Sympatholytic Drugs
# ✅ **1. CLASSIFICATION (Gold Standard)**
## **A. Adrenergic Receptor Blockers**
### **1) α-Blockers**
#### **Non-selective α1 + α2**
* **Phenoxybenzamine** (irreversible)
* **Phentolamine** (reversible)
#### **Selective α1-blockers**
* **Prazosin**
* **Terazosin**
* **Doxazosin**
* **Tamsulosin**
* **Alfuzosin**
* **Silodosin**
### **2) β-Blockers**
#### **Non-selective (β1 + β2)**
* Propranolol
* Nadolol
* Timolol
* Pindolol (ISA)
* Sotalol (also class III antiarrhythmic)
#### **Cardioselective (β1-selective)**
* Metoprolol
* Atenolol
* Esmolol
* Bisoprolol
* Betaxolol
#### **β-blockers with ISA**
* Pindolol
* Acebutolol
#### **β + α1 blockers**
* Labetalol
* Carvedilol
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## **B. Neuron Blocking Agents**
* **Reserpine** – depletes monoamines (NE, DA, 5HT)
* **Guanethidine** – inhibits NE release
* **Guanadrel**
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## **C. Central Sympatholytics (α2-agonists causing ↓ SNS outflow)**
* **Clonidine**
* **Methyldopa**
* **Guanfacine**
* **Tizanidine**
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# ⭐ **2. MECHANISM OF ACTION (High-Yield)**
### **α-blockers**
* **α1-block** → vasodilation → ↓ BP
* **α2-block (non-selective)** → ↑ NE release → reflex tachycardia (seen with phentolamine/phenoxybenzamine)
### **β-blockers**
* **β1 block** → ↓ HR, ↓ contractility, ↓ renin
* **β2 block** → bronchoconstriction, ↑ PVR
* **ISA** → partial agonist activity → less bradycardia
### **Central α2-agonists**
* Stimulate α2 receptors in brain → ↓ sympathetic outflow → ↓ HR & BP
### **Neuron blockers**
* Prevent NE storage/release → profound sympatholysis
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# ⭐ **3. CLINICAL USES**
### **α-blockers**
#### **Prazosin group**
* **Hypertension**
* **BPH (Tamsulosin best)**
* **Raynaud's disease**
* **PTSD nightmares (Prazosin)**
#### **Phenoxybenzamine/Phentolamine**
* **Pheochromocytoma** (pre-op)
* **Cocaine toxicity (phentolamine)**
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### **β-blockers**
#### **Cardiac**
* **Hypertension**
* **Angina**
* **MI secondary prevention**
* **Arrhythmias (Esmolol, Sotalol)**
* **CHF (Carvedilol, Metoprolol succinate, Bisoprolol)**
#### **Other**
* **Thyrotoxicosis**
* **Migraine prophylaxis**
* **Glaucoma (Timolol)**
* **Portal hypertension (Propranolol, Nadolol)**
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### **Central sympatholytics**
* **Clonidine withdrawal HTN**
* **ADHD (Guanfacine)**
* **Hypertensive emergency (Clonidine)**
* **Pregnancy HTN (Methyldopa)**
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### **Neuron blockers**
* Rarely used due to side effects
* Severe HTN refractory cases
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# ⭐ **4. ADVERSE EFFECTS (COMPLETE)**
## **α-blockers**
* **First-dose hypotension**
* Reflex tachycardia
* Nasal congestion
* Sexual dysfunction
* Orthostatic hypotension
## **β-blockers**
* Bradycardia
* Heart block
* Bronchospasm (in asthmatics)
* Masked hypoglycemia
* Cold extremities
* Depression
* Erectile dysfunction
## **Central α2 agonists**
* Rebound hypertension (Clonidine)
* Sedation
* Dry mouth
* Hemolytic anemia (Methyldopa)
## **Neuron blockers**
* Severe depression (Reserpine)
* Orthostatic hypotension
* Sodium & water retention
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# ⭐ **5. CONTRAINDICATIONS**
## **α-blockers**
* Hypotension
* Volume depletion
## **β-blockers**
* Asthma/COPD (non-selective)
* Bradycardia
* Heart block
* Acute decompensated HF
## **Central α2 agonists**
* Depression
* Recent MI (Clonidine withdrawal risk)
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# ⭐ **6. IMPORTANT DRUG–DRUG INTERACTIONS**
* β-blockers + CCBs (verapamil/diltiazem) → **severe bradycardia**
* β-blockers + insulin → **masked hypoglycemia**
* α-blockers + PDE-5 inhibitors → **profound hypotension**
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# ⭐ **7. SPECIAL NOTES FOR NEETPG**
### **Prazosin → first dose syncope**
### **Phenoxybenzamine → irreversible**
### **Esmolol → shortest acting**
### **Timolol → glaucoma**
### **Carvedilol → CHF survival benefit**
### **Methyldopa → pregnancy HTN**
### **Clonidine withdrawal → rebound HTN**
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# ⭐ **8. TAGS**
sympatholytic drugs, alpha blockers, beta blockers, clonidine, methyldopa, prazosin, propranolol, adrenergic blockers, pharmacology, hypertension drugs, BPH drugs, NEETPG pharmacology, autonomic nervous system, sympatholytics
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## **1️⃣ Case 1 — Pheochromocytoma Pre-operative**
A 32-year-old woman with episodic headache, palpitations, and sweating has BP **210/120 mmHg**. Plasma metanephrines ↑. Before surgery, she is started on a drug that *irreversibly* blocks α-receptors.
**Drug?** Phenoxybenzamine
**Why?** Prevents intra-op catecholamine surges.
**Teaching point:** *α-block BEFORE β-block.*
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## **2️⃣ Case 2 — Cocaine-Induced Chest Pain**
A 29-year-old male presents with severe chest pain after cocaine use. BP 190/110.
Avoid β-blockers (unopposed α).
**Drug of choice:** Phentolamine (α-blocker).
**Effect:** BP reduction without worsening vasospasm.
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## **3️⃣ Case 3 — First-Dose Syncope**
A 55-year-old man with BPH and HTN is started on Prazosin. After first dose, he collapses.
**Cause:** First-dose orthostatic hypotension.
**Fix:** Start at bedtime; titrate slowly.
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## **4️⃣ Case 4 — BPH with Severe LUTS**
A 67-year-old man with dribbling, weak stream, nocturia.
**Drug:** Tamsulosin (α1A selective).
**Why:** Relaxes prostate/bladder neck with minimal BP drop.
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## **5️⃣ Case 5 — Raynaud Phenomenon**
Young woman with cold, painful fingers during winter.
**Drug:** Prazosin
**Why:** α1-block → improves digital blood flow.
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## **6️⃣ Case 6 — Portal Hypertension**
A patient with cirrhosis presents with variceal bleeding prophylaxis need.
**Drug:** Propranolol or Nadolol (non-selective β-block).
**Mechanism:** β1-block ↓ CO; β2-block → ↑ splanchnic vasoconstriction → ↓ portal pressure.
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## **7️⃣ Case 7 — Thyroid Storm**
A 34-year-old with severe thyrotoxicosis. HR 160/min, tremors, fever.
**Drug:** Propranolol
**Why:** Blocks β-symptoms + reduces peripheral T4 → T3 conversion.
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## **8️⃣ Case 8 — Acute Aortic Dissection**
A 49-year-old hypertensive presents with tearing chest pain.
Goal: ↓ HR & BP simultaneously.
**Drug:** IV Esmolol
**Reason:** Ultra-short acting, easy titration.
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## **9️⃣ Case 9 — MI Secondary Prevention**
Post-MI day 3. Stable.
**Drug:** Metoprolol / Bisoprolol
**Outcome:** ↓ mortality, ↓ arrhythmias.
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## **🔟 Case 10 — Glaucoma**
A 52-year-old man with open-angle glaucoma.
**Drug:** Timolol eye drops
**Mechanism:** ↓ aqueous humor production.
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## **1️⃣1️⃣ Case 11 — SVT Control**
A 27-year-old with PSVT, HR 180/min.
**Drug:** Esmolol
**Why:** Rapid onset/offset, good for acute control.
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## **1️⃣2️⃣ Case 12 — Migraine Prophylaxis**
Young female with repetitive severe migraines.
**Drug:** Propranolol
**Why:** Central β-block → prevents attacks.
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## **1️⃣3️⃣ Case 13 — Chronic Heart Failure**
A 62-year-old man with EF 30%, NYHA II.
**Drug:** Carvedilol or Metoprolol succinate
**Effect:** ↓ mortality; prevents remodeling.
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## **1️⃣4️⃣ Case 14 — Resistant Hypertension**
A patient has uncontrolled BP despite ACEI + CCB + Thiazide.
**Drug:** Clonidine
**Mechanism:** Central α2 agonist → ↓ SNS outflow.
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## **1️⃣5️⃣ Case 15 — Pregnancy-Induced Hypertension**
A 28-year-old pregnant woman with BP 150/98 at 28 weeks.
**Drug:** Methyldopa
**Why:** Safest central sympatholytic in pregnancy.
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## **1️⃣6️⃣ Case 16 — ADHD in Children**
A 10-year-old with inattention and hyperactivity, unresponsive to stimulants.
**Drug:** Guanfacine
**Mechanism:** Central α2-agonist.
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## **1️⃣7️⃣ Case 17 — Clonidine Withdrawal Crisis**
A patient abruptly stops clonidine. Presents with BP **220/120**, tremors, tachycardia.
**Diagnosis:** Clonidine withdrawal hypertension.
**Management:** Restart clonidine + β-blocker cautiously.
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## **1️⃣8️⃣ Case 18 — Orthostatic Hypotension**
A 65-year-old diabetic on Prazosin. Presents with dizziness on standing.
**Cause:** α1-block → impaired vasoconstriction.
**Management:** Dose reduction; bedtime dosing.
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## **1️⃣9️⃣ Case 19 — Depression After Old Antihypertensive**
A 72-year-old on Reserpine develops severe depression.
**Reason:** Depletion of monoamines (NE, 5HT, DA)
**Action:** Stop drug; switch therapy.
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## **2️⃣0️⃣ Case 20 — Asthma Attack on Propranolol**
A 40-year-old asthmatic was started on propranolol for migraine. Now presents with wheezing.
**Reason:** β2-block → bronchoconstriction.
**Safer alternative:** Metoprolol (β1-selective).
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## **2️⃣1️⃣ Case 21 — Hypertensive Emergency in CNS Damage**
A patient with subarachnoid hemorrhage has BP 200/118.
**Drug:** Labetalol (α1 + β-blocker)
**Why:** Balanced BP reduction without large HR change.
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## **2️⃣2️⃣ Case 22 — Postural Tachycardia Syndrome (POTS)**
A 22-year-old female with palpitations on standing.
**Drug:** Propranolol (low dose)
**Effect:** Controls excessive sympathetic response.
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## **2️⃣3️⃣ Case 23 — Stress-Induced Sweating & Tremor**
A student with anxiety, tremor before presenting thesis.
**Drug:** Propranolol
**Mechanism:** β-block prevents peripheral adrenergic symptoms.
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## **2️⃣4️⃣ Case 24 — Hypertrophic Cardiomyopathy**
A young athlete with murmur increases on standing.
**Drug:** β-blockers (e.g., Metoprolol)
**Why:** ↓ HR → ↑ filling → ↓ obstruction.
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## **2️⃣5️⃣ Case 25 — Severe Autonomic Hyperactivity in Alcohol Withdrawal**
A 37-year-old alcoholic in withdrawal shows severe tachycardia, HTN, tremors.
α2-agonist helps calm sympathetic storm.
**Drug:** Clonidine (as adjunct)
**Benefit:** Controls sympathetic overactivity.
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# ⭐ **SYMPATHOLYTIC DRUGS — USES, ADVERSE EFFECTS, CONTRAINDICATIONS**
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# ✅ **1. α-BLOCKERS**
## **A. Non-selective α1 + α2 blockers**
### **Drugs**
* **Phenoxybenzamine**
* **Phentolamine**
### **Uses**
* **Pheochromocytoma (pre-operative)**
* Hypertensive crisis (cocaine toxicity, MAOI-tyramine reaction)
* Raynaud phenomenon (less preferred)
### **Adverse Effects**
* Severe **orthostatic hypotension**
* **Reflex tachycardia** (due to α2 block ↑ NE release)
* Nasal congestion
* Miosis
* GI hypermotility
### **Contraindications**
* Coronary artery disease (tachycardia worsens ischemia)
* Volume depletion
* Heart failure (due to reflex tachycardia)
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## **B. Selective α1 blockers**
### **Drugs**
* Prazosin
* Doxazosin
* Terazosin
* **Tamsulosin, Alfuzosin** (α1A selective)
### **Uses**
* **Hypertension**
* **Benign Prostatic Hyperplasia (BPH)**
* *Tamsulosin*: best for urinary flow
* Raynaud syndrome
* PTSD nightmares (Prazosin)
### **Adverse Effects**
* **First-dose syncope** (Prazosin classically)
* Postural hypotension
* Dizziness
* Headache
* Fatigue
* Sexual dysfunction
* Nasal congestion
### **Contraindications**
* Hypotension
* Cataract surgery risk of floppy-iris syndrome (especially Tamsulosin)
* Severe hepatic impairment
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# ✅ **2. β-BLOCKERS**
## **A. Non-selective (β1 + β2)**
### **Drugs**
* Propranolol
* Nadolol
* Timolol
* Pindolol
* Sotalol
### **Uses**
* Hypertension
* Angina
* MI prophylaxis
* Arrhythmias (Sotalol also Class III antiarrhythmic)
* **Thyrotoxicosis**
* Migraine prophylaxis
* **Portal hypertension**
* Glaucoma (Timolol)
### **Adverse Effects**
* **Bronchospasm** (dangerous in asthma/COPD)
* Bradycardia
* AV block
* Hypoglycemia masking
* Fatigue
* Cold extremities
* Erectile dysfunction
* Depression (propranolol)
### **Contraindications**
* Asthma, COPD (non-selective worsen bronchospasm)
* Bradycardia
* Heart block (2nd/3rd degree)
* Acute decompensated heart failure
* Severe peripheral vascular disease
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## **B. Cardioselective (β1-selective)**
### **Drugs**
* Metoprolol
* Atenolol
* Bisoprolol
* Esmolol
* Betaxolol
### **Uses**
* Hypertension
* Chronic heart failure (Metoprolol, Bisoprolol)
* Post-MI
* Stable angina
* SVT rate control
* Glaucoma (Betaxolol)
### **Adverse Effects**
* Bradycardia
* Heart block
* Fatigue
* Dizziness
* Reduced exercise tolerance
### **Contraindications**
* Severe bradycardia
* AV conduction blocks
* Cardiogenic shock
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## **C. β-Blockers with ISA (Intrinsic Sympathomimetic Activity)**
### **Drugs**
* Pindolol
* Acebutolol
### **Uses**
* HTN in patients prone to bradycardia
* Patients with mild asthma (still caution)
### **Adverse Effects**
* Less bradycardia but same β2 risks
* Palpitations
* CNS disturbances
### **Contraindications**
* MI/post-MI (ISA reduces protective effect)
* Heart failure (not beneficial)
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## **D. Combined α1 + β blockers**
### **Drugs**
* Labetalol
* Carvedilol
### **Uses**
* **Hypertensive emergencies (Labetalol)**
* Chronic heart failure (Carvedilol: mortality benefit)
* Hypertension in pregnancy (labetalol)
### **Adverse Effects**
* Orthostatic hypotension
* Bradycardia
* Fatigue
* Bronchospasm
* Liver enzyme elevation (Carvedilol rare)
### **Contraindications**
* Asthma/COPD
* Bradycardia
* Heart block
* Cardiogenic shock
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# ✅ **3. CENTRAL SYMPATHOLYTICS (α2-agonists)**
## **Drugs**
* Clonidine
* Methyldopa
* Guanfacine
* Tizanidine
### **Uses**
* Resistant hypertension
* Hypertensive urgency (Clonidine)
* Pregnancy hypertension (Methyldopa)
* ADHD (Guanfacine)
* Muscle spasticity (Tizanidine)
* Opioid/alcohol withdrawal (Clonidine)
### **Adverse Effects**
* **Sedation**
* Dry mouth
* **Rebound hypertension** (if clonidine abruptly withdrawn)
* Depression
* Edema
* Hemolytic anemia (Methyldopa)
* Hepatotoxicity (Methyldopa)
### **Contraindications**
* Depression
* Active liver disease (Methyldopa)
* Recent MI (clonidine rebound risk)
* Elderly with high fall risk
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# ✅ **4. NEURON BLOCKERS**
## **Drugs**
* Reserpine
* Guanethidine
* Guanadrel
### **Uses**
* Rare now
* Severe refractory hypertension
### **Adverse Effects**
* **Severe depression** (Reserpine depletes serotonin & NE)
* Nasal congestion
* Orthostatic hypotension
* Diarrhea
* Peptic ulcer aggravation
### **Contraindications**
* Depression or suicidal risk
* Peptic ulcer
* Parkinsonism (dopamine depletion worsens symptoms)
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