DRUGS Flashcards
ACEi ARBs Beta-blockers Diuretics
What is the mechanism of action, indications, and contraindications of GTN?
MOA: Venodilation.
Reduces venous return to the heart, reducing preload and myocardial oxygen requirement
INDICATIONS: stable angina, heart failure associated with acute MI (infusion)
CONTRAINDICATIONS: hypotension, hypovolemia, raised ICP
List 3 common adverse effects of GTN
Headache Flushing Palpitations Orthostatic hypotension Fainting Peripheral oedema
What is the mechanism of action, indication, and contraindication of ACE inhibitors?
MOA: Prevents the conversion of angiotensin I to II, inhibiting the vasoconstrictive, sodium retention, and aldosterone-releasing effects of ang II. Also inhibits bradykinin breakdown (bradykinin is a vasodilator).
INDICATIONS:
- Hypertension
- HFrEF
- Diabetic nephropathy
- Prevention of progressive renal failure in patients w/>1g per day of proteinuria
- Post-MI
CONTRAINDICATIONS:
- Hx of intolerance
- Hx of hereditary or idiopathic angioedema (rare, but serious)
- Pregnancy
- Renal Artery Stenosis to all functioning kidneys
What are the RELATIVE contraindications of ACE inhibitors?
- Hypotension (<90mmHg)
- Hyperkalemia (K>6): can cause arrhythmias, death
- Renal impairment
What causes the ACE inhibitor-induced cough?
ACE inhibitors prevent the breakdown of bradykinin.
Bradykinin accumulation can cause cough (in 5-10%) due to pro-inflammatory peptides and local release of histamine.
How does GTN dosage differ for angina and acute decompensated HF?
GTN dosage for ADHF is much higher. At this dosage, it dilates the arteries as well as the veins.
This decreases the afterload so the heart doesn’t have to pump against as much resistance.
FOR PATIENTS ON ACE INHIBITORS:
When GFR relies heavily on the _______ arteriole, renal impairment is more common.
When GFR relies heavily on the EFFERENT arteriole, renal dysfunction is more common.
Give 2 examples of diseases in which GFR relies heavily on the efferent arteriole.
- Elderly
- Dehydrated
- Renovascular disease
- Pre-existing renal dysfunction (less nephrons, so each carries a greater load)
How are ACE inhibitors and ARBs cleared?
Renally
When are angiotensin receptor antagonists used?
When ACEi are contraindicated (e.g. angioedema) OR there is an ACEi-induced cough
Why don’t Angiotensin receptor antagonists cause coughing?
Don’t act on bradykinin
Why are Angiotensin II receptor antagonists/blockers NOT first-line?
In some indications, they are less effective than ACEi and less proven
Angiotensin receptor antagonists end in …?
-sartan
Describe the mechanism of action, indications, and absolute contraindications of beta-blockers.
MOA: blocks beta-receptors (heart, lung, eye, kidney, liver, brain, pancreas, bronchi, etc.), thus preventing them from being activated by adrenaline and noradrenaline.
Can be selective and non-selective. They are competitive ANTAGONISTS.
Reduces HR, BP, and contractility.
INDICATIONS:
- HTN
- Heart failure/HFrEF
- Angina
- Tachyarrhythmias
- MI
ABSOLUTE CONTRAINDICATIONS:
- Hypotension
- Bradycardia
- Uncontrolled HF
- 2nd or 3rd degree AV Block
- Severe or poorly-controlled REVERSIBLE airway disease (e.g. asthma)
Basically, whenever the cardiovascular effects are undesirable
How does the MOA differ between SELECTIVE and NON-SELECTIVE beta-blockers?
SELECTIVE beta-blockers only block beta-1 receptors
NON-SELECTIVE blocks both beta-1 and beta-2
List 3 common adverse effects of beta-blockers
- Bradycardia
- Hypotension
- Orthostatic Hypotension
- Transient worsening of HF (when first commenced)
- Nausea
etc.
Why do beta-blockers need to be used with caution in diabetics?
Can mask symptoms of hypoglycaemia
the hypogylcaemia is the issue, NOT the beta-blocker
Why are diuretics less useful in LEFT-sided heart failure?
There doesn’t tend to be fluid overload, so there is less need for them. More useful in RHF when you have things like peripheral oedema and fluid overload.
What is the MOA of beta-lactam antibiotics? (Drug class: penicillins)
MOA: interfere with bacterial cell wall growth
Why are anti-staph agents used in place of standard penicillins (e.g. penicillin G, V)?
Most staphylococcal infections are resistant to standard penicillins
Name an example of an anti-staph penicillin
Flucloxacillin
(note: when talking about methicillin-resistant staphylococcus aureus/MRSA, it refers to a bug that responds to flucloxacillin)
When are empiric antibiotics recommended in IE?
For haemodynamically unstable patients.
Targeted antibiotics are recommended for everyone.
What is the difference between immunologically and non-immunologically mediated reactions caused by penicillin?
NON-IMMUNOLOGICAL REACTIONS/INTOLERANCES: diarrhoea, headache, vomiting
IMMUNOLOGICALLY-MEDIATED: allergies (e.g. SJS, TENS, immediate hypersensitivity)
Does re-exposure to penicillin in someone who is allergic cause a better or worse reaction?
WORSE
How are aminoglycosides administered? Why?
Injection or topical
They are not bioavailable orally
How are aminoglycosides cleared?
100% renally
What type of infections are aminoglycosides used for? Give an example of an aminoglycoside.
Serious gram-negative infections
E.g. gentamycin (most commonly-used)
List 3 adverse effects of aminoglycosides
Hearing loss
Ataxia
Renal dysfunction
What types of infections is vancomycin (glycopeptide) used for?
Gram-positives resistant to penicillin
and anaerobes
IS EFFECTIVE AGAINST MRSA
What similarities are shared by aminoglycosides and vancomycin?
Both renally-cleared
Both not absorbed orally (IV administration)
What is vancomycin useful for? Why is its use restricted?
MRSA
To reduce pressure for vancomycin-resistant staph aureus
What is the drug class of vancomycin?
Glycopeptide
How do beta-blockers help with left-sided ventricular failure?
Block SNS action on beta-1 receptors in the AV Node –> slows HR –> increases time in diastole –> increases ventricular filling time –> increased preload –> greater stretching of actin and myosin filaments (Starling forces) –> greater contractility –> improved LVEF
Compare furosemide and spironolactone for CHF, taking into account:
- MOA
- Contraindications
- Adverse effects (especially on electrolytes)
FUROSEMIDE (loop diuretic)
1. MOA: inhibits Na+ and Cl- reabsorption in the ascending LOH, which is responsible for ~20% of Na+ reabsorption
- Contraindications/Precautions: allergy, gout, severe sodium and volume depletion
- Adverse effects (especially on electrolytes): hyponatraemia, hypokalaemia, hypomagnesaemia, hypochloraemia, hypocalcaemia, gout, orthostatic hypotension, dehydration
SPIRONOLACTONE (aldosterone antagonist):
1. MOA: inhibits Na+ absorption in the distal tubule by antagonising aldosterone, increasing Na+ and water excretion and decreasing K+ excretion.
- Contraindications/precautions: renal failure, debilitated patients with cardiopulmonary disease or uncontrolled diabetes, prostate cancer, cirrhosis
- Adverse effects (especially on electrolytes): hYPERKALEMIA, hyponatremia, weakness, headache
LOOP diuretics are very powerful. Aldosterone antagonists less so.
What do NSAIDs do to the afferent arteriole?
NSAIDs that cause COX-1 and COX-2 inhibition can reduce renal blood flow by constricting the afferent arteriole.
What organisms is gentamicin used for?
Gram-negative
What organisms is metronidazole used for?
Anaerobes
Which aspects should be included in a penicillin ‘allergy’ history?
- What they reacted to
- What type of reaction it was: GIT, cardiovascular, rash/urticaria, swelling, seizure, dizziness, headache, etc.
- How long after the treatment did it start?
- How long ago did they have this reaction?
- How was the reaction treated?
- What other antibiotics have they had since? (e.g. cephalosporins)
What would a penicillin INTOLERANCE look like?
Not actually an allergy
GIT: nausea, vomiting, diarrhoea
Neurological: dizziness, headache, confusion
Other, e.g. thrush in women
Give 3 examples of low-risk reactions to penicillin
- Unknown reaction >10 years ago
- Childhood exanthem (details unclear and no severe features or hospitalisation)
- Diffuse or localised rash with no other symptoms AND occurring >24hrs later AND >10 years ago
Give 3 examples of HIGH-risk reactions to penicillin
- IgE-mediated hypersensitivity: urticaria, angioedema, swelling of the mouth and throat, distress, collapse, death
- Any history of diffuse rash a short time after starting the medication (e.g. within 2 hours)
- Diffuse or localised rash that was DELAYED, BUT within the last 10 years
What reaction would you get upon re-exposure to penicillins after a previous high-risk reaction?
Possibly the same rash but worse, and with anaphylaxis
Outline the approach to antibiotic prescription in someone who was previously had a high-risk reaction to penicillin.
Choose a non-beta lactam antibiotic
Don’t use cephalosporins due to cross-reactivity risk
State the following information for PENICILLINS:
- Mechanism of action
- Why does resistance develop?
- Bioavailability
- Clearance
- Spectrum of action
MECHANISM OF ACTION: interferes with bacterial cell wall growth
RESISTANCE: due to beta-lactamase, modification of penicillin binding protein, no access to PBP, efflux pump
BIOAVAILABILITY: good oral bioavailability, but varies between benzyl penicillin (15%) and amoxicillin (80%)
CLEARANCE: Renal (generally)
SPECTRUM OF ACTION: very narrow to very wide
Which patient groups tend to develop renal impairment when using ACEi?
Anyone can, but the risk is HIGHEST in those whose GFR depends on the EFFERENT arteriole.
- Elderly
- Kidney disease (less nephrons, so heavier filtration load on each nephron)
- Those with renovascular disease
- Dehydrated
What should be monitored in patients taking ACEi?
Within 1-2 weeks of commencement, or before dose changes, the following should be evaluated:
- Potassium
- Renal function
- BP
- Side effects: cough, angioedema (may not be recognised by the patient as related to their meds)
When are ARBs used?
When there are contraindications (e.g. angioedema)
When ACEi aren’t tolerated (e.g. cough is very annoying)
They don’t act on bradykinin and hence won’t cause these side effects
Why are ACEi preferred over ARBs?
ARBs are less effective than ACEi for some indications
What should be monitored in patients taking ARBs?
Within 1-2 weeks of commencement, or before dose changes, the following should be evaluated:
- Potassium
- Renal function
- BP
i.e. same as ACEi but minus the side effects
Can ACEi and ARBs be stopped without taper?
YES
Why is amiodarone so widely-sued?
Can be used to supraventricular and ventricular arrhythmias
Outline the de-prescribing pathway for beta-blockers and why it must be done gradually
May need to reduce dose 2 weeks at a time over a period of 6-8 weeks (especially if they’ve been on it for years)
Weaning off slowly prevents the recurrence of angina & tachyarrhythmias
What is the mechanism of action of calcium channel blockers?
Blocks the effect of calcium channels on cell membranes. This results in:
- Vascular smooth muscle: Arteriolar relaxation
- Myocardium: reduces force of contractility
- Cardiac conduction: reduces HR
i.e. it opposes the normal physiological effects of calcium influx
Why do calcium channel blockers come in a sustained release tablet?
Most have a short half-life
What do calcium channel blockers end in?
Depends on the class:
Dihydropyridines end in ‘-ine’ (e.g. felodipine, amlodipine)
Non-dihydropyridines are verapamil and diltiazem
How many different classes of calcium channel blockers exist?
3 classes:
Dihydropyridines (selective for peripheral vascular tissue)
Diltiazem
Non-dihydropyridines (selective for myocardium)
What are the indications for calcium channel blockers?
Hypertension
Angina
What are the side effects of calcium channel blockers and how does this relate to their MOA?
Dihydropyridines are selective for peripheral vascular tissue. They have a more profound vasodilatory effect and can cause side effects such as ankle swelling.
Non-dihydropyridines can cause constipation (especially verapamil) and bradycardia.
Common adverse effects: nausea, flushing, dizziness, headache, hypotension.
Can calcium channel blockers be stopped suddenly?
YES