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General - Pharmacology 💊 > L7: Sympatholytics > Flashcards

L7: Sympatholytics Flashcards

1
Q

What is the classification of Sympatholytics?

A

I- Adrenergic receptor blockers
▪ α- Adrenergic blockers ▪ β- Adrenergic blockers

II- Centrally acting drugs
▪ α-methyl dopa ▪ Clonidine

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2
Q

What is the action of adrenergic blockers?

A

These drugs interact with either α- or β-adrenoceptors to prevent or reverse the actions of endogenously released catecholamines or exogenously administered sympathomimetics

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3
Q

What is the classification of alpha-adrenergic blockers?

A
  1. Non-selective α-receptor blockers: phenoxybenzamine, phentolamine
  2. Selective α1-receptor blockers: prazosin , terazosin, doxazosin
  3. Selective α2-receptor blockers: yohimbine
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4
Q

What are the pharmacological effects of alpha-blockers?

A

 Alpha receptor antagonist drugs lower peripheral vascular resistance (PVR) and blood pressure.
 Hence, postural hypotension and reflex tachycardia are common during the use of these drugs.
 Other minor effects include miosis, nasal stuffiness, etc

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5
Q

What is the mechanism of action of PHENOXYBENZAMINE?

A

Irreversible non-selective α1 & α2 antagonist

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6
Q

What are the uses of PHENOXYBENZAMINE?

A

Pheochromocytoma(with β-blocker)

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7
Q

What are the side effects of PHENOXYBENZAMINE?

A

 Hypotension
 Reflex tachycardia
 Miosis

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8
Q

What are selective alpha 1 blockers?

A

Prazosin, terazosin, doxazosin and tamsulsin

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9
Q

What are the characters of prazosin?

A

 Prazosin is the Prototype drug.

 All of these agents decrease peripheral resistance and lower arterial BP (like most adrenergic blockers) by:

a) α1- receptor blockade.
b) Direct VD of both arterial and venous smooth muscles.

 They cause minimal changes in COP, RBF, and the GFR. (Unlike dopamine)

 They don’t trigger reflex tachycardia by the same degree (as the non-selective blockers.)

 They improve plasma lipid profile and decrease LDL and TGs

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10
Q

What are the therapeutic uses of prazosin?

A

1) Mild to moderate hypertension
2) Benign prostatic hyperplesia (BPH):
▪ reduces the tone of the internal sphincter of the urinary bladder.
3) Raynaud’s syndrome

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11
Q

What are the characters of tamsulosin (more selective)?

A

 is the most commonly used for the treatment of BPH because:

  • It has a high affinity for α1A & α1D, the 2 receptor subtypes responsible for mediating smooth muscle contraction in prostatic tissue.
  • It has little effect on standing BP compared with other α1-blockers. (Like prazosin)
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12
Q

What are the adverse effects of prazosin?

A

▪ First dose hypotension (syncope)
▪ Fluid retention (salt and water retention)
▪ False-positive test for the antinuclear factor of rheumatoid arthritis
▪ α- blockers can worsen incontinence in women with pelvic floor pathology

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13
Q

What are the characters of yohimbine?

A

▪ Selective presynaptic α2-blocker that leads to increased norepinephrine release. (As it prevents negative feedback)

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14
Q

What is yohimbine used for?

A

▪ It is sometimes used as an aphrodisiac (enhance sexual desire) without clinical evidence.

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15
Q

Is pheochromocytoma rare?

A

It is an uncommon cause of hypertension, estimated to occur in approximately 0.1 to 1 % of hypertensive patients.

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16
Q

How is pheochromocytoma treated?

A

▪ Clinical awareness of this tumor should be stressed because:
i. Surgical removal is curative in more than 90 % of patients

ii. Tumor excision has a significant effect on hypertension, the most important cause of pheochromocytoma related mortality and morbidity.

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17
Q

What is the selectivity of beta-blockers related to?

A

The β-receptor–blocking drugs differ in their relative affinities for β1 and β2 receptors; however, the selectivity is dose-related and tends to diminish at higher doses.

18
Q

What are non-selective beta-blockers?

A

“Propran - pindo - timo - sota - Nado”

propranolol, pindolol, timolol, sotalol, nadolol

19
Q

What are cardio-selective beta 1 blockers?

A

“Nebi - biso - meto - ate” “VPPN”

nebiVolol, bisoProlol, metoProlol, ateNolol,

20
Q

What are beta-blockers with additional VD action?

A

“Dileva - Carvedi”

dilevalol, carvedilol

21
Q

How do some beta-blockers cause VD?

A

the VD action comes from either: blocking the vascular α1 receptors; increasing PGE2 and PGI2 synthesis; or by the release of endothelial NO.

22
Q

Pharmacodynamics and chemistry of beta-blockers?

A

 Propranolol is the prototype β-adrenoreceptor antagonist.

 β-blockers are absorbed well after oral administration, many have low bioavailability because of extensive first-pass metabolism.

 Lipophilic β-blockers (e.g. propranolol) can pass readily to the CNS and are cleared by hepatic metabolism. Hydrophilic β-blockers (e.g. atenolol) have limited penetration to the CNS and are excreted primarily by the kidney with little hepatic metabolism.

 β-blockers that undergo hepatic metabolism usually require multiple daily dosing.

 Drugs eliminated via the kidney are suitable for once-daily administration

23
Q

What are the organs affected by beta-blockers?

A
  • CNS
  • Eye
  • CVS
  • Respiratory
  • Sk. Ms.
  • Metabolic effects
  • Specefic properties
24
Q

What are the effects of beta-blockers on CVS?

A

 They block cardiac β1 receptors and decrease all cardiac properties (↓ contractility and COP, ↓ A-V conduction “bradycardia”, ↓ excitability, and automaticity).

 They block the β2-mediated VD in peripheral vessels leading to ↓ blood flow to most tissues.

 They decrease blood pressure through:
a. ↓↓ COP by their –ve inotropic and chronotropic effects.
b. ↓↓ renin release from the kidney (β1).
c. ↓↓ norepinephrine release and central sympathetic outflow
(by blocking presynaptic β2).

25
Q

What are the effects of beta-blockers on the respiratory system?

A

Bronchospasm even with the β1-selective blockers (in high doses)

26
Q

What are the effects of beta-blockers on the eye?

A

Decrease the rate of Aqueous humor production.

27
Q

What are the metabolic effects of beta-blockers?

A

↑aggravation of hypoglycemic effect of insulin

↑ plasma K+ (hyperkalemia) in patients with renal faI lure (mo uptake of k+)

28
Q

What are the effects of beta-blockers on CNS?

A
  1. Antianxiety effects.
  2. Nightmares, vivid dreams, and depression.
  3. Sexual dysfunction through combined central and
    peripheral mechanisms.
29
Q

What are the effects of beta-blockers on Skeletal muscles

A

▪ ↓ essential tremors due to blocking of β2 in skeletal muscles.

30
Q

What is the specific use of propranolol?

A

has local anesthetic (membrane-stabilizing) action i.e. it can inhibit excitability of the cardiac muscle.

31
Q

What is the specific use of pindolol?

A

is a partial agonist i.e. it doesn’t cause excessive bradycardia.

Inc heart rate of alone
Decrease rate with beta agonist

32
Q

What is the specefic use of Elmolol?

A

 is ultrashort acting (t1/2 = 10min) because of extensive hydrolysis by plasma esterases;
 it is administered by i.v. infusion to control arrhythmia during surgery and emergency situations.

33
Q

What is the specefic use of Labetalol?

A

blocks β-receptors and α1-receptors (VD) (mixed blocker).

34
Q

What are the therapeutic uses of beta-blockers?

A 
▪ CVS:
o Hypertension 
o Prophylaxis against angina
o Cardiac arrhythmias (inc rate of atria)
o Myocardial infarction (heart attack)

▪ Thyrotoxicosis

▪ Anxiety states (suppression of the physical manifestations of situational anxiety)

▪ Prophylaxis against migraine attacks

▪ Open angel glaucoma(↓ aqueous humor secretion)

35
Q

What are the adverse effects of beta-blockers?

A

CNS - CSV - Respiratory - GIT - all with masks are tired and aggravated

 CNS: Vivid dreams nightmares and hallucinations

 CVS: Heart failure (low contractility), Heart block (low conductivity), Hypotension, and severe bradycardia

 Respiratory: Bronchospasm

 GIT: nausea, vomiting

 Allergic reaction
 Withdrawal symptoms in case of abrupt discontinuation
 Masking of hypoglycemia in diabetic patients
 Tiredness & fatigue (no k + uptake)
 Aggravation of peripheral ischemia (more VD due to alpha 1)

36
Q

What are the contradictions of beta-blockers?

A

 Absolute contraindications:

a) Bronchial asthma.
b) Any degree of heart block.
c) Sudden withdrawal after long-term use. d) Acute or severe heart failure

 Relative contraindications;

a) Peripheral vascular diseases (PVD). b) Diabetes mellitus.
c) In athletes

37
Q

What is the mechanism of action of alpha methyldopa?

A

 In the CNS, α-methyldopa competes with dopa for dopa decarboxylase enzyme, leading to the formation of α-methylnorepinephrine, (and also α-methyldopamine),
which is a false transmitter.

38
Q

What is an example of centrally acting symapathoplegic drugs?

A

Alpha-methyldopa

39
Q

What are the therapeutic uses of alpha methyldopa?

A

Methyldopa is the drug of choice to treat arterial hypertension in pregnancy

40
Q

What are the adverse effects of alpha methyldopa dopa?

A

“Due to decrease in central sympathetic outflow”

a) Sedation.
b) Nightmares, mental depression
c) +ve Coombs test & autoimmune hemolytic anemia
D) Parkinsonism
E) suicidal activities

General - Pharmacology 💊 (9 decks)

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