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Phentolamine Information

Phentolamine (Regitine) is a reversible[1] nonselective alpha-adrenergic antagonist. [2]

Contents

Mechanism

Its primary action is vasodilation due to α1 blockade.[3]

It also can lead to reflex tachycardia because of hypotension and α2 inhibition, which increases sympathetic tone.[4]

Uses

The primary application for phentolamine is for the control of hypertensive emergencies, most notably due to pheochromocytoma.[5]

It also has usefulness in the treatment of cocaine induced hypertension, where one would generally avoid beta blockers and where calcium channel blockers are not effective. Beta-blockers (i.e. metoprolol) or combined alpha and beta adrenergic blocking agents (i.e. labetalol) should be avoided in patients with a history of cocaine abuse. They can cause an unopposed alpha-adrenergic mediated coronary vasoconstriction, causing the worsening of myocardial ischemia and hypertension.

[6][7] In this context it is probably most safely given by infusion since bolus doses have a propensity towards causing precipitous falls in blood pressure.

When given by injection it causes blood vessels to expand, thereby increasing blood flow. When injected into the penis (intracavernosal), it increases blood flow to the penis, which results in an erection.[8]

It may be stored in crash carts to counteract severe peripheral vasoconstriction secondary to extravasation of peripherally placed vasopressor infusions, typically of norepinephrine. Epinephrine infusions are less vasoconstrictive than norepinephrine as they primarily stimulate beta receptor more than alpha receptors, but the effect remains dose dependent.

Phentolamine also has diagnostic and therapeutic roles in complex regional pain syndrome (reflex sympathetic dystrophy).[9]

Phentolamine has recently been introduced in the dental field as a local anesthetic reversal agent. Distributed by Novalar, OraVerse is a Phentolamine Mesylate injection designed to reverse the local vasoconstrictor properties used in many local anesthetics to prolong anesthesia.[10] OraVerse has been shown to accelerate the reversal of the lingering soft-tissue numbness associated with the widely used anesthetic-vasoconstrictor combinations.[11]

Chemistry

Phentolamine, 2-[[N-(3′-hydroxyphenyl)-para-toluidion]methyl]-2-imidazoline, is synthesized by alkylation of 3-(4-methylanilino)phenol using 2-chloromethylimidazoline.

References

  1. ^ Jewell, John R.; Longworth, David L.; Stoller, James K.; Casey, David (2003). The Cleveland Clinic internal medicine case reviews. Hagerstown, MD: Lippincott Williams & Wilkins. p. 32. ISBN 0-7817-4266-8.
  2. ^ MeSH Phentolamine
  3. ^ Brock G. Oral phentolamine (Vasomax). Drugs Today (Barcelona). 2000 Feb-Mar;36(2-3):121-4.
  4. ^ Shen, Howard (2008). Illustrated Pharmacology Memory Cards: PharMnemonics. Minireview. p. 14. ISBN 1-59541-101-1.
  5. ^ Tuncel M, Ram VC. Hypertensive emergencies. Etiology and management. American Journal of Cardiovascular Drugs. 2003;3(1):21-31.
  6. ^ Hollander JE, Henry TD. Evaluation and management of the patient who has cocaine-associated chest pain. Cardiology Clinics. 2006 Feb;24(1):103-14.
  7. ^ Chan GM, Sharma R, Price D, Hoffman RS, Nelson LS. Phentolamine Therapy for Cocaine-Association Acute Coronary Syndrome (CAACS). Journal of Medical Toxicology. 2006 Sep;2(3):108-11.
  8. ^ Bella AJ, Brock GB. Intracavernous pharmacotherapy for erectile dysfunction. Endocrine. 2004 Mar-Apr;23(2-3):149-55.
  9. ^ Rowbotham MC. Pharmacologic management of complex regional pain syndrome. Clinical Journal of Pain. 2006 Jun;22(5):425-9.
  10. ^ http://www.novalar.com/oraverse-dental-specialty-pharmaceutical
  11. ^ Malamed S. What's new in local anaesthesia? Society For The Advancement Of Anaesthesia In Dentistry Digest. 2009 Jan;25:4-14.
· · Sympatholytic (and closely related) antihypertensives (C02)
Sympatholytics (antagonize α-adrenergic vasoconstriction)
Central
α2 agonist Clonidine • Guanfacine • Methyldopa #
Adrenergic release inhibitors Bethanidine • Bretylium • Debrisoquine • Guanadrel • Guanazodine • Guanethidine • Guanoclor • Guanoxan • Guanazodine • Guanoxabenz • Guanoxan
Imidazoline receptor agonist Moxonidine • Rilmenidine
Ganglion-blocking/nicotinic antagonist Mecamylamine • Pentolinium • Trimethaphan
Peripheral
Indirect
MAOI Pargyline
Adrenergic uptake inhibitor Rescinnamine • Reserpine
Tyrosine hydroxylase inhibitor Metirosine
Direct
α1 blockers Prazosin • Indoramin • Trimazosin • Doxazosin • Urapidil
Non-selective α blocker Phentolamine
Other antagonists
Serotonin antagonist Ketanserin
Endothelin antagonist (for PH) dual (Bosentan) • selective (Ambrisentan, Sitaxentan)
#WHO-EM. ‡Withdrawn from market. Clinical trials: †Phase III. §Never to phase III

: VAS

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, drug(+//////)
· · Peripheral vasodilators (C04)
2-amino-1-phenylethanol derivatives Isoxsuprine • Buphenine • Bamethan
Imidazoline derivatives/ Alpha blockers Phentolamine • Tolazoline • Phenoxybenzamine
Niacin and derivatives Niacin • Nicotinyl alcohol • Inositol nicotinate • Ciclonicate
Purine derivatives Pentifylline • Xantinol nicotinate • Pentoxifylline • Etofylline nicotinate
Ergot alkaloids Ergoloid • Nicergoline • Dihydroergocristine
Other peripheral vasodilators Cyclandelate • Phenoxybenzamine • Vincamine • Moxisylyte • Bencyclane • Vinburnine • Sulcotidil • Buflomedil • Naftidrofuryl • Butalamine • Visnadine • Cetiedil • Cinepazide • Ifenprodil • Azapetine • Fasudil

: VAS

(a:////,v:////)////

////, /,

, drug(+//////)
· · Drugs for erectile dysfunction (G04BE) and premature ejaculation
For erectile dysfunction
Prostaglandins (E) Alprostadil
PDE5 inhibitors Avanafil • Sildenafil • Tadalafil • Udenafil • Vardenafil
Alpha blockers Moxisylyte • Phentolamine • Yohimbine
Dopamine D4 receptor agonists ABT-670 • ABT-724
Others Apomorphine • Papaverine
SSRI for PE Dapoxetine

: ♂ MRS

//

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, drug (//)
· · Adrenergics
Receptor ligands
α1 Agonists: 5-FNE • 6-FNE • Amidephrine • Anisodamine • Anisodine • Cirazoline • Dipivefrine • Dopamine • Ephedrine • Epinephrine (Adrenaline) • Etilefrine • Ethylnorepinephrine • Indanidine • Levonordefrin • Metaraminol • Methoxamine • Methyldopa • Midodrine • Naphazoline • Norepinephrine (Noradrenaline) • Octopamine • Oxymetazoline • Phenylephrine • Phenylpropanolamine • Pseudoephedrine • Synephrine • Tetrahydrozoline Antagonists: Abanoquil • Adimolol • Ajmalicine • Alfuzosin • Amosulalol • Arotinolol • Atiprosin • Benoxathian • Buflomedil • Bunazosin • Carvedilol • CI-926 • Corynanthine • Dapiprazole • DL-017 • Domesticine • Doxazosin • Eugenodilol • Fenspiride • GYKI-12,743 • GYKI-16,084 • Indoramin • Ketanserin • L-765,314 • Labetalol • Mephendioxan • Metazosin • Monatepil • Moxisylyte (Thymoxamine) • Naftopidil • Nantenine • Neldazosin • Nicergoline • Niguldipine • Pelanserin • Phendioxan • Phenoxybenzamine • Phentolamine • Piperoxan • Prazosin • Quinazosin • Ritanserin • RS-97,078 • SGB-1,534 • Silodosin • SL-89.0591 • Spiperone • Talipexole • Tamsulosin • Terazosin • Tibalosin • Tiodazosin • Tipentosin • Tolazoline • Trimazosin • Upidosin • Urapidil • Zolertine * Note that many TCAs, TeCAs, antipsychotics, ergolines, and some piperazines like buspirone, trazodone, nefazodone, etoperidone, and mepiprazole all antagonize α1-adrenergic receptors as well, which contributes to their side effects such as orthostatic hypotension.
α2 Agonists: (R)-3-Nitrobiphenyline • 4-NEMD • 6-FNE • Amitraz • Apraclonidine • Brimonidine • Cannabivarin • Clonidine • Detomidine • Dexmedetomidine • Dihydroergotamine • Dipivefrine • Dopamine • Ephedrine • Ergotamine • Epinephrine (Adrenaline) • Esproquin • Etilefrine • Ethylnorepinephrine • Guanabenz • Guanfacine • Guanoxabenz • Levonordefrin • Lofexidine • Medetomidine • Methyldopa • Mivazerol • Naphazoline • Norepinephrine (Noradrenaline) • Phenylpropanolamine • Piperoxan • Pseudoephedrine • Rilmenidine • Romifidine • Talipexole • Tetrahydrozoline • Tizanidine • Tolonidine • Urapidil • Xylazine • Xylometazoline Antagonists: 1-PP • Adimolol • Aptazapine • Atipamezole • BRL-44408 • Buflomedil • Cirazoline • Efaroxan • Esmirtazapine • Fenmetozole • Fluparoxan • GYKI-12,743 • GYKI-16,084 • Idazoxan • Mianserin • Mirtazapine • MK-912 • NAN-190 • Olanzapine • Phentolamine • Phenoxybenzamine • Piperoxan • Piribedil • Rauwolscine • Rotigotine • SB-269,970 • Setiptiline • Spiroxatrine • Sunepitron • Tolazoline • Yohimbine * Note that many atypical antipsychotics and azapirones like buspirone and gepirone (via metabolite 1-PP) antagonize α2-adrenergic receptors as well.
β Agonists: 2-FNE • 5-FNE • Amibegron • Arbutamine • Arformoterol • Arotinolol • BAAM • Bambuterol • Befunolol • Bitolterol • Broxaterol • Buphenine • Carbuterol • Cimaterol • Clenbuterol • Denopamine • Deterenol • Dipivefrine • Dobutamine • Dopamine • Dopexamine • Ephedrine • Epinephrine (Adrenaline) • Etafedrine • Etilefrine • Ethylnorepinephrine • Fenoterol • Formoterol • Hexoprenaline • Higenamine • Indacaterol • Isoetarine • Isoprenaline (Isoproterenol) • Isoxsuprine • Labetalol • Levonordefrin • Levosalbutamol • Mabuterol • Methoxyphenamine • Methyldopa • N-Isopropyloctopamine • Norepinephrine (Noradrenaline) • Orciprenaline • Oxyfedrine • Phenylpropanolamine • Pirbuterol • Prenalterol • Ractopamine • Procaterol • Pseudoephedrine • Reproterol • Rimiterol • Ritodrine • Salbutamol (Albuterol) • Salmeterol • Solabegron • Terbutaline • Tretoquinol • Tulobuterol • Xamoterol • Zilpaterol • Zinterol Antagonists: Acebutolol • Adaprolol • Adimolol • Afurolol • Alprenolol • Alprenoxime • Amosulalol • Ancarolol • Arnolol • Arotinolol • Atenolol • Befunolol • Betaxolol • Bevantolol • Bisoprolol • Bopindolol • Bormetolol • Bornaprolol • Brefonalol • Bucindolol • Bucumolol • Bufetolol • Buftiralol • Bufuralol • Bunitrolol • Bunolol • Bupranolol • Burocrolol • Butaxamine • Butidrine • Butofilolol • Capsinolol • Carazolol • Carpindolol • Carteolol • Carvedilol • Celiprolol • Cetamolol • Cicloprolol • Cinamolol • Cloranolol • Cyanopindolol • Dalbraminol • Dexpropranolol • Diacetolol • Dichloroisoprenaline • Dihydroalprenolol • Dilevalol • Diprafenone • Draquinolol • Dropranolol • Ecastolol • Epanolol • Ericolol • Ersentilide • Esatenolol • Esmolol • Esprolol • Eugenodilol • Exaprolol • Falintolol • Flestolol • Flusoxolol • Hydroxycarteolol • Hydroxytertatolol • ICI-118,551 • Idropranolol • Indenolol • Indopanolol • Iodocyanopindolol • Iprocrolol • Isoxaprolol • Isamoltane • Labetalol • Landiolol • Levobetaxolol • Levobunolol • Levocicloprolol • Levomoprolol • Medroxalol • Mepindolol • Metalol • Metipranolol • Metoprolol • Moprolol • Nadolol • Nadoxolol • Nafetolol • Nebivolol • Neraminol • Nifenalol • Nipradilol • Oberadilol • Oxprenolol • Pacrinolol • Pafenolol • Pamatolol • Pargolol • Parodilol • Penbutolol • Penirolol • PhQA-33 • Pindolol • Pirepolol • Practolol • Primidolol • Procinolol • Pronethalol • Propafenone • Propranolol • Ridazolol • Ronactolol • Soquinolol • Sotalol • Spirendolol • SR 59230A • Sulfinalol • TA-2005 • Talinolol • Tazolol • Teoprolol • Tertatolol • Terthianolol • Tienoxolol • Tilisolol • Timolol • Tiprenolol • Tolamolol • Toliprolol • Tribendilol • Trigevolol • Xibenolol • Xipranolol
Reuptake inhibitors
NET Selective norepinephrine reuptake inhibitors: Amedalin • Atomoxetine (Tomoxetine) • Ciclazindol • Daledalin • Esreboxetine • Lortalamine • Mazindol • Nisoxetine • Reboxetine • Talopram • Talsupram • Tandamine • Viloxazine; Norepinephrine-dopamine reuptake inhibitors: Amineptine • Bupropion (Amfebutamone) • Fencamine • Fencamfamine • Lefetamine • Levophacetoperane • LR-5182 • Manifaxine • Methylphenidate • Nomifensine • O-2172 • Radafaxine; Serotonin-norepinephrine reuptake inhibitors: Bicifadine • Desvenlafaxine • Duloxetine • Eclanamine • Levomilnacipran • Milnacipran • Sibutramine • Venlafaxine; Serotonin-norepinephrine-dopamine reuptake inhibitors: Brasofensine • Diclofensine • DOV-102,677 • DOV-21,947 • DOV-216,303 • JNJ-7925476 • JZ-IV-10 • Methylnaphthidate • Naphyrone • NS-2359 • PRC200-SS • SEP-225,289 • SEP-227,162 • Tesofensine; Tricyclic antidepressants: Amitriptyline • Butriptyline • Cianopramine • Clomipramine • Desipramine • Dosulepin • Doxepin • Imipramine • Lofepramine • melitracen • Nortriptyline • Protriptyline • Trimipramine; Tetracyclic antidepressants: Amoxapine • Maprotiline • Mianserin • Oxaprotiline • Setiptiline; Others: Cocaine • CP-39,332 • EXP-561 • Fezolamine • Nefazodone • Nefopam • Pridefrine • Tapentadol • Tramadol • Ziprasidone
VMAT Ibogaine • Reserpine • Tetrabenazine
Releasing agents
Morpholines: Fenbutrazate • Morazone • Phendimetrazine • Phenmetrazine; Oxazolines: 4-Methylaminorex • Aminorex • Clominorex • Cyclazodone • Fenozolone • Fluminorex • Pemoline • Thozalinone; Phenethylamines (also amphetamines, cathinones, phentermines, etc): 2-OH-PEA • 4-CAB • 4-FA • 4-FMA • 4-MA • 4-MMA • Alfetamine • Amfecloral • Amfepentorex • Amfepramone • Amphetamine (Dextroamphetamine, Levoamphetamine) • Amphetaminil • β-Me-PEA • BDB • Benzphetamine • BOH • Buphedrone • Butylone • Cathine • Cathinone • Clobenzorex • Clortermine • D-Deprenyl • Dimethylamphetamine • Dimethylcathinone (Dimethylpropion, metamfepramone) • DMA • DMMA • EBDB • Ephedrine • Ethcathinone • Ethylamphetamine • Ethylone • Famprofazone • Fenethylline • Fenproporex • Flephedrone • Fludorex • Furfenorex • Hordenine • IAP • IMP • L-Deprenyl (Selegiline) • Lisdexamfetamine • Lophophine • MBDB • MDA (Tenamfetamine) • MDEA • MDMA • MDMPEA • MDOH • MDPEA • Mefenorex • Mephedrone • Mephentermine • Methamphetamine (Dextromethamphetamine, Levomethamphetamine) • Methcathinone • Methedrone • Methylone • NAP • Ortetamine • Paredrine • pBA • pCA • Pentorex (Phenpentermine) • Phenethylamine • Pholedrine • Phenpromethamine • Phentermine • Phenylpropanolamine • pIA • Prenylamine • Propylamphetamine • Pseudoephedrine • Tiflorex • Tyramine • Xylopropamine • Zylofuramine; Piperazines: 2C-B-BZP • BZP • MBZP • mCPP • MDBZP • MeOPP • pFPP; Others: 2-Amino-1,2-dihydronaphthalene • 2-Aminoindane • 2-Aminotetralin • 2-Benzylpiperidine • 4-Benzylpiperidine • 5-IAI • Clofenciclan • Cyclopentamine • Cypenamine • Cyprodenate • Feprosidnine • Gilutensin • Heptaminol • Hexacyclonate • Indanorex • Isometheptene • Methylhexanamine • Octodrine • Phthalimidopropiophenone • Propylhexedrine (Levopropylhexedrine) • Tuaminoheptane
Enzyme inhibitors
Anabolism
PAH 3,4-Dihydroxystyrene
TH 3-Iodotyrosine • Aquayamycin • Bulbocapnine • Metirosine • Oudenone
AAAD Benserazide • Carbidopa • Genistein • Methyldopa
DBH Bupicomide • Disulfiram • Dopastin • Fusaric acid • Nepicastat • Phenopicolinic acid • Tropolone
PNMT CGS-19281A • SKF-64139 • SKF-7698
Catabolism
MAO Nonselective: Benmoxin • Caroxazone • Echinopsidine • Furazolidone • Hydralazine • Indantadol • Iproclozide • Iproniazid • Isocarboxazid • Isoniazid • Linezolid • Mebanazine • Metfendrazine • Nialamide • Octamoxin • Paraxazone • Phenelzine • Pheniprazine • Phenoxypropazine • Pivalylbenzhydrazine • Procarbazine • Safrazine • Tranylcypromine; MAO-A selective: Amiflamine • Bazinaprine • Befloxatone • Befol • Brofaromine • Cimoxatone • Clorgiline • Esuprone • Harmala alkaloids (Harmine, Harmaline, Tetrahydroharmine, Harman, Norharman, etc) • Methylene Blue • Metralindole • Minaprine • Moclobemide • Pirlindole • Sercloremine • Tetrindole • Toloxatone • Tyrima; MAO-B selective: D-Deprenyl • Selegiline (L-Deprenyl) • Ladostigil • Lazabemide • Milacemide • Mofegiline • Pargyline • Rasagiline * Note that MAO-B inhibitors also influence norepinephrine/epinephrine levels since they inhibit the breakdown of their precursor dopamine.
COMT Entacapone • Tolcapone
Others
Precursors L-Phenylalanine → L-Tyrosine → L-DOPA (Levodopa) → Dopamine • L-DOPS (Droxidopa)
Cofactors Ferrous Iron (Fe2+) • S-Adenosyl-L-Methionine • Vitamin B3 (Niacin, Nicotinamide → NADPH) • Vitamin B6 (Pyridoxine, Pyridoxamine, Pyridoxal → Pyridoxal Phosphate) • Vitamin B9 (Folic acid → Tetrahydrofolic acid) • Vitamin C (Ascorbic acid) • Zinc (Zn2+)
Others Activity enhancers: BPAP • PPAP; Release blockers: Bethanidine • Bretylium • Guanadrel • Guanazodine • Guanclofine • Guanethidine • Guanoxan; Toxins: Oxidopamine (6-Hydroxydopamine)

Categories: Antihypertensive agents | Vasodilators | Imidazolines | Alpha blockers | Phenols | Anilines

 

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