This browser is too old to run Achievable.

Update it, or open this page in a current version of Chrome, Safari, Firefox or Edge. On an iPhone or iPad, update iOS: every browser there runs on the version of Safari that comes with it.

Achievable logoAchievable logo
USMLE/1
Sign in
Sign up
Purchase
Textbook
Support
How it works
Resources
Exam catalog
Mountain with a flag at the peak
Textbook
Introduction
1. Anatomy
2. Microbiology
3. Physiology
4. Pathology
5. Pharmacology
5.1 Pharmacokinetics
5.2 Pharmacodynamics
5.3 Receptors, agonists and antagonists
5.4 Types of drug receptors
5.5 Anti-neoplastic drugs
5.6 Adverse effects of chemotherapeutic drugs
5.7 Newer chemotherapeutic drugs
5.8 Important drugs of the cardiovascular system
5.9 Antimicrobials
5.10 Drugs acting on the renal system
5.11 Drugs acting on the respiratory system
5.12 Drugs acting on the gastrointestinal system
5.13 Antidiabetics and insulin
5.14 Miscellaneous
5.15 Additional information
6. Immunology
7. Biochemistry
8. Cell and molecular biology
9. Biostatistics and epidemiology
10. Genetics
11. Behavioral science
Wrapping up
Achievable logoAchievable logo
5.3 Receptors, agonists and antagonists
Achievable USMLE/1
5. Pharmacology

Receptors, agonists and antagonists

3 min read
Font
Discuss
Share
Feedback

Receptors and drugs acting as agonists and antagonists

Receptor Agonist Antagonist
Alpha 1 (dilator pupillae, vascular smooth muscle) Dopamine; Phenylephrine Prazosin; Doxazosin
Alpha 2 (CNS, presynaptic nerve terminals) Clonidine Yohimbine
Beta 1 (heart, CNS) Dopamine; Dobutamine Atenolol; Metoprolol; Propranolol
Beta 2 (islet cells of pancreas, smooth muscle in bronchioles, blood vessels and uterus) Salbutamol; Terbutaline
Beta 3 Mirabegron
Alpha and beta Epinephrine; Norepinephrine (alpha > beta; causes reflex bradycardia) Labetalol
Alpha Phentolamine (reversible); Phenoxybenzamine (irreversible)
Beta 1 and beta 2 Dopamine; Isoprenaline Propranolol; Oxprenolol
Angiotensin or AT 1 and AT 2 Angiotensin Candesartan (most potent blocker of AT1 receptor); Losartan; Telmisartan; Irbesartan; Valsartan (all selective for AT1 over AT2)
Muscarinic Acetylcholine; Carbachol; Bethanechol Atropine and analogues; Homatropine; Pirenzepine (M1); Trihexyphenidyl; Tricyclic antidepressants; Quinidine; Disopyramide
Nicotinic Acetylcholine; Carbachol Ganglion blockers; Neuromuscular blockers; Aminoglycoside antibiotics; Quinidine
Dopamine Apomorphine; Bromocriptine; Dopamine Butyrophenones, haloperidol; Domperidone (D2); Metoclopramide; Phenothiazines, chlorpromazine
GABA -A GABA; Benzodiazepines (positive allosteric modulators, not direct agonists) Bicuculline
GABA -B GABA; Baclofen
Histamine H1 Histamine Antihistamines like cetirizine, promethazine
Histamine H2 Histamine Cimetidine; Ranitidine; Famotidine
5 hydroxytryptamine or 5 HT 5HT; Sumatriptan (5HT 1B/1D) Methysergide; Ondansetron (5HT 3)
Leukotriene or LT Leukotrienes Montelukast; Zafirlukast
Opioid receptors (μ, δ, and κ) Morphine; Endorphins; Enkephalins; Pentazocine (κ; partial agonist at μ); Buprenorphine (μ) (partial agonist); Fentanyl, alfentanil, remifentanil; Oxycodone; Methadone; Codeine; Nalorphine (κ) Naltrexone (μ, δ, and κ); Methylnaltrexone (μ; peripherally acting); Nalorphine (μ); Naloxone (μ, δ, and κ; highest affinity at μ); Buprenorphine (κ)
Vasopressin V1 and V2 Vasopressin (ADH) Conivaptan (V1 and V2); Nelivaptan (V1b); Tolvaptan (V2)

Beta blockers and receptor selectivity

  • Beta 1 selective are acebutolol, atenolol, metoprolol, esmolol
  • Nonselective (beta 1=beta 2) are propranolol, timolol, nadolol
  • Nonselective (both alpha and beta) = labetalol, carvedilol

Alpha Receptors

  • Alpha 1 agonists: dopamine, phenylephrine; antagonists: prazosin, doxazosin
  • Alpha 2 agonist: clonidine; antagonist: yohimbine
  • Nonselective alpha antagonists: phentolamine (reversible), phenoxybenzamine (irreversible)

Beta Receptors

  • Beta 1 agonists: dopamine, dobutamine; antagonists: atenolol, metoprolol, propranolol
  • Beta 2 agonists: salbutamol, terbutaline
  • Beta 3 agonist: mirabegron
  • Beta 1 and 2 agonists: dopamine, isoprenaline; antagonists: propranolol, oxprenolol

Combined Alpha and Beta Receptors

  • Agonists: epinephrine, norepinephrine (alpha > beta, causes reflex bradycardia)
  • Antagonist: labetalol

Angiotensin Receptors (AT1, AT2)

  • Agonist: angiotensin
  • Antagonists, all selective for AT1 over AT2: candesartan (most potent), losartan, telmisartan, irbesartan, valsartan

Muscarinic and Nicotinic Receptors

  • Muscarinic agonists: acetylcholine, carbachol, bethanechol; antagonists: atropine, homatropine, pirenzepine (M1), trihexyphenidyl, tricyclic antidepressants, quinidine, disopyramide
  • Nicotinic agonists: acetylcholine, carbachol; antagonists: ganglion blockers, neuromuscular blockers, aminoglycosides, quinidine

Dopamine Receptors

  • Agonists: apomorphine, bromocriptine, dopamine
  • Antagonists: butyrophenones, haloperidol, domperidone (D2), metoclopramide, phenothiazines, chlorpromazine

GABA Receptors

  • GABA-A agonist: GABA; benzodiazepines are positive allosteric modulators; antagonist: bicuculline
  • GABA-B agonists: GABA, baclofen

Histamine Receptors

  • H1 agonist: histamine; antagonists: cetirizine, promethazine
  • H2 agonist: histamine; antagonists: cimetidine, ranitidine, famotidine

Serotonin (5 HT) Receptors

  • Agonists: 5HT, sumatriptan (5HT 1B/1D)
  • Antagonists: methysergide, ondansetron (5HT 3)

Leukotriene Receptors

  • Agonist: leukotrienes
  • Antagonists: montelukast, zafirlukast

Opioid Receptors (μ, δ, κ)

  • Agonists: morphine, endorphins, enkephalins, pentazocine (κ; partial at μ), buprenorphine (μ, partial), fentanyl, oxycodone, methadone, codeine, nalorphine (κ)
  • Antagonists: naltrexone (μ, δ, κ), methylnaltrexone (μ, peripherally acting), nalorphine (μ), naloxone (μ, δ, κ), buprenorphine (κ)

Vasopressin Receptors (V1, V2)

  • Agonist: vasopressin (ADH)
  • Antagonists: conivaptan (V1, V2), nelivaptan (V1b), tolvaptan (V2)

Beta Blockers and Receptor Selectivity

  • Beta 1 selective: acebutolol, atenolol, metoprolol, esmolol
  • Nonselective (beta 1 = beta 2): propranolol, timolol, nadolol
  • Nonselective (alpha and beta): labetalol, carvedilol
Previous
Next  | 5.4 Types of drug receptors
All rights reserved ©2016 - 2026 Achievable, Inc.

Receptors, agonists and antagonists

Receptors and drugs acting as agonists and antagonists

Receptor Agonist Antagonist
Alpha 1 (dilator pupillae, vascular smooth muscle) Dopamine; Phenylephrine Prazosin; Doxazosin
Alpha 2 (CNS, presynaptic nerve terminals) Clonidine Yohimbine
Beta 1 (heart, CNS) Dopamine; Dobutamine Atenolol; Metoprolol; Propranolol
Beta 2 (islet cells of pancreas, smooth muscle in bronchioles, blood vessels and uterus) Salbutamol; Terbutaline
Beta 3 Mirabegron
Alpha and beta Epinephrine; Norepinephrine (alpha > beta; causes reflex bradycardia) Labetalol
Alpha Phentolamine (reversible); Phenoxybenzamine (irreversible)
Beta 1 and beta 2 Dopamine; Isoprenaline Propranolol; Oxprenolol
Angiotensin or AT 1 and AT 2 Angiotensin Candesartan (most potent blocker of AT1 receptor); Losartan; Telmisartan; Irbesartan; Valsartan (all selective for AT1 over AT2)
Muscarinic Acetylcholine; Carbachol; Bethanechol Atropine and analogues; Homatropine; Pirenzepine (M1); Trihexyphenidyl; Tricyclic antidepressants; Quinidine; Disopyramide
Nicotinic Acetylcholine; Carbachol Ganglion blockers; Neuromuscular blockers; Aminoglycoside antibiotics; Quinidine
Dopamine Apomorphine; Bromocriptine; Dopamine Butyrophenones, haloperidol; Domperidone (D2); Metoclopramide; Phenothiazines, chlorpromazine
GABA -A GABA; Benzodiazepines (positive allosteric modulators, not direct agonists) Bicuculline
GABA -B GABA; Baclofen
Histamine H1 Histamine Antihistamines like cetirizine, promethazine
Histamine H2 Histamine Cimetidine; Ranitidine; Famotidine
5 hydroxytryptamine or 5 HT 5HT; Sumatriptan (5HT 1B/1D) Methysergide; Ondansetron (5HT 3)
Leukotriene or LT Leukotrienes Montelukast; Zafirlukast
Opioid receptors (μ, δ, and κ) Morphine; Endorphins; Enkephalins; Pentazocine (κ; partial agonist at μ); Buprenorphine (μ) (partial agonist); Fentanyl, alfentanil, remifentanil; Oxycodone; Methadone; Codeine; Nalorphine (κ) Naltrexone (μ, δ, and κ); Methylnaltrexone (μ; peripherally acting); Nalorphine (μ); Naloxone (μ, δ, and κ; highest affinity at μ); Buprenorphine (κ)
Vasopressin V1 and V2 Vasopressin (ADH) Conivaptan (V1 and V2); Nelivaptan (V1b); Tolvaptan (V2)

Beta blockers and receptor selectivity

  • Beta 1 selective are acebutolol, atenolol, metoprolol, esmolol
  • Nonselective (beta 1=beta 2) are propranolol, timolol, nadolol
  • Nonselective (both alpha and beta) = labetalol, carvedilol
Key points

Alpha Receptors

  • Alpha 1 agonists: dopamine, phenylephrine; antagonists: prazosin, doxazosin
  • Alpha 2 agonist: clonidine; antagonist: yohimbine
  • Nonselective alpha antagonists: phentolamine (reversible), phenoxybenzamine (irreversible)

Beta Receptors

  • Beta 1 agonists: dopamine, dobutamine; antagonists: atenolol, metoprolol, propranolol
  • Beta 2 agonists: salbutamol, terbutaline
  • Beta 3 agonist: mirabegron
  • Beta 1 and 2 agonists: dopamine, isoprenaline; antagonists: propranolol, oxprenolol

Combined Alpha and Beta Receptors

  • Agonists: epinephrine, norepinephrine (alpha > beta, causes reflex bradycardia)
  • Antagonist: labetalol

Angiotensin Receptors (AT1, AT2)

  • Agonist: angiotensin
  • Antagonists, all selective for AT1 over AT2: candesartan (most potent), losartan, telmisartan, irbesartan, valsartan

Muscarinic and Nicotinic Receptors

  • Muscarinic agonists: acetylcholine, carbachol, bethanechol; antagonists: atropine, homatropine, pirenzepine (M1), trihexyphenidyl, tricyclic antidepressants, quinidine, disopyramide
  • Nicotinic agonists: acetylcholine, carbachol; antagonists: ganglion blockers, neuromuscular blockers, aminoglycosides, quinidine

Dopamine Receptors

  • Agonists: apomorphine, bromocriptine, dopamine
  • Antagonists: butyrophenones, haloperidol, domperidone (D2), metoclopramide, phenothiazines, chlorpromazine

GABA Receptors

  • GABA-A agonist: GABA; benzodiazepines are positive allosteric modulators; antagonist: bicuculline
  • GABA-B agonists: GABA, baclofen

Histamine Receptors

  • H1 agonist: histamine; antagonists: cetirizine, promethazine
  • H2 agonist: histamine; antagonists: cimetidine, ranitidine, famotidine

Serotonin (5 HT) Receptors

  • Agonists: 5HT, sumatriptan (5HT 1B/1D)
  • Antagonists: methysergide, ondansetron (5HT 3)

Leukotriene Receptors

  • Agonist: leukotrienes
  • Antagonists: montelukast, zafirlukast

Opioid Receptors (μ, δ, κ)

  • Agonists: morphine, endorphins, enkephalins, pentazocine (κ; partial at μ), buprenorphine (μ, partial), fentanyl, oxycodone, methadone, codeine, nalorphine (κ)
  • Antagonists: naltrexone (μ, δ, κ), methylnaltrexone (μ, peripherally acting), nalorphine (μ), naloxone (μ, δ, κ), buprenorphine (κ)

Vasopressin Receptors (V1, V2)

  • Agonist: vasopressin (ADH)
  • Antagonists: conivaptan (V1, V2), nelivaptan (V1b), tolvaptan (V2)

Beta Blockers and Receptor Selectivity

  • Beta 1 selective: acebutolol, atenolol, metoprolol, esmolol
  • Nonselective (beta 1 = beta 2): propranolol, timolol, nadolol
  • Nonselective (alpha and beta): labetalol, carvedilol

More from Pharmacology

  • Pharmacokinetics
  • Pharmacodynamics
  • Types of drug receptors
  • Anti-neoplastic drugs
  • Adverse effects of chemotherapeutic drugs