Cardiovascular drugs Flashcards
Describe the basis of hypertension treatment
Hypertension treatment options will be based on blood pressure reading(s), patients’ CVD risk and other co-morbidities.
Describe ACEIs
The RAAS system
- Regulates BP by ↑ or ↓ blood volume through modulating renal function
- Renin secretion influenced by
- Reduced renal perfusion
- Reduced Na+ concentration in distal tubular fluid
- Angiotensin II
- Potent vasoconstrictor
- Causes release of aldosterone
- Na+ and water retention
- ACE Inhibitors and Angiotensin II receptor blockers and aldosterone antagonists block this system at various points
ACEI
- Stop the renin-angiotensin pathway by inhibiting the conversion of angiotensin I (no appreciable activity) to angiotensin II (potent vasoconstrictor)
- Inhibit vascular tone
- directly lower BP
- Inhibit aldosterone release
- indirectly lower BP
Describe AngII receptor antagonists or sartans
RAAS:
- Regulates BP by ↑ or ↓ blood volume through modulating renal function
- Renin secretion influenced by
- Reduced renal perfusion
- Reduced Na+ concentration in distal tubular fluid
- Angiotensin II
- Potent vasoconstrictor
- Causes release of aldosterone
- Na+ and water retention
- ACE Inhibitors and Angiotensin II receptor blockers and aldosterone antagonists block this system at various points
AngII receptor antagonists (sartans)
- Drugs that bind at the AT1 receptor to block action
- decreased vasoconstriction, increased salt excretion
- More direct as drug target so limited effect on serum K+ (v inc. in ACE use)
- No effect on bradykinin metabolism (cough physiology in ACEi use)
- Reduced adverse effect profile
Advantages and disadvantages of ACEI/ARB
- Recommended as first-line treatment of hypertension, especially those with DM, heart failure, CVD/IHD, or proteinuric chronic kidney disease
- No rebound hypertension
- Long-term benefits on cardiac remodelling and kidney disease with proteinuria
Define and describe the consequences of the triple whammy
The ‘triple whammy’
of ACEI, NSAID, diuretics…leading to reduced renal perfusion and acute kidney injury (AKI).
Describe calcium channel blockers
Increased concentrations of cytosolic calcium cause increased contraction in both cardiac and smooth muscle cells (↑ calcium = ↑contractions = ↑ BP)
Calcium channel blockers (CCB’s) all produce effects by binding to the alpha1 subunit of L-type-Calcium channels
- Blocking inward movement of calcium through the slow channels of the cell membrane of cardiac and smooth muscle cells
- Activity varies depending on the type of cardiovascular cells involved:
- Myocardium
- Cardiac Conduction System (SA and AV nodes)
- Vascular Smooth Muscle
- ↓ BP by ↓PVR
- Myocardium
- Two main classes of CCB’s
- Non-dihydropyridines (target vascular and myocardial cells)
- diltiazem
- effects:
- Targets peripheral blood vesselsand cardiac calcium channels
*Less effect on the heart compared to verapamil
*↓ HR and mean arterial BP - DRUG INTERACTIONS (CYP inhibitor)
- Targets peripheral blood vesselsand cardiac calcium channels
- side effects:
- bradycardia
- constipation
- AV block
- worsening heart failure
- effects:
- verapamil (used as anti-arrhythmic)
- effects:
- targets primarily cardiac calcium channels
- strong cardiac depressant effect: decreased heart rate and CO
- reduces AV conduction and blocks SA node
- decreased PVR and BP
- drug interactions: CYP inhibitor
- side effects:
- bradycardia
- constipation
- AV block
- worsening heart failure
- effects:
- diltiazem
- Dihydropyridines (target peripheral vascular smooth muscle)
- amlodipine, nifedipine, felodipine
- effects:
*More selective as vasodilators and have less cardiac depressant effects (less effect on heart rate)
*Produce reflex tachycardia by indirectly increasing sympathetic tone
*Primarily work on vascular smooth muscle to reduce PVR
*Increased incidence of peripheral oedema - side effects:
- Peripheral oedema (non-responsive to diuretics
- Hypotension
- Reflex tachycardia and chest pain
- Non-dihydropyridines (target vascular and myocardial cells)
Describe SNS drugs
Adrenoceptors or catecholamines
- Act on adrenoceptors (alpha 1,2 and beta 1,2,3) to cause general physiological changes in the body that prepare for the “fight or flight” response
- 3 pharmacologically significant endogenous catecholamines in the body (all of which are available as therapeutic agents):
- Dopamine – metabolic precursor of noradrenaline and adrenaline
- Noradrenaline – neurotransmitter between sympathetic postganglionic nerves and organs they innervate (adrenergic transmission)
- Adrenaline – hormone secreted by adrenal medulla
- The various adrenorecpetors are pharmacological targets to alter physiological responses by agonism or antagonism.
- Used in acute treatment in an acute setting (for shock etc)
Describe noradrenaline
Released as a result of sympathetic stimulation
- Responsible for peripheral vasoconstriction - mostly due to alpha 1 receptor agonist activity, but can be non-selective to alpha and beta receptors
- Used therapeutically for hypotensive states such as vasodilatory shock (administered intravenously)
Describe adrenaline or epinephrine
- Released as a result of sympathetic stimulation
- Non-selective agonist for all alpha and beta receptors (choice and degree of activity is dose dependent)
- Activity is related to which receptor is being agonised.
- As alpha agonist can cause vasoconstriction
- As beta agonist can increasechronotropy (rate of cardiac contraction) and inotropy (force of contraction) and can be used for low cardiac output (i.e. decompensated cardiac failure)
Describe the mechanism of action of beta blockers
Mechanism of action:
- Competitively block beta receptors in heart, peripheral vasculature, bronchi, pancreas, uterus, kidney, brain and liver.
- Beta-blockers reduce heart rate, BP and cardiac contractility; also depress sinus node rate and slow conduction through the atrioventricular (AV) node, and prolong atrial refractory periods.
- The affinity of individual beta-blockers for beta receptors varies (B1, B2 and B3)
- Beta 1 selective (eg metoprolol, bisoprolol, nebivolol)
- Beta non-selective (eg propranolol)
- Some beta blockers also have alpha blockade (carvediolol and labetalol)
- Some have anti-arrythmic effects through additional potassium channel blockade (eg sotolol)
Indications:
- Myocardial infarction
- Tachyarrhythmias
- Angina
- Chronic heart failure with reduced ejection fraction as part of standard treatment (eg with ACE inhibitor, diuretics)
- Hypertension (not first line)
- Prevention of migraine
- Topical application (eye drops) for glaucoma (eg timolol)
Precautions:
- Consideration of risk v benefit is very important when considering beta blocker treatment.
- Contraindicated in bradycardia (45–50beats/minute), second‑ or third-degree AV block, sick sinus syndrome, severe hypotension or uncontrolled heart failure.Beta-blockers may worsen first-degree AV block
- Asthma:Caution in severe or poorly controlled asthma as they may precipitate bronchospasm.Beta1-selective beta-blockers are preferred for patients with well-controlled asthma (on specialist advice).
- Treatment with drugs that cause bradycardia may further decrease heart rate and cause heart block and hypotension; avoid combination with verapamil (cardioselective CCB)
Side-effects
- cardiovascular: Decreased HR, hypotension, transient worsening of heart failure
- peripheral: cold extremities, exacerbation of Raynaud’s phenomenon
- respiratory: Bronchospasm, dyspnoea
- neurological or endocrine: Depression, fatigue, dizziness, altered glucose and lipid metabolism
recall also class II anti-arrhythmics
Describe diuretics
**
List all
Proximal Tubule:
- Leaky and allows passive flow in either direction – no big concentration gradient
-
Carbonic anhydrase inhibitors are important for Na+ andH+ exchange
- ↑excretion of bicarbonate with accompanying Na+, K+and water, resulting in an increased flow of an alkaline urine →metabolic acidosis
Loop of Henle
- NaCl is actively reabsorbed in the thick ascending limb, causing hypertonicity→watermoves out (tubular fluid becomes more concentrated as it approaches the bend)
- Theascending limbhas very low permeability to water →substantial concentration gradient across the wall of the tubule.
- Active reabsorption of NaCl (not H20)→reducing the osmolality of the tubular fluid and making the interstitial fluid of the medulla hypertonic
- Reabsorption of salt from the thick ascending limb is not balanced by reabsorption of water, so tubular fluid is hypotonic with respect to plasma as it enters the distal convoluted tubule (diluted)
-
Loop diuretics work at thick ascending limb:
- Most potent diuretic class
- InhibitNa+/K+/2Cl−carrier in the lumenal membrane by combining with its Cl−binding site.
- Increase Na+to the distal nephron→loss of H+and K+
- Loss Cl−(not HCO3−) in the urine→ ↑plasmaHCO3− as plasma volume is reduced (metabolic alkalosis)
- Loop diuretics ↑excretion of Ca2+and Mg2+and ↓ excretionof uric acid
Distal tubule
- NaCl reabsorption and impermeability to water, further dilutes the tubular fluid.
- Transport is driven by Na+-K+-ATPase→↓cytoplasmic Na+ →Na+enters the cell down its concentration gradient, accompanied by Cl− via Na+/Cl−co-transporter
- Excretion of Ca2+is regulated in this part of the nephron, byparathyroidhormone(PTH) andcalcitriol→Ca2+reabsorption and phosphate excretion by increasing synthesis of several transporters
- _Thiazide diuretics_ work here
- Inhibits theNa+/Cl−co-transport system bybinding to the Cl−site→natriuresis with loss of sodium and chloride ions in the urine
- Resulting contraction in blood volume stimulates renin secretion, leading to angiotensin formation and aldosterone secretion
Collecting ducts
- Reabsorb Na+and secrete K+and two populations of intercalated cells, α and β, which secrete acid and base, respectively.
- Impermeable to water and cations.
- The movement of ions and water in this segment is under independent hormonal control:
- absorption of NaCl byaldosterone
- absorption of water byantidiuretic hormone(ADH)
-
Aldosterone antagonists
- Compete with aldosterone for its intracellular receptor inhibiting distal Na+retention and K+secretion.
- Limited diuretic activity
- Distal Na+/K+exchange accounts for reabsorption of only 2% of filtered Na+
List some commonly used anti-platelet medications
-P2Y12 antagonists
- Aspirin
- Dipyridamole
- Glycoprotein IIb/IIIa inhibitors
-
Describe P2Y12 antagonsists
(oral):**
- Clopidogrel
- Prasugrel
- Ticagrelor
Mechanism of Action:
- Clopidogrel and Prasugrel: Irreversibly bind to the platelet P2Y12 receptor and inhibit platelet aggregation for the life of the platelet.
- Ticagrelor: Binds reversibly to the P2Y12 receptor.
Indications:
- Clopidogrel, Prasugrel, and Ticagrelor: Acute coronary syndrome (ACS) in combination with aspirin.
- Clopidogrel: Alternative to aspirin for patients (Ticagrelor or Prasugrel arenot).
Adverse Effects:
- Bleeding
- Angioedema (specific to Ticagrelor)
Describe aspirin
- Aspirin (low doses 75-150mg DAILY)
Mechanism of Action: - Aspirin (COX inhibitor): Irreversibly inhibits cyclooxygenase (COX), reducing the synthesis of thromboxane A2 (an inducer of platelet aggregation) for the life of the platelet, thus inhibitig platelet aggregation
Indications:
- Aspirin: PHistory of vascular event/s – secondary prevention of recurrent ischemic stroke and transient ischemic attack (TIA) ^[in combination with an antiplatelet agent?]
Adverse Effects:
- GI irritation
- Bleeding
Describe dipyramidole
Mechanism of Action:
- Inhibits platelet function by inhibiting phosphodiesterase, increasing platelet cAMP, and inhibiting endogenous adenosine reuptake, causing coronary vasodilation.
Indications:
- prevention of recurrent ischaemic stroke and TIA in combo with aspirin
Adverse Effects:
- Headache
- GI upset
- Hot flushes
- Hypotension and tachycardia
Describe glycoprotein IIb/IIIa inhibitors
(intravenous only):
- Tirofiban
- Eptifibatide
Mechanism of Action:
- Prevent binding of fibrinogen to the platelet by occupying the glycoprotein IIb/IIIa receptor, blocking platelet aggregation.
Indications:
- Unstable angina and non-STEMI in high-risk patients
- Percutaneous coronary interventions (PCI)
Adverse Effects:
- Bleeding
- Thrombocytopenia