Treatment of HTN Flashcards
What is essential HTN?
HTN due to an unknown cause
What is unique about the approval process of drugs for the Rx of HTN?
They require evidence that they are superior to the drugs that proceeded them for use.
What are some distal diuretics?
- Hydrochlorothiazide (HCTZ)
- Metolazone
- Indapamide
What are some loop diuretics?
- Furosemide 2. Torsemide 3. Bumetanide
What are some K+sparing diuretics?
- Triamterene 2. Amiloride
3. Spironolactone 4. Eplenerone
What is a sympatholytic antihypertensive?
Reserpine (peripheral action)
What are some α-blockers?
a. Nonselective: Phenoxybenzamine
b. Selective: Prazosin, Doxazosin, Terazosin
What are some BB’s?
A. Non-selective: Propanolol, Carvedilol, Pindolol, Timolol, Acebutolol, Labetalol
B. Selective: Metoprolol, Atenolol, Betaxolol, Esmolol
C. 3rd Generation: Bisoprolol, Nebivolol
What are the drug classes that have antihypertensive effects?
- Diuretics
- Agents affecting SNS
- Agents interfering w/ RAS
- L-type CCBs
- Direct Vasodilators
- Centrally-acting α2-agonists
- Endothelin Receptor Blockers
What are the types of diuretics useful in the Rx of HTN?
- Distal
- Loop
- K-sparing
What types of agents affecting the SNS are useful in the Rx of HTN?
- Sympatholytic
- α-blockers
- BB’s
What types of agents that interfere with the renin-angiotensin activity are useful in the Rx of HTN?
- ACEi’s
- ARB’s
- Renin inhibitors
What are the ACEi’s?
the PRILs
- Captopril
- Lisinopril
- Enalapril
- Ramipril
What are the ARB’s?
the SARTANs
- Losartan 2. Valsartan 3. Irbesartan
- Candesartan 5. Telmisartan
What is the drug that acts as a renin inhibitor?
Aliskerin
What are the two groups of L-type CCB’s?
- Verapamil and Diltiazem
2. The PINEs: Amlodipine, Nifedipine, Nicardipine Nimodipine
What are the direct vasodilators?
- Minoxidil
- Sodium Nitroprusside
- Diazoxide
- Fenoldopam
What are the centrally acting α2-agonists?
Clonidine, Guanabenz, Guanfacine, Methyldopa
What is the drug that acts as an endothelin receptor blocker?
Bosentan
What is normal BP? Pre-HTN? Stage 1 HTN? Stage 2 HTN?
Normal:160/>100
Do you start Rx for HTN during the pre-HTN stage?
No, during pre-HTN, you monitor the patient and tell them to modify their diet, particularly to reduce their salt intake. Treatment does not begin until Stage 1 HTN.
Even though we do not know the specific cause of essential HTN, we treat it anyway. Why?
B/c HTN has a straight-forward route to the development of CHF, stroke, and organ failure, and by treating it, you can help prevent these things.
What are the organs involved in the regulation of BP?
heart, kidneys, and blood vessels
The tone of resistance (arterioles) and capacitance (veins) blood vessels is regulated by what three things? What is their effect?
- SNS exerts its control via a barometric reflex: vasoconstriction or increase HR/contractility
- RAAS: vasoconstriction and hypervolemia (Na and water retention)
- Local release of hormones (Endothelin, NO, kinins, etc)
How does the SNS affect/regulate BP? On what organs does it act on?
- It acts on the heart to increase the HR and the force of myocardial contraction.
- It acts on the kidney to increase the production/release of Renin (RAAS).
- It acts on the resistance vessels, which are precapillary arterioles to produce rapid vasoconstriction. It also acts on the veins, thereby preventing the pooling of blood and returning it to the heart faster.
How does the RAAS regulate/affect BP? How quickly?
In general, this is a slower acting system, but it has both fast actions and slower actions.
- Fast Action: Production of ANGII, the most powerful vasopressor/constrictor in the body. ANGII is also acts on the PCT to increase reabsorption of NaCl and water, leading to hypervolemia and an increase in BP.
- Slower Action: ANGII acts on adrenal cortex to increase production of aldosterone, which stimulates reabsorption of Na+ and excretion of K+.
How does the release of local hormones factor into the regulation of BP? Examples?
The locally released hormones, such as bradykinin and other kinins and NO cause vasodilation and a decreased in BP. While others such as endothelin, cause vasoconstriction and an increase in BP.
What is the nt of the SNS? What receptors does it act on?
Norepinephrine (NE); it acts on α and β receptors.
What type of receptor are α1-R’s and ANGII-R’s? What is net result of activating this type of receptor?
They are coupled to Gq proteins. The net result is increased intracellular Ca2+ causing contraction of smooth muscle cells, and vasoconstriction of vessels.
How does activation of a Gq-coupled receptor lead to increased intracellular Ca2+ concentration? What does the increased Ca2+ then cause? (aka what is the result of SNS stimulation of vessels)
Gq activation→Phospholipase C activation→cleavage of PIP2 into DAG and IP3→ IP3 acts on IP3-R’s of SR→release of Ca2+ from SR into the cell→smooth muscle cell contraction→vasoconstriction
What is the currency smooth muscle cell tone?
Ca2+: As [Ca2+] increases, there is more vasoconstriction
What type of adrenergic receptors are located in the heart?
β-R’s, primarily β1’s
What type of receptor are the β-R’s?
They are coupled to Gs proteins
What happens in the cardiac cells when activation of the β-R’s results in Gs activation? (aka what is the result of SNS stimulation of the heart?)
Gs activation→activation of adenylate cyclase (AC)→increased production of cAMP from ATP→cAMP activates PKA→phosphorylation of L-type Ca2+ Channels (L-tCCs)→increased entry of extracellular Ca2+ into heart cells→increased force of myocardial contraction and increased HR
What type of effects does SNS have? What receptors does it signal thru? What is the mechanism of these receptors?
The SNS has both excitatory and inhibitory effects.
It signals thru two major GPCRS (metabotropic):
α and β adrenergic receptors
How are α and β-mediated responses accomplished? Where?
- α1 responses occur in blood vessels are due to Ca2+
- Centrally located α2 responses inhibit the vasomotor center (RVLM)
- β responses are due to cAMP, the heart is the major site
What are the two main nt’s of the SNS? Where are they released from? What type of transmission are they involved in?
NE is the nt released from postganglionic sympathetic nerve terminals. While E is made in the adrenal medulla and enters the blood stream, where it acts as the circulating arm of the catecholamines/SNS.
This is adrenergic transmission.
On what receptors does NE act and where? Result?
- β1’s in the heart (not on β2’s in lungs or vessels), where it increases force of myocardial contraction, HR, and the rate of relaxation of heart muscle. Net result: pumps more volume at higher rate.
- It acts primarily on α1’s of blood vessels, causing vasoconstriction of arterioles and venules.
- α2’s on presynaptic terminal membrane, inhibiting the further release of NE.
How are catecholamines (Dopamine, NE, E) made?
Tyrosine is transported into presynaptic terminal→tyrosine hydroxylase converts it to DOPA→Dopamine (transported into vesicle by VMAT aka Uptake2)→NE→E
What antihypertensive is an adrenergic neuron blocker (ANB) aka peripheral sympatholytic?
Reserpine
What is the mechanism of action of Reserpine?
It inhibits Uptake2 (VMAT), which transports NE/dopamine into presynaptic vesicles, so it prevents the packaging of NE into vesicles→depletion of NE and 5-HT from neurons and depletion of E from adrenal gland
What is the net effect of Rx with reserpine?
Depletion of NE/E→decreased NE/E release→decreased sympathetic tone→reduced TPR, CO, Renin release, and BP
What is the clinical use of Reserpine?
Reserpine is used orally for mild to moderate HTN
What are the side effects and contraindications of Reserpine?
- Mostly CNS Effects: sedation, mental depression, bad dreams. Do NOT give to someone w/ history mental depression (INCREASES SUICIDAL TENDENCIES)
- Increased incidence of duodenal and gastric ulcers, and is contraindicated in pt’s w/ PUD or ulcerative colitis
What are the three prototypical α1-blocker agents?
the OSINs or AZOSINs
- Prazosin
- Doxazosin
- Terazosin
How does NE generate vasoconstriction thru α1-R’s? Where are α1’s located?
NE binds α1-R→Gq activation→PLC→PIP2 to DAG and IP3→IP3 releases Ca2+ from SR→sm m contraction→vasoconstriction
α1’s are located in arterioles and a little bit in veins
What is the mechanism of action of α1-blockers?
They block peripheral α1-R’s in arterioles and venules, causing vasodilation, which reduces TPR and BP.
What is the pharmacologic effects of α1-blockers?
- Decrease TPR and BP
- Relieve symptoms of BPH by relaxing bladder and prostate muscles
- Increase HDL-C and lower LDL-C, and also have a beneficial effect on insulin resistance
What is the clinical use of Prazosin?
Mainly used as an antihypertensive
What is the clinical use of Terazosin and Doxazosin?
They are the preferred drug of older for older men w/ BPH and HTN who are otherwise healthy
What are the side effects of α1-blockers?
- First dose hypotension (faint when try to stand up; goes away w/ time), esp w/ PRAZOSIN, so give them at bed time
- Dizziness and vertrigo, drowsiness, palpitations
What are the nonspecific α-blockers? Mech of action? Clinical Use?
Phentolamine, Phenoxybenzamine. They block both α1 and α2-R’s.
Used to control HTN in pt’s w/ Pheochromocytoma (prevention of hypertensive crisis due to NE excess)
What are four important parameters to pay attention to w/ BB’s?
- Intrinsic sympathomimetic activity (ISA)
- Membrane Stabilizing Activity (MSA)
- Cardioselectivity (β1-selectivity)
- Lipid Solubility
What does it mean if a BB has ISA?
The drug binds to the β1-receptor and blocks it, but somehow it activates it a little bit. This ISA is referred to as partial antagonist or an antagonist partial agonist activity.
What is a BB with ISA? What is BB that is pure antagonist with no ISA?
ISA: Pindolol
No ISA: Propanolol
What is a BB with high MSA? What is MSA associated with?
Propanolol (most of the others have low MSA).
MSA is related to the anti-arrhythmic activity of the drug. If it stabilizes the neuronal membrane, then it prevents the spread of currents involved in arrhythmias.
What is cardioselectivity? Why is it important to consider cardioselectivity when giving a patient a BB?
Cardioselectivity refers to BB’s that have specificity for β1’s in the heart over β2’s in the lungs. BB’s can be β1-selective or nonselective (act on β1 and β2). A nonselective BB can block β2’s in the lungs and cause difficulty breathing, so they should be avoided w/ asthma/COPD.
Why is lipid solubility of BB’s important?
The more lipid-soluble they are, the easier they can cross the BBB and enter the CNS.
What are some nonselective BBs? What are some β1-selective BBs?
Nonselective: Propanolol, Timolol, Pindolol
Selective: Metropolol, Atenolol
What is the mechanism of action of BB’s with no ISA? (4)
a. They block myocardial β1-R’s→decrease HR, contractility, and CO
b. All but Pindolol lock β1-R’s in JGA of kidney→inhibit renin release
c. Reduced central sympathetic outflow (unless low lipid solubility)
d. Decreased release of peripheral NE by blocking presynaptic β-R’s
Due to their actions in the kidney, BB’s are especially useful in lowering BP in what type of patients?
Patients w/ high renin HTN (but they do work in patients with normal to low renin)
(low renin HTN is volume-dep HTN)
What is the result of chronic use of BB?
- Decrease CO
- Decrease peripheral resistance
- Decrease arterial pressure
Other than the extended actions of 3rd-generation BBs, how do 1st and 2nd generation BBs differ from those of the 3rd generation?
1st and 2nd generation BBs have more side effects in general and they have more metabolic side effects than the 3rd generation.
What are BB’s effective in treating?
All grades of HTN.
Are BBs more effective in high-renin or low-renin HTN?
They are more effective in high renin HTN (easier to tx; in young and caucasians) b/c they lower renin levels. They still work in low-renin HTN (hard to tx; in elderly and african americans) but are less effective.
The antihypertensive effect of BBs is additive when given in combination w/ what drug? Why? Does it have to be given w/ this drug?
BBs do not cause retention salt and water and can be administered w/out a diuretic. However, their anti-hypertensive effect is additive w/ a diuretic.
What are the compelling indications for the use of a BB (aka BB is the preferred choice of tx)?
- Highly preferred in hypertensive pt’s w/ conditions such as MI, ischemic heart disease (IHD), or CHF.
- Preferred in hypertensive pt’s w/ hyperthyroidism and migraines. (b/c BB’s protect the heart from the effect of thyroid hormone).
What are some additional uses of BB’s in general? (4) What are two of their off-labeled uses? (2)
- CHF: decreased mortality in patients w/ HF, so esp useful in those patients who also have HTN.
- MI: useful in preventing 2nd MI in pt’s w/ IHD by causing bradycardia.
- Sinus and AV arrhythmias
- Open angle glaucoma: given as eyedrop to reduce production of aqueous humor.
Off-labeled uses: - Stage fright
- To erase memories of horror
Which BB’s are associated w/ reduced mortality in CHF?
- CARVEDILOL
- Metropolol-XL
- Bisoprolol
What is the effect of propanolol? What is useful as? Why?
It’s a nonspecific BB that produces bradycardia and decreases HR during exercise→Hypotension.
B/c of its MSA, it’s useful as an antiarrhythmic.
In what type of pt is the use of Propanolol contraindicated in? Why?
Asthmatics. B/c it’s not cardioselective, it causes bronchospasm.
How should propanolol be discontinued when it’s no longer needed for a patient? Why?
Withdraw it slowly to prevent reflex tachycardia, as chronic blockage of the β-R’s led to increased density (upregulation) that can now be activated by NE.
What are the two most cardioselective BBs?
Metropolol and Atenolol
What is important about Bisoprolol?
a. Long acting β1-specific (only have to take it once a day)
b. Commonly used bc decreases ALL cases of mortality
c. As eye drops for glaucoma
What is the selectivity/activity of Pindolol and Acebutolol? What does this result in?
They are non-selective BB’s w/ partial agonist activity (ISA). Thus, they reduce CO and HR less than other BBs
What is important about the PK’s of Esmolol? How is it used and for what?
It is β1-selective w/ a very short half-life (8 min); given IV for management of tachycardia, arrhythmias during surgery and postoperative tachycardia caused by HALOTHANE ANESTHETIC.
Timolol (and 5 other BB’s) has what type of selectivity? What is it used for?
Non-selective BB used as eye drops for Rx of chronic open angle glaucoma.
What are the side effects of 1st and 2nd generation BB’s? (7)
- Cold Extremities
- Bradycardia (sometimes this is the desired effect but can be in excess)
- Bronchospasm
- CNS side effects
- Metabolic effects
- Drug withdrawal syndrome
- Others (fatigue, decreased exercise tolerance, impotence)
Why do BB’s cause cold extremities? What happens in this respect w/ prolonged BB use?
Unopposed α-mediated action constricts blood vessels in the skin and limits blood flow, causing cold extremities.
Prolong use worsens peripheral arterial insufficiency and can cause Raynaud’s Phenomenon
What effect of BB’s leads to bradycardia? What type of drugs are contraindicated w/ BB’s?
Decreased AV nodal conduction.
Contraindicated w/ Verapamil and Diltiazem, which also slow AV nodal conduction