Drugs Acting on Autonomic Nervous System (P. Chemistry | Ch-6) – D Pharma 1st year Notes

If you are a D.Pharm student looking for complete notes on drugs acting on the autonomic nervous system, you have landed on the right page. This master guide covers every drug in the Chapter 6 syllabus — from sympathomimetics to anticholinergics — with IUPAC names, mechanisms of action, uses, side effects, and brand names, exactly as required for your D.Pharm first year pharmaceutical chemistry examination.

This page is your complete index. Each section links to a detailed post covering that drug category in full. Bookmark this page and use it as your Chapter 6 revision hub.

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What is the Autonomic Nervous System?

The autonomic nervous system (ANS) controls all the involuntary functions of the body — heart rate, blood pressure, digestion, breathing, sweating, and glandular secretions. Unlike voluntary muscles which we consciously control, the ANS works automatically, 24 hours a day, keeping the body in balance.

The ANS has two divisions that work in opposite directions:

Sympathetic nervous system activates the body during stress or danger — increases heart rate, raises blood pressure, dilates bronchi, and diverts blood to muscles. This is the “fight or flight” response triggered by norepinephrine and epinephrine.

Parasympathetic nervous system returns the body to rest after a stressor — slows the heart, stimulates digestion, constricts the pupils, and increases secretions. This is the “rest and digest” response controlled by acetylcholine.

Drugs acting on the ANS either mimic or block these two neurotransmitter systems. Understanding which receptor a drug targets tells you exactly what it will do in the body — and what side effects to expect.

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Why This Chapter is Important for D.Pharm Exams

Chapter 6 is one of the highest-scoring chapters in D.Pharm first year pharmaceutical chemistry. Questions from this chapter appear every year in university examinations in multiple formats:

• IUPAC names and chemical structures of starred compounds
• Mechanism of action of individual drug classes
• Differences between drug categories (e.g., direct vs indirect sympathomimetics)
• Uses, side effects, and brand names
• Short notes on specific drugs
• Long answer questions on drug classes like beta blockers, anticholinergics

Every drug in this chapter follows the same pattern in exam questions — IUPAC name, chemical structure, classification, mechanism, uses, stability, formulations, and brand names. Our detailed posts cover all of these systematically.

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Complete Drug List — Chapter 6 Syllabus

Sympathomimetic Agents (Adrenergic Agonists)

• Direct Acting: Nor-epinephrine, Phenylephrine, Terbutaline, Naphazoline, Epinephrine, Dopamine, Salbutamol, Tetrahydrozoline
• Indirect Acting: Hydroxyamphetamine, Pseudoephedrine
• Mixed Acting: Ephedrine, Metaraminol

Adrenergic Antagonists (Sympatholytic Agents)

• Alpha Adrenergic Blockers: Tolazoline, Phentolamine, Phenoxybenzamine, Prazosin
• Beta Adrenergic Blockers: Propranolol, Atenolol, Carvedilol

Cholinergic Drugs (Parasympathomimetics)

• Direct Acting: Acetylcholine, Carbachol, Pilocarpine
• Cholinesterase Inhibitors (Indirect Acting): Neostigmine, Edrophonium chloride, Tacrine hydrochloride, Echothiophate iodide

Cholinergic Blocking Agents (Anticholinergics)

• Natural: Atropine sulphate, Ipratropium bromide
• Synthetic: Tropicamide, Cyclopentolate hydrochloride, Clidinium bromide, Dicyclomine hydrochloride

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Chapter 6 – Detailed Notes (unit-wise)

This chapter is long, so we have broken it into 4 focused articles. Each part covers a specific section of the syllabus in complete detail with IUPAC names, uses, formulations, brand names, and exam tips.

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Unit 1 – Direct Acting Sympathomimetic Agents

Covers: Norepinephrine, Phenylephrine, Terbutaline, Naphazoline, Epinephrine, Dopamine, Salbutamol, Tetrahydrozoline

This is the largest group in the chapter and carries the most exam weight. You will learn how catecholamines differ from non-catecholamines, why some drugs need refrigeration while others do not, and the receptor selectivity behind each drug’s clinical use.

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Unit 2 – Indirect Acting, Mixed Acting Agents and Alpha Blockers

Covers: Hydroxyamphetamine, Pseudoephedrine, Ephedrine, Metaraminol, Tolazoline, Phentolamine, Phenoxybenzamine, Prazosin

This part explains the critical difference between direct and indirect mechanisms, why ephedrine can be taken orally while epinephrine cannot, and how alpha blockers differ from each other in selectivity and reversibility.

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Unit 3 – Beta Blockers and Direct Acting Cholinergic Drugs

Covers: Propranolol, Atenolol, Carvedilol, Acetylcholine, Carbachol, Pilocarpine

Here you will understand why propranolol is contraindicated in asthma, what makes carvedilol unique among beta blockers, and why so many cholinergic drugs end up as eye drops.

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Unit 4 – Cholinesterase Inhibitors and Anticholinergic Drugs

Covers: Neostigmine, Edrophonium, Tacrine, Echothiophate, Atropine, Ipratropium, Tropicamide, Cyclopentolate, Clidinium, Dicyclomine

The final part covers reversible vs irreversible enzyme inhibition, the Tensilon test for myasthenia gravis diagnosis, and the difference between natural and synthetic anticholinergics.

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Quick Reference: All Chapter 6 Drugs at a Glance

Drug	Class	IUPAC Name	Key Use	Brand Name
Norepinephrine	Direct sympathomimetic (α1, α2, β1)	4-[(1R)-2-amino-1-hydroxyethyl]benzene-1,2-diol	Septic shock vasopressor	Levophed
Phenylephrine	Direct sympathomimetic (α1)	(R)-3-[-1-hydroxy-2-(methylamino)ethyl]phenol	Nasal decongestant	Nostril
Epinephrine	Direct sympathomimetic (all α and β)	4-[(1R)-1-hydroxy-2-(methylamino)ethyl]benzene-1,2-diol	Anaphylaxis	EpiPen
Dopamine	Direct sympathomimetic (D1, β1, α1)	4-(2-aminoethyl)benzene-1,2-diol	Shock, heart failure	Intropin
Salbutamol	Direct sympathomimetic (β2)	(RS)-4-[2-(tert-Butylamino)-1-hydroxyethyl]-2-(hydroxymethyl)phenol	Asthma	Ventolin
Terbutaline	Direct sympathomimetic (β2)	(RS)-5-[2-(tert-Butylamino)-1-hydroxyethyl]benzene-1,3-diol	Asthma, preterm labor	Brethine
Naphazoline	Direct sympathomimetic (α1, α2)	2-(naphthalen-1-ylmethyl)-4,5-dihydro-1H-imidazole	Eye redness, nasal congestion	Naphcon-A
Tetrahydrozoline	Direct sympathomimetic (α)	(RS)-2-(1,2,3,4-tetrahydronaphthalen-1-yl)-4,5-dihydro-1H-imidazole	Eye redness	Visine
Hydroxyamphetamine	Indirect sympathomimetic	Hydroxyamphetamine hydrobromide	Mydriasis (eye exam)	Paremyd
Pseudoephedrine	Indirect sympathomimetic	(S,S)-2-methylamino-1-phenylpropan-1-ol	Nasal decongestant	Sudafed
Ephedrine	Mixed sympathomimetic	benzenemethanol α-[1-(methylamino)ethyl]-sulfate	Anaesthesia hypotension	Akovaz
Metaraminol	Mixed sympathomimetic (α dominant)	(1R,2S)-3-[-2-amino-1-hydroxy-propyl]phenol	Anaesthesia hypotension	Aramine
Tolazoline	Alpha blocker (non-selective)	2-Benzyl-4,5-dihydro-1H-imidazole	Pulmonary hypertension	Priscoline
Phentolamine	Alpha blocker (non-selective)	3-[(4,5-Dihydro-1H-imidazol-2-ylmethyl)(4-methylphenyl)amino]phenol	Pheochromocytoma	Regitine
Phenoxybenzamine	Alpha blocker (irreversible)	N-(2-chloroethyl)-N-(1-methyl-2-phenoxyethyl)benzylamine	Pheochromocytoma preop	Dibenzyline
Prazosin	Alpha-1 blocker (selective)	4-(4-Amino-6,7-dimethoxy-2-quinazolinyl)-1-piperazinylmethanone	Hypertension, BPH	Minipress
Propranolol	Beta blocker (non-selective)	1-(1-isopropylamino)-3-(1-naphthoxy)-2-propanol	Hypertension, migraine, arrhythmia	Inderal
Atenolol	Beta blocker (β1 selective)	[4-[2-hydroxy-3-isopropyl-aminopropoxy]-phenyl-acetamide]	Hypertension, angina	Tenormin
Carvedilol	Beta + alpha-1 blocker	(2RS)-1-(9H-carbazol-4-yloxy)-3-[[2-(2-methoxyphenoxy)ethyl]amino]propan-2-ol	Heart failure, hypertension	Coreg
Acetylcholine	Direct cholinergic	2-Acetoxy-N,N,N-trimethylethanaminium	Ophthalmic miosis	Miochol-E
Carbachol	Direct cholinergic (resistant to AChE)	2-[(Aminocarbonyl)oxy]-N,N,N-trimethylethanaminium chloride	Glaucoma, ophthalmic miosis	Miostat
Pilocarpine	Direct cholinergic (muscarinic agonist)	(3S,4R)-3-Ethyl-4-((1-methyl-1H-imidazol-5-yl)methyl)dihydrofuran-2(3H)-one	Glaucoma, dry mouth	Salagen
Neostigmine	ChEI (reversible, no BBB)	3-{[(Dimethylamino)carbonyl]oxy}-N,N,N-trimethylbenzenaminium	Myasthenia gravis, NMB reversal	Prostigmin
Edrophonium	ChEI (ultra-short)	N-ethyl-3-hydroxy-N,N-dimethylbenzenaminium chloride	Diagnosis of myasthenia gravis	Tensilon
Tacrine	ChEI (central, crosses BBB)	1,2,3,4-Tetrahydroacridin-9-amine hydrochloride	Alzheimer’s disease	Cognex
Echothiophate	ChEI (irreversible, organophosphate)	2-(Diethoxyphosphorylsulfanyl)ethyl-N,N,N-trimethylazanium iodide	Glaucoma	Phospholine Iodide
Atropine sulphate	Anticholinergic (natural)	Hyoscyamine Sulfate	Bradycardia, organophosphate poisoning	Isopto Atropine
Ipratropium bromide	Anticholinergic (quaternary)	[8-methyl-8-(1-methylethyl)-8-azoniabicyclo[3.2.1]oct-3-yl] 3-hydroxy-2-phenylpropanoate	COPD bronchodilator	Atrovent
Tropicamide	Synthetic anticholinergic	Benzeneacetamide, N-ethyl-α-(hydroxymethyl)-N-(4-pyridinylmethyl)-	Mydriasis for eye exam	Mydriacyl
Cyclopentolate	Synthetic anticholinergic	(RS)-2-(dimethylamino)ethyl (1-hydroxycyclopentyl)(phenyl)acetate	Cycloplegic refraction	Cyclogyl
Clidinium bromide	Synthetic anticholinergic (GI)	3-[(2-hydroxy-2,2-diphenylacetyl)oxy]-1-methyl-1-azabicyclo[2.2.2]octan-1-ium bromide	IBS, peptic ulcer	Librax
Dicyclomine HCl	Synthetic anticholinergic + antispasmodic	2-(diethylamino)ethyl 1-cyclohexylcyclohexanecarboxylate	IBS antispasmodic	Bentyl

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Most Asked Exam Questions from Chapter 6

These are the most frequently appearing questions from Chapter 6 in D.Pharm first year university examinations:

Short answer questions:

• Write a short note on beta adrenergic blockers
• Explain the mechanism of action of atropine
• What are sympathomimetic agents? Give classification with examples
• Write a short note on pilocarpine
• Explain the use of neostigmine in myasthenia gravis
• What is the IUPAC name and use of propranolol?
• Differentiate between direct and indirect acting sympathomimetics
• Write the IUPAC name and uses of salbutamol
• What are cholinesterase inhibitors? Give examples

Long answer questions:

• Classify adrenergic agonists with examples and explain the mechanism of any two drugs
• Describe the pharmacology of beta adrenergic blockers with mechanism, uses, side effects and contraindications
• Classify anticholinergic drugs. Explain the mechanism, uses, side effects and contraindications of atropine sulphate
• Write in detail about cholinergic drugs and cholinesterase inhibitors

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Key Concepts to Remember for Exams

Direct vs indirect sympathomimetics — Direct agents bind the receptor themselves. Indirect agents release stored norepinephrine. Indirect agents fail in patients with depleted norepinephrine stores.

Cardioselective vs non-selective beta blockers — Cardioselective agents (atenolol, metoprolol) preferentially block beta-1. Non-selective agents (propranolol) block both beta-1 and beta-2. Non-selective agents are contraindicated in asthma.

Reversible vs irreversible cholinesterase inhibition — Reversible agents (neostigmine, edrophonium) have limited duration. Irreversible agents (echothiophate, organophosphates) form permanent covalent bonds lasting days to weeks.

Quaternary vs tertiary amines — Quaternary ammonium compounds (neostigmine, ipratropium) carry a permanent positive charge and cannot cross the blood-brain barrier. Tertiary amines (atropine, physostigmine) cross the BBB and have CNS effects.

SLUDGE vs anti-SLUDGE — SLUDGE describes cholinergic toxicity (salivation, lacrimation, urination, defecation, GI distress, emesis). Anticholinergics produce the opposite — dry mouth, urinary retention, constipation, reduced secretions.

Alpha blockade before beta blockade in pheochromocytoma — Alpha blockade must always be established before beta blockade. Starting beta blockade first leaves alpha-mediated vasoconstriction unopposed, causing severe hypertensive crisis.

Tachyphylaxis with ephedrine — Repeated doses of ephedrine become less effective because each dose depletes the norepinephrine stores in nerve terminals that the drug relies on for its indirect action.

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Summary Mnemonics for Quick Revision

Adrenergic receptor effects: B1 = Heart (Beat — 1 heart); B2 = Lungs and Blood vessels (2 things — breathe and bleed); A1 = Vasoconstriction (Alpha squeeze); A2 = Presynaptic (Auto-inhibition)

Cholinergic toxicity — SLUDGE: Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis

Anticholinergic toxidrome: “Hot as a hare” (hyperthermia), “Dry as a bone” (anhydrosis), “Red as a beet” (flushing), “Blind as a bat” (mydriasis), “Mad as a hatter” (delirium), “Full as a flask” (urinary retention)

Drugs used in myasthenia gravis (ChEIs): NET — Neostigmine, Edrophonium (diagnosis), Tacrine (historical)

Beta blocker order — alphabetical = selectivity: Atenolol = Alpha-1 spared (beta-1 selective); Propranolol = Pan-beta blocker (non-selective); Carvedilol = Combined alpha + beta blocker

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Frequently Asked Questions — ANS