Flashcards in Adverse reactions Deck (43):
Drug classes ordered in prevalence of adverse reactions?
NSAIDs (29.6%); Diuretics (27.3%) ; Warfarin (10%)
Side effects to NSAIDs
Bleeding, renal impairment and wheezing
Side effects Diuretics
Hypotension (biggest cause of falls); electrolyte disturbances (monitor plasma potassium!)
What is a useful response to dealing with a type A adverse reaction?
Reduce the dosage, since these are predictable
Side effects TCAs? (type a)
Side effects Beta blockers (type a)
Beta blockers (type a)
bradycardia (below 60)
Opioids (type a)
constipation or hallucinations
Antibiotics (type a)
Ivabradine (type a) used for IHD and HF (blocks pacemaker current)
Monitor HR, risk of bradycardia
Cimetidine or Spironolactone (type a)
NSAIDs (type a)
Asthma caution and GI damage
The biggest burden of ADR. insidious because OTC and abundant. 2000 deaths per year
Prescribe with caution, consider alternative
Who is at risk of GI damage? Co-prescribe a PPI if suspicious
Digoxin (type a)
Nausea, vomiting and visual disturbances
Cytotoxics (type a)
beta blockers (type a)
asthma: beta 1 selective, can block beta adrenoreceptors. risk of bronchospasm.
HF + COPD: add beta-1 block brosoprolol for HF, but monitor lung function if they have COPD
Describe pharmacokinetic mechanism
Absorption; elimination (renal and hepatic clearance)
To avoid an ADR, what key consideration should you make when prescribing digoxin?
How does diazapam's half-life change with age?
one hour increase per year beyond 20 y/o
When should you be cautious in who to prescribe diazepam to?
Neonates; elderly; enzyme defect populations (10% genetic defect to p450 enzyme); hepatic (LFT poorly predicts metabolism)
What are type B ADRs?
unpredictable, severe, un-related to pharmacology, rare, genetic or immunological
Respond not by reducing dose, but stopping the medication
What is agranulocytosis ? common examples?
Type B ADR; reduction in WBCs (absence of neutrophils, increased susceptibility to mouth ulcers, infections).
Clozapine is a common example. These patients require freq monitoring
Bruising, easy bleeding- Type B ADR.
Are NSAIDs a risk to people with CV disease?
yes, it can worsen it. This is due to fluid retention, exacerbation of hypertension.
diclofenac is a no no!!!! (when used topically as a skin preparation it is ok)
Does NSAIDS increase risk of renal failure?
Yes, reduction of eGFR
Myopathy (actual muscle damage--> rarely, rhabdomylosis--> kidney failure)
'Routinely say that ''it can cause muscle pain, if so, require blood test to see if there's muscle damage''
irritation--> life threatning*
Erythematous erruptions: reddening, may resemble measles or maculopapular
Toxic epidermal necrolysis: rare but often fatal with blistering and skin peels off
Stevens-Johnson syndrome: fever, rash, blisters
Green blood. Once in a career occurrence
Monitor what with ACE-I?
Risk of drug interactions exacerbated by what?
Renal impairment (ageing patient)
Drugs with narrow therapeutic window pose greatest problem (lithium, warfarin, digoxin)
OTC does not necessarily = safe
Elicit drugs important to rule out
tetracycline: binds Fe, calcium in milk. Not absorbed.
Avoid taking with dairy products
PPIs, antacids, H2 antagonists raise pH, can affect absorption of certain drugs
CYP related metabolism
Induction or Inhibition
Examples of drug induction.. how does this occur?
St. John's Wart (weakly effective anti-depressant)
Conc of barbiturates, carbamazepine, rifampicin increase metabolism of OCs
May take a week or 2 for effect
Effect may persist on stopping inducer
Example of drug inhibition. How does this occur?
erythromycin / clarithromycin (avoid with simvostatin--> increases in conc, muscle damage)
Psoralen (from grape fruit juice)
i.e. macrolide + warfarin- patient bleeds, or even h.stroke.
Rapid onset : 1-2 days
Often reverse quickly on stopping
Drugs to avoid with simvostatin
For amlodipine plus statin:
Pravastatin does not interact
Use 20mg simvastatin as maximum dose
Key counselling point for methotrexate?
Do not self-prescribe with aspirin or NSAIDs: competition for renal elimination, toxicity risk. Also risk of impaired renal perfusion
rhuematologists might be happy to co-prescribe becaue they monitor blood count.
Drug interactions can be acceptable if carefully monitored
Heart failure patient on diuretic are you safe to use ACE-I??
Risk of first dose hypotension: stop diuretic for a few days
Another risk of diuretics?
Risk of hypokalaemia: digoxin risk. Take K levels beforehand
Asthma and beta-blockers?
Salbutamol's effectivity (B2 agonist) reduced due to beta blocker activity
Calcium channel blockers?
Verapamil etc can act on calcium heart channels. Thus using this drug and beta blocker could stop the heart!!
Dihydropyridine does not act on Ca channels of heart, limited to smooth muscle Ca channels.
Dangers of using Warfarin. Named alternatives
So many interactions: inducers and inhibitor susceptibility
INR: monitor (1 in healthy patient, value increases when blood coagulating less). i.e. measure 3 days after prescribing with macrolide, if it increases, reduce warfarin dose.
Increased actions lead to bleeding:
blood in faeces
blood in urine
Reasons why it's being used less.
Direct Oral Anticoagulants
Factor X inhibitor
No requirement to monitor
Examples of alcohol interactions
Labels 2 & 4 (avoid if affected or avoid)
Mostly CNS depressant / sedating actions enhanced
E.g. TCAs, sedating antihistamines, benzodiazepines
Few antibiotics actually interact
Metronidazole leads to disulfiram-like effect
Avoid aspirin containing products for hangover
Cranberry juice thought to potentiate warfarin leading to fatalities
Grapefuit juice interacts with simvastatin and some Ca-antagonists