# Adrenergic Drugs for NEET PG Pharmacology: Adrenaline, Noradrenaline, Dopamine Doses, Dobutamine, Alpha and Beta Blockers

Source: https://tracknation.in/story/adrenergic-drugs-for-neet-pg-pharmacology-adrenaline-noradrenaline-dopamine-doses-dobutamine-alpha-and-beta-blockers (TrackNation — free UPSC notes with PYQs)

> NEET PG Pharmacology: which receptors each catecholamine acts on, adrenaline doses in anaphylaxis, dopamine's dose-dependent effects, dobutamine, phenylephrine and isoprenaline, beta-2 agonists, clonidine, alpha blockers (prazosin, tamsulosin, phenoxybenzamine) and beta blockers (propranolol, metoprolol, atenolol, esmolol, labetalol, carvedilol), all from official drug labels, with a diagram, hooks, MCQs and cards.

## Start Here

🎯 **Exam priority: High.** *Expect vasopressor choices in shock, adrenaline in anaphylaxis, dopamine's dose ranges,
beta-blocker selectivity and contraindications, and alpha-blocker side effects such as first-dose syncope and floppy iris.*

CBME mapping: **PH 2.2** (adrenergic and anti-adrenergic drugs).

## Sympathetic Basics

- Most postganglionic sympathetic fibres release **noradrenaline**. (Sweat glands are the cholinergic exception.)

- Sympathetic activity raises heart rate and contractility, dilates the bronchi and releases glucose from the liver — the
fight-or-flight response that beta and alpha drugs copy or block.

## Agonists: Pressors, Inotropes and Bronchodilators

| **Drug**

 | **Receptors (label)**

 | **Main use (label)**

 | **Remember**

 |
| Adrenaline (epinephrine)

 | Non-selective alpha and beta

 | Anaphylaxis; hypotension in septic shock

 | Raises BP by inotropy, chronotropy and vasoconstriction

 |
| Noradrenaline

 | Alpha (vasoconstriction) + beta (inotropy, coronary dilation)

 | Severe acute hypotension

 | Can cause reflex bradycardia; extravasation → phentolamine

 |
| Dopamine

 | D1/D2, beta-1, alpha-1 by dose

 | Shock (distributive or low output)

 | See the dose diagram; extravasation causes necrosis

 |
| Dobutamine

 | Cardiac beta receptors

 | Short-term inotropic support in cardiac decompensation

 | Does not release noradrenaline (dopamine does)

 |
| Phenylephrine

 | Alpha-1

 | Hypotension from vasodilation during anaesthesia

 | Pure vasoconstrictor

 |
| Isoprenaline (isoproterenol)

 | Non-selective beta; very low alpha

 | Shock; bronchospasm during anaesthesia

 | Diastolic pressure falls

 |
| Salbutamol (albuterol)

 | Beta-2

 | Bronchospasm; exercise-induced bronchospasm

 | Hypokalaemia; paradoxical bronchospasm

 |

**Adrenaline in anaphylaxis**: intramuscular (or subcutaneous) into the **anterolateral thigh**, repeated every
5–10 minutes as needed: **0.3–0.5 mg** for adults and children over 30 kg; **0.01 mg/kg** for children under 30 kg.

## Dopamine Depends on the Dose

*Dopamine infusion: D1/D2 vasodilation below 5 mcg/kg/min, beta-1 inotropy at 5–10, alpha-1 vasoconstriction above 10, as stated in the US dopamine label. Drawn by TrackNation.*

Dopamine barely crosses the blood-brain barrier. Infuse into a large vein: extravasation can cause necrosis.

## Central Alpha-2 Agonist and Alpha Blockers

- **Clonidine**: a centrally acting alpha agonist that lowers blood pressure. Sudden stopping can cause nervousness,
agitation, headache, tremor and a **rapid rise in blood pressure**; patients are told not to stop it without their doctor.

- **Prazosin** (alpha-1 blocker, hypertension): can cause **syncope** with sudden loss of consciousness, usually
from excessive postural hypotension.

- **Tamsulosin**: for **benign prostatic hyperplasia**, not for hypertension. Alpha-1 blockers can cause
**intraoperative floppy iris syndrome** in cataract and glaucoma surgery.

- **Phenoxybenzamine**: long-acting alpha blocker ("chemical sympathectomy") for **phaeochromocytoma**,
to control hypertension and sweating; a beta blocker may be added if tachycardia is excessive.

## Beta Blockers

| **Beta blocker**

 | **Type (label)**

 | **Remember**

 |
| Propranolol

 | Non-selective beta

 | Hypertension, angina, AF rate control, post-MI, migraine prophylaxis, essential tremor, hypertrophic subaortic stenosis, phaeochromocytoma; avoid in asthma

 |
| Metoprolol

 | Beta-1 selective (cardioselective)

 | Selectivity is not absolute: blocks beta-2 at high levels

 |
| Atenolol

 | Beta-1 selective

 | Polar, hydrophilic

 |
| Esmolol

 | Beta-1 selective, IV

 | Half-life about 9 minutes; broken down by red-cell esterases

 |
| Labetalol

 | Alpha-1 + non-selective beta

 | Severe hypertension (IV)

 |
| Carvedilol

 | Alpha + beta

 | Chronic heart failure; post-MI LV dysfunction; hypertension

 |

- **Abrupt withdrawal** of propranolol has caused worsening angina and myocardial infarction: taper over at least a few
weeks.

- Beta blockade can **mask the warning signs of hypoglycaemia** (pulse and pressure changes), especially in
insulin-treated diabetics.

- Propranolol is contraindicated in **bronchial asthma**, sinus bradycardia and heart block greater than first degree.

## Traps the Examiner Sets

- Anaphylaxis: the label's route is IM (or SC) into the anterolateral thigh.

- Dopamine: low dose D1/D2, middle beta-1, high alpha-1.

- Dobutamine does not release noradrenaline; dopamine does.

- Phenylephrine is pure alpha-1; isoprenaline is pure beta (diastolic pressure falls).

- Cardioselective beta-1 blockers lose selectivity at high doses.

- Tamsulosin is for BPH, not hypertension; watch for floppy iris at cataract surgery.

- Phaeochromocytoma: alpha blockade (phenoxybenzamine) first; beta blocker only added for tachycardia.

## Memory Hooks & Shortcuts

*Shortcuts to lock in this article's numbers and lists. Each one only re-packages facts proven above.*

- 🧠 **Dopamine climbs D → β1 → α1** — below 5 dopamine receptors, 5–10 beta-1, above 10 alpha-1 (mcg/kg/min)

- 🧠 **Thigh first, IM first** — anaphylaxis: adrenaline IM into the anterolateral thigh

- 🧠 **Pheo: Alpha before Beta** — phenoxybenzamine first; beta blocker only for tachycardia

- 🧠 **MAE are Mild on lungs** — Metoprolol, Atenolol, Esmolol are beta-1 selective

- 🧠 **Tam for the prostate, floppy for the iris** — tamsulosin: BPH, and intraoperative floppy iris syndrome

- 🧠 **Clonidine Climbs when Cut** — sudden clonidine withdrawal raises blood pressure

## Rapid-Revision Cards

- Non-selective alpha and beta.

- IM thigh; 0.3–0.5 mg (>30 kg) or 0.01 mg/kg; repeat 5–10 min.

- Alpha vasoconstriction + beta inotropy; reflex bradycardia.

- Phentolamine 5–10 mg infiltrated.

- D1/D2: renal, mesenteric, coronary vasodilation.

- Beta-1: rate and contractility.

- Alpha-1: vasoconstriction.

- Cardiac beta; does not release noradrenaline.

- Pure alpha-1; anaesthesia hypotension.

- Pure beta; diastolic pressure falls.

- Hypokalaemia, glucose change, paradoxical bronchospasm.

- Central alpha agonist; rebound hypertension if stopped suddenly.

- Alpha-1 blocker; syncope (postural).

- BPH, not hypertension; floppy iris at cataract surgery.

- Long-acting alpha blocker; phaeochromocytoma.

- Non-selective; migraine prophylaxis, tremor, AF, post-MI; avoid in asthma.

- Metoprolol, atenolol, esmolol; selectivity lost at high doses.

- IV; t½ ~9 min; red-cell esterases.

- Alpha-1 + beta; severe hypertension.

- Alpha + beta; chronic heart failure.

- Masks hypoglycaemia warning signs.

- Angina, MI; taper over weeks.

## Sources

*Facts in this article were checked against these documents.*

- Prescribing labels: epinephrine injection; Levophed (norepinephrine); dopamine HCl injection; dobutamine in dextrose; phenylephrine HCl injection; isoproterenol HCl injection; albuterol HFA; Catapres-TTS (clonidine); prazosin; Flomax (tamsulosin); phenoxybenzamine; propranolol; metoprolol tartrate; Tenormin (atenolol); Brevibloc (esmolol); labetalol injection; Coreg (carvedilol) — DailyMed, US National Library of Medicine, current labels, accessed November 2026 (link)

- MSD Manual Professional Edition: Overview of the Autonomic Nervous System — Merck & Co. (MSD Manuals), 2025 (link)

- Competency Based Undergraduate Curriculum, Pharmacology (PH 2.2) — National Medical Commission, 2024

## Test Yourself: Practice Questions

Twenty-three questions in NEET PG style.

## Practice Questions (NEET PG pattern)

*Original questions written in the style of the exam: +4 for a correct answer, −1 for a wrong one. Every answer
was checked against the sources listed above. NEET PG papers are not published by NBEMS, so these are not past-paper questions.*

**Q1.** For anaphylaxis in an adult, adrenaline (1 mg/mL) is given

- (a) 0.01 mg/kg orally

- (b) 5 mg subcutaneously once

- (c) 1 mg IV bolus as first line

- (d) 0.3–0.5 mg intramuscularly into the anterolateral thigh, repeated every 5–10 minutes as needed

**Answer: (d)** — The label: IM or SC into the anterolateral thigh every 5–10 minutes; 0.3–0.5 mg for adults and children over 30 kg.

**Q2.** The anaphylaxis dose of adrenaline for a child weighing 20 kg is

- (a) 0.5 mg

- (b) 0.1 mg/kg (2 mg)

- (c) 1 mg

- (d) 0.01 mg/kg (0.2 mg)

**Answer: (d)** — Children under 30 kg: 0.01 mg/kg; 20 × 0.01 = 0.2 mg.

**Q3.** Dopamine at 3 mcg/kg/min mainly causes

- (a) renal, mesenteric and coronary vasodilation via D1 and D2 receptors

- (b) alpha-1 vasoconstriction

- (c) marked tachycardia

- (d) beta-2 bronchodilation

**Answer: (a)** — Below 5 mcg/kg/min dopamine activates D1/D2 receptors, causing vasodilation.

**Q4.** At 15 mcg/kg/min, dopamine raises blood pressure mainly through

- (a) muscarinic receptors

- (b) beta-2 receptors

- (c) D1 receptors

- (d) alpha-1 receptors

**Answer: (d)** — Above 10 mcg/kg/min dopamine activates alpha-1 receptors, causing vasoconstriction.

**Q5.** Which inotrope does not release endogenous noradrenaline?

- (a) Ephedrine

- (b) Dopamine

- (c) Dobutamine

- (d) Tyramine

**Answer: (c)** — Dobutamine acts directly on cardiac beta receptors and does not release noradrenaline, unlike dopamine.

**Q6.** Hypotension from vasodilation during anaesthesia is treated with a pure alpha-1 agonist such as

- (a) phenylephrine

- (b) dobutamine

- (c) salbutamol

- (d) isoprenaline

**Answer: (a)** — Phenylephrine is an alpha-1 agonist indicated for hypotension from vasodilation during anaesthesia.

**Q7.** Isoprenaline infusion lowers diastolic pressure because it is

- (a) a non-selective beta agonist with very low alpha affinity

- (b) an alpha-1 agonist

- (c) a D1 agonist

- (d) a beta blocker

**Answer: (a)** — Isoproterenol is a potent nonselective beta agonist; peripheral resistance falls and diastolic pressure falls.

**Q8.** A noradrenaline infusion extravasates. The label's antidote for local infiltration is

- (a) propranolol

- (b) phentolamine

- (c) atropine

- (d) hyaluronidase only

**Answer: (b)** — Infiltrate 5–10 mg phentolamine in 10–15 mL saline.

**Q9.** Noradrenaline can slow the heart through

- (a) direct beta blockade

- (b) D2 activation

- (c) reflex bradycardia from the rise in blood pressure

- (d) muscarinic stimulation

**Answer: (c)** — Overdosage may cause severe hypertension and reflex bradycardia.

**Q10.** An adverse effect listed for inhaled salbutamol (albuterol) is

- (a) bradycardia

- (b) miosis

- (c) hypokalaemia

- (d) hyperkalaemia

**Answer: (c)** — Hypokalaemia and changes in blood glucose may occur; paradoxical bronchospasm is also possible.

**Q11.** Sudden stopping of clonidine can cause

- (a) a rapid rise in blood pressure with agitation and tremor

- (b) bradycardia and hypotension

- (c) hypoglycaemia

- (d) bronchospasm

**Answer: (a)** — Clonidine withdrawal: nervousness, agitation, headache, tremor and a rapid rise in blood pressure.

**Q12.** Syncope with sudden loss of consciousness after starting an antihypertensive is a recognised effect of

- (a) clonidine

- (b) amlodipine

- (c) prazosin

- (d) hydrochlorothiazide

**Answer: (c)** — Prazosin may cause syncope, usually from excessive postural hypotension.

**Q13.** A patient on tamsulosin is listed for cataract surgery. The surgeon should anticipate

- (a) corneal oedema

- (b) acute angle-closure glaucoma

- (c) intraoperative floppy iris syndrome

- (d) malignant hyperthermia

**Answer: (c)** — IFIS has occurred in cataract and glaucoma surgery in patients on or previously on alpha-1 blockers.

**Q14.** Tamsulosin is indicated for

- (a) hypertension

- (b) phaeochromocytoma

- (c) benign prostatic hyperplasia

- (d) Raynaud phenomenon

**Answer: (c)** — Flomax treats BPH symptoms and is not indicated for hypertension.

**Q15.** Hypertension and sweating in phaeochromocytoma are controlled with

- (a) clonidine

- (b) isoprenaline

- (c) propranolol alone

- (d) phenoxybenzamine

**Answer: (d)** — Phenoxybenzamine, a long-acting alpha blocker; add a beta blocker only if tachycardia is excessive.

**Q16.** Propranolol is contraindicated in

- (a) bronchial asthma

- (b) essential tremor

- (c) migraine prophylaxis

- (d) hypertrophic subaortic stenosis

**Answer: (a)** — Contraindications include bronchial asthma, sinus bradycardia and heart block beyond first degree.

**Q17.** Which is a labelled use of propranolol?

- (a) Acute asthma

- (b) Prophylaxis of migraine

- (c) Treating an acute migraine attack

- (d) Hypertensive emergency

**Answer: (b)** — Propranolol prevents common migraine; it is not indicated for an attack in progress or for hypertensive emergencies.

**Q18.** Beta blockers are used cautiously in insulin-treated diabetics because they

- (a) cause ketoacidosis

- (b) cause hyperglycaemic coma

- (c) increase insulin absorption

- (d) mask premonitory signs of hypoglycaemia

**Answer: (d)** — Beta blockade may prevent the pulse and pressure changes that warn of hypoglycaemia.

**Q19.** Stopping propranolol suddenly in a patient with angina can cause

- (a) hypoglycaemia

- (b) worsening angina and myocardial infarction

- (c) asthma

- (d) hypotension

**Answer: (b)** — Taper over at least a few weeks.

**Q20.** Metoprolol at high doses may cause bronchospasm because

- (a) it is an alpha blocker

- (b) it is a muscarinic agonist

- (c) its beta-1 selectivity is not absolute

- (d) it has intrinsic sympathomimetic activity

**Answer: (c)** — Metoprolol is cardioselective, but at higher concentrations it also blocks beta-2 receptors in bronchi.

**Q21.** Esmolol is suited to short-term IV control of heart rate because

- (a) its half-life is about 9 minutes, as red-cell esterases break it down

- (b) it blocks alpha receptors

- (c) it is renally excreted unchanged

- (d) it is a prodrug

**Answer: (a)** — Elimination half-life about 9 minutes; metabolised by red blood cell esterases.

**Q22.** Labetalol differs from propranolol because it also blocks

- (a) alpha-1 receptors

- (b) muscarinic receptors

- (c) beta-3 receptors only

- (d) dopamine receptors

**Answer: (a)** — Labetalol has selective alpha-1 and non-selective beta blocking actions in one molecule.

**Q23.** Which beta blocker with alpha-blocking action is indicated for chronic heart failure?

- (a) Propranolol

- (b) Carvedilol

- (c) Atenolol

- (d) Esmolol

**Answer: (b)** — Carvedilol (an alpha/beta blocker) is indicated for mild-to-severe chronic heart failure.

### Active Recall

From memory: give the receptors and main use of adrenaline, noradrenaline, dopamine (by dose), dobutamine, phenylephrine and isoprenaline; state the adrenaline dose in anaphylaxis; describe clonidine withdrawal; list the uses and side effects of prazosin, tamsulosin and phenoxybenzamine; and compare propranolol, the cardioselective blockers, labetalol and carvedilol.