabolism affected by ageing
Reduced liver function due to decreased size,
blood flow, and disease
Reduction in first pass metabolism
Enzyme activity can also be reduced
How is renal metabolism affected by ageing
They will have decreased number of nephrons, size, tubular secretion and blood flow
Reduced GFR as a result
Why must you be careful using drugs with a narrow therapeutic index
Fine line between effective dose and lethal dose
Need to closely monitor
Give examples of drugs with a narrow therapeutic index
Theophylline Warfarin Digoxin Vancomycin Gentamicin
Which drugs most commonly cause adverse side effects in the elderly
Warfarin Digoxin Insulin Benzodiazepines Diuretics NSAIDs
What extra precautions should you take when starting opioids
Start lactulose or senna as prophylactically
Opioids cause significant constipation which can be dangerous in the elderly
What extra precautions should you take when starting steroids (long-term)
Long term use may need osteoporosis prevention
Need to monitor blood sugar regularly to watch for steroid induced diabetes
If taking levothyroxine, which other drug should be avoided
Calcium
It interferes with the absorption of levothyroxine
What are the major side effects of NSAIDs
GI haemorrhage
Decline in GFR
Decreased effectiveness of diuretics and anti-hypertensives
What are the major side effects of benzodiazepines and opioids
impaired psychomotor function
falls and confusion (should do fall assessment before prescribing)
What is the major risk with prescribing antibiotics in the elderly
Resistance
C diff infection - diarrhoea
How can we help reduce polypharmacy in the elderly population
Review medication regularly
Avoid treating drug side effects with more drugs
Try and find a drug that will treat more than one clinical problem
If stable, try a combination tablet
What is the STOPP-START tool
Used to indicate which medications are suitable and not suitable for the over 65s
When and why should you stop loperamide or codeine phosphate in the elderly
If treating diarrhoea of unknow cause because it can cause constipation, overflow diarrhoea, toxic megacolon and delay recovery from gastroenteritis
If treating severe gastroenteritis it can exacerbate the infection
When and why should you stop prochlorperazine or metoclopramide
If the patient has or develops Parkinson’s
as it can exacerbate it
When and why should you stop stimulant laxatives such as senna
If the patient has intestinal obstruction as it comes with a risk of bowel perforation
When should you start PPIs in the elderly
For severe reflux disease or structures
Give to those over 80 on anti-platelets and SSRIs
In those on aspirin and warfarin (rare)
When should you start fibre supplements
For those with chronic, symptomatic diverticular disease with constipation
when should you stop beta-blockers
If the patient is also on verapamil as there is a risk of symptomatic heart block
Non-cardioselective ones should be stopped in those with COPD as there is a risk
When should CCB be stopped
If the patient has chronic constipation In those with class III or IV heart failure
When should anti-hypertensives be started
treat where systolic blood pressure consistently >160mmHg
When do you start warfarin or DOACs
If they have chronic AF
Following a DVT or PE diagnosis
Which side effects must you consider in the elderly population
Risk of delirium
Bowel function - especially risk of constipation
Dizziness and balance issues - e.g. some drugs cause postural hypotension
List the common anti-cholinergic side effects
Confusion Hallucinations Tachycardia Blurred vision Urinary retention Constipation Dizziness Falls
Long term there is an increased risk of dementia
Which drugs can have anti-cholinergic side effect
Parkinson’s drugs Antidepressants Anti-emetics Opiates Antipsychotics Antihistamines
What is the risk of giving multiple anti-cholinergic drugs
Increases the risk of getting the adverse effects
