1-1 section i · 1-6 atropine autonomic, autacoid, and neuromuscular drugs therapeutic...

1-11-1 Section I Autonomic, Autacoid, and Neuromuscular Drugs

Atropine Epoprostenol Phenylephrine Pyridostigmine Tamsulosin

Bosentan Metoprolol Pilocarpine Rocuronium Terazosin

Dobutamine Metyrosine Pralidoxime Sildenafil

Edrophonium Phenoxybenzamine Propranolol Solifenacin

Epinephrine Phentolamine Pseudoephedrine Succinylcholine

Cholinergic and adrenergic neurotransmission and sites of drug action. See figure on back of card. In skeletal muscle, acetylcholine (Ach) activates nicotinic (N) receptors causing muscle contraction. Neuromuscular blockers (rocuronium) compete with Ach for N receptors and cause muscle relaxation. In smooth muscle and glands, Ach and pilocarpine activate muscarinic (M) receptors, causing muscle contraction and gland secretion. M receptor antagonists (atropine) cause muscle relaxation and inhibit secretions. Norepinephrine (NE) and epinephrine (E) activate α and β adrenoceptors and cause smooth muscle contraction or relaxation, respectively. Activation of cardiac β-receptors leads to increased heart rate, contractility, and conduction velocity. α-Blockers (terazosin) relax vascular and bladder smooth muscle, whereas β-blockers (propranolol) slow heart rate and decrease cardiac output and blood pressure. (α = alpha, β = beta.)

1-2 Autonomic, Autacoid, and Neuromuscular Drugs

Cholinergic and adrenergic neurotransmission and sites of drug action. See back of card for description.

M2

M3

β1

Smoothmuscle

α1

β2

AchAch N

Parasympathetic nerves

Sympathetic nerves

Ach N

Ach

Ach

E and NEin the blood

Skeletalmuscle

Exocrine glands

Heart

Adrenalmedulla

Somatic nerves

NE

N

N

M3


Sites of action of drugs used in treating glaucoma. See figure on back of card. Aqueous humor is secreted by the ciliary process and flows through the pupillary aperture of the iris into the anterior chamber. It then drains through the trabecular meshwork into the venous sinus of sclera (Schlemm canal). In persons with open-angle glaucoma, elevated intraocular pressure, often resulting from decreased aqueous humor outflow, may lead to the gradual loss of peripheral vision. Drugs can be used to reduce intraocular pressure before irreversible optic nerve damage occurs. Muscarinic receptor agonists (pilocarpine) cause contraction of ciliary muscle fibers that insert near the trabecular meshwork, which opens the trabecular spaces so that aqueous humor drains more easily. Prostaglandins (latanoprost) increase aqueous drainage through the uveoscleral route in which aqueous humor flows through the ciliary muscles into the suprachoroidal space. The β-adrenoceptor blockers (timolol) and the α2-adrenoceptor agonists (apraclonidine) reduce the formation of cyclic adenosine monophosphate (cAMP), a substance that stimulates aqueous humor production. Carbonic anhydrase inhibitors (dorzolamide) reduce formation of bicarbonate, a substance required for aqueous humor secretion. (α = alpha, β = beta.)


Site of action of β-adrenoceptor blockers, carbonic anhydrase

inhibitors, α2-adrenoceptor agonists, and epinephrine

Site of actionof muscarinic

receptor agonists

Site of action ofprostaglandins

CorneaTrabecularmeshwork

Anterior chamber

Schlemm canalIris

Lens

Episcleral vein

Ciliaryprocesses

Circularciliary muscle

Meridionalciliary muscle

Sites of action of drugs used in treating glaucoma. See other side for description.


Atropine(at-roe-peen)

ATROPENSee Pharmacology, 5th ed., Chapter 7, pp. 73-75

Acetylcholine

Atropine

Muscarinic receptors

Heart, smooth muscle, glands

1-6 Atropine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Anticholinergic agent

Pharmacologic Class Muscarinic acetylcholine receptor antagonist

MOA Competitively blocks all muscarinic receptors, increases heart rate and conduction velocity, causes smooth muscle relaxation, and decreases exocrine gland secretion

Clinical Use Treatment (Tx) of bradycardia and atrioventricular block; Tx of irritable bowel symptoms; Tx of anticholinesterase poisoning; antisecretory agent (glycopyrrolate often used for this purpose in surgery); Tx of ocular inflammation (relaxes iris and ciliary muscles)

Special Considerations

Can slow heart rate when first administered, a result of central vagal stimulation

Adverse Effects Tachycardia; mydriasis and cycloplegia; warm, dry, flushed skin; delirium; and hallucinations

Interactions Additive anticholinergic effects with antihistamines (diphenhydramine) and tricyclic antidepressants (amitriptyline); slows absorption of other drugs by delaying gastric emptying

Similar drugs: Darifenacin, dicyclomine, glycopyrrolate, hyoscyamine, ipratropium, oxybutynin, solifenacin, scopolamine, tolterodine, trospium


Bosentan(boe-sen-tan)

TRACLEERSee Pharmacology, 5th ed., Chapter 26, p. 309

Endothelin-1

Bosentan

Endothelin-1 ETA & ETBreceptors

Vascular smooth muscle

1-8 Bosentan Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Vasodilator drug

Pharmacologic Class Endothelin-1 receptor antagonist

MOA Blocks endothelinA (ETA) and endothelinB (ETB) receptors in vascular smooth muscle, causing vasodilation

Clinical Use Treatment of pulmonary arterial hypertension: decreases pulmonary vascular resistance and dyspnea; improves walking distance

Special Considerations Likely to cause birth defects; contraindicated in pregnancy

Adverse Effects Elevated serum aminotransferase levels

Interactions Inhibitors of cytochrome P450 2C9 (CYP2C9) or CYP3A4 (e.g., cyclosporine) elevate bosentan levels; bosentan induces CYP2C9 and CYP3A4 and decreases levels of affected drugs

Similar drugs: Ambrisentan, macitentan


Dobutamine(doe-bue-ta-meen)

DOBUTREXSee Pharmacology, 5th ed., Chapter 8, pp. 86-87

Dobutamine b1, adrenoceptors

Cardiac muscle

Gs � G protein-s, cAMP � cyclic adenosine monophosphate,PKA � protein kinase A

Gs, cAMP, PKA

Ca2�

1-10 Dobutamine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Sympathomimetic; cardiac stimulant

Pharmacologic Class Selective β1-adrenoceptor agonist

MOA Activates β1-receptors > β2-receptors ≫ α1-receptors; increases phosphorylation of calcium channels and calcium Influx; increases cardiac contractility and cardiac output > heart rate

Clinical Use Treatment of acute heart failure and cardiogenic shock

Special Considerations Administered by intravenous infusion; must correct hypovolemia before giving dobutamine

Adverse Effects Tachycardia and arrhythmia

Interactions Synergistic effect on cardiac output with nitroprusside (a vasodilator that decreases cardiac afterload)

Similar drugs: None


Edrophonium(ed-roe-foe-nee-um)

TENSILONSee Pharmacology, 5th ed., Chapter 6, p. 66

Edrophonium

CholinesteraseAcetate � CholineAcetylcholine

1-12 Edrophonium Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Diagnostic agent

Pharmacologic Class Cholinesterase inhibitor

MOA Reversibly inhibits cholinesterase; increases acetylcholine levels at neuroeffector junctions

Clinical Use Diagnosis of myasthenia gravis (MG); increases muscle strength in persons with MG but increases weakness in MG patients treated with excessive doses of a cholinesterase inhibitor; used to reverse effects of curariform-type neuromuscular blocking agents such as rocuronium

Special Considerations Very short-acting after intravenous administration

Adverse Effects Muscarinic effects (e.g., miosis, salivation) can be treated with atropine

Interactions None usually significant

Similar drugs: Neostigmine, physostigmine, pyridostigmine


Epinephrine(e-pi-nef-rin)

ADRENALINSee Pharmacology, 5th ed., Chapter 8, p. 86-88

Epinephrine

a1- & b2-adrenoceptors


b1-adrenoceptors

Cardiac tissue

1-14 Epinephrine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Vasopressor; bronchodilator

Pharmacologic Class Nonselective adrenoceptor agonist

MOA Activates α- and β-receptors, increasing inositol triphosphate and cyclic adenosine monophosphate, respectivelyα1: vasoconstriction and increased blood pressureβ1: increased heart rate, conduction, and contractilityβ2: vasodilation and decreased diastolic blood pressure; bronchodilation

Clinical Use Treatment (Tx) of cardiac arrest; ventricular fibrillation; anaphylactic shock; Tx of asthma and chronic obstructive pulmonary disease; prolongs duration of local anesthetics

Adverse Effects Hypertension; tachycardia; ischemia; hyperglycemia


Similar drugs: Norepinephrine (does not activate β2-receptors significantly)


Epoprostenol(e-poe-pros-te-nole)

FLOLANSee Pharmacology, 5th ed., Chapter 26, pp. 308-309

1-16 Epoprostenol Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Vasodilator

Pharmacologic Class Naturally occurring prostacyclin (PGI2)

MOA Activates prostaglandin IP receptors, causing vascular smooth muscle relaxation and vasodilation; increases pulmonary blood flow and reduces dyspnea

Clinical Use Treatment of pulmonary arterial hypertension (PAH); administered via central venous catheter

Special Considerations Treprostinil is a stable prostacyclin analogue administered by subcutaneous infusion pump that reduces dyspnea and improves physical activity in PAH patients; selexipag is an orally administered prostacyclin IP receptor agonist for treating PAH

Adverse Effects Flushing, hypotension, tachycardia, diarrhea, nausea, vomiting, flulike symptoms


Similar drugs: Treprostinil, selexipag


Metoprolol(meh-toh-pruh-lawl)

LOPRESSORSee Pharmacology, 5th ed., Chapter 9, pp. 96-99

EpinephrineNorepinephrine

Metoprolol

b1-adrenoceptors

Heart

1-18 Metoprolol Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Sympatholytic; antihypertensive

Pharmacologic Class Selective β1-adrenoceptor antagonist

MOA Competitively blocks β-adrenoceptors; decreases heart rate, cardiac output, renin secretion, blood pressure, and myocardial oxygen demand

Clinical Use Treatment of angina and hypertension; post–myocardial infarction to reduce mortality

Special Considerations Given orally or intravenously; lacks local anesthetic or partial agonist activity

Adverse Effects Bronchoconstriction with higher doses because of β2-receptor blockade

Interactions Additive hypotensive effect with nitrates and antihypertensive drugs; additive bradycardia with digoxin; decreases effects of dopamine and dobutamine; unopposed α-adrenergic receptor stimulation with epinephrine and related drugs

Similar drugs: Bisoprolol


Metyrosine(me-tyre-o-seen)

DEMSERSee Pharmacology, 5th ed., Chapter 8, pp. 81-82; Chapter 10, p. 115

Metyrosine

Tyrosine hydroxylaseDihydroxyphenylalanine (DOPA) Dopamine NorepinephrineTyrosine

1-20 Metyrosine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Sympatholytic

Pharmacologic Class Tyrosine hydroxylase inhibitor

M.O.A. Inhibits norepinephrine and epinephrine synthesis

Clinical Use Reduction of blood pressure and heart rate in patients with pheochromocytoma; used preoperatively, or chronically for inoperable tumors; often combined with phenoxybenzamine

Adverse Effects Hypotension, bradycardia

Interactions Additive effects with α- and β-adrenoceptor antagonists

Similar drugs: None


Phenoxybenzamine(fen-ox-i-benz-a-meen)

DIBENZYLINESee Pharmacology, 5th ed., Chapter 9, pp. 93-95


Phenoxybenzamine

a1- > a2-adrenoceptors


1-22 Phenoxybenzamine Autonomic, Autacoid, and Neuromuscular Drugs


Pharmacologic Class Irreversible α-adrenoceptor antagonist

MOA Blocks α1-receptors > α2-receptors; forms covalent bond with α-receptor and causes irreversible receptor blockade

Clinical Use Presurgical treatment of hypertension caused by pheochromocytoma

Special Considerations Effects last several days

Adverse Effects Postural hypotension

Interactions Hypotensive effect increased by β-adrenoceptor blockers and calcium channel blockers

Similar drugs: Phentolamine


Phentolamine(fen-toe-la-meen)

REGITINESee Pharmacology, 5th ed., Chapter 9, pp. 93-94


Phentolamine

a1- & a2-adrenoceptors


1-24 Phentolamine Autonomic, Autacoid, and Neuromuscular Drugs


Pharmacologic Class Nonselective α-adrenoceptor antagonist

MOA Competitive, reversible antagonist of α1- and α2-receptors causing vasodilation

Clinical Use Counteracts vasoconstriction caused by accidental injection or extravasation of epinephrine and other vasoconstrictors; control of blood pressure during surgery for pheochromocytoma

Special Considerations Parenteral administration only; short duration of action

Adverse Effects Hypotension

Interactions Severe hypotension if given with epinephrine; blocks effects of α-adrenoceptor agonists

Similar drugs: Phenoxybenzamine


Phenylephrine(fen-il-ef-rin)

NEO-SYNEPHRINESee Pharmacology, 5th ed., Chapter 8, p. 89

Phenylephrine a1-adrenoceptors

Vascular smooth muscle Muscle contraction

PKC � protein kinase C, iP3 � inositol triphosphate

Sarcoplasmicreticulum

Gq, PKC, iP3Ca2�

1-26 Phenylephrine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Vasoconstrictor; decongestant

Pharmacologic Class Selective α1-adrenoceptor agonist

MOA Activates α1-receptors, increasing inositol triphosphate via protein kinase C activation, and causing release of calcium and contraction of vascular smooth muscle and vasoconstriction

Clinical Use Nasal and ocular decongestant; treatment of drug-induced hypotension and spinal shock; dilation of pupil for ophthalmoscopy; local hemorrhoid treatment

Special Considerations Ocular administration causes mydriasis without cycloplegia (paralysis of accommodation)

Adverse Effects Rebound nasal congestion if used topically more than 3 days; hypertension

Interactions May cause severe hypertension if given with monoamine oxidase inhibitors; vasopressor effect increased by tricyclic antidepressants

Similar drugs: Norepinephrine, pseudoephedrine


Pilocarpine(pye-loe-car-peen)

SALAGENSee Pharmacology, 5th ed., Chapter 6, p. 66

Pilocarpine Muscarinic M3 receptors

Salivary glands and ocular muscles

Gland secretion

Muscle contraction

Gq, PKC, IP3

PKC � protein kinase C, lP3 � phospho-inositol

1-28 Pilocarpine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Antiglaucoma agent; sialagogue

Pharmacologic Class Muscarinic acetylcholine receptor agonist

MOA Activates muscarinic receptors in ciliary muscle, increasing aqueous humor outflow; activates muscarinic receptors in salivary gland, increasing salivation

Clinical Use Treatment of glaucoma (topical ocular administration) and dry mouth (xerostomia) by oral administration

Special Considerations

Useful in patients with xerostomia caused by radiation of head and neck and Sjögren syndrome (arthritis, dry eyes, dry mouth)

Adverse Effects Miosis, blurred vision (accommodative spasm) caused by excessive contraction of iris sphincter and ciliary muscles, respectively

Interactions Additive effects with other cholinergic drugs; effects decreased by atropine and other anticholinergic drugs

Similar drugs: Cevimeline


Pralidoxime(pral-i-dox-ime)

PROTOPAMSee Pharmacology, 5th ed., Chapter 6, p. 70

1-30 Pralidoxime Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Organophosphate antidote

Pharmacologic Class Cholinesterase reactivator

MOA Binds phosphorus of organophosphate and breaks bond with cholinesterase

Clinical Use Treatment of organophosphate toxicity (used to reverse muscle weakness)

Special Considerations Give as soon as possible after organophosphate exposure (before aging of organophosphate-cholinesterase bond prevents reactivation)

Adverse Effects When treating organophosphate poisoning, it is difficult to differentiate the toxic effects of pralidoxime from those produced by atropine or organophosphate compounds

Interactions When used with atropine, signs of atropinization occur earlier than when atropine is used alone

Similar drugs: None


Propranolol(proe-pran-oh-lol)

INDERALSee Pharmacology, 5th ed., Chapter 9, pp. 96-99; Chapter 32, p. 32-35


Propranolol

b1- & b2-adrenoceptors

Cardiac and smooth muscle

1-32 Propranolol Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Sympatholytic; antihypertensive

Pharmacologic Class Nonselective β-adrenoceptor antagonist

MOA Competitively blocks β1- and β2-receptors; decreases heart rate, cardiac output, blood pressure, myocardial oxygen demand

Clinical Use Treatment of angina, cardiomyopathy, hypertension, thyrotoxicosis, and benign tremor; migraine prophylaxis

Special Considerations Highly lipophilic, causing central nervous system side effects; local anesthetic activity prevents ocular use

Adverse Effects Bronchoconstriction; inhibits glycogenolysis; nightmares and mood depression

Interactions Additive hypotensive effect with nitrates and antihypertensive drugs; additive bradycardia with digoxin; decreases effects of dopamine and dobutamine; causes unopposed α-adrenoceptor stimulation with epinephrine and related drugs

Similar drugs: Nadolol, pindolol, timolol


Pseudoephedrine(soo-doe-e-fed-rin)

SUDAFEDSee Pharmacology, 5th ed., Chapter 8, pp. 90-91

1-34 Pseudoephedrine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Decongestant

Pharmacologic Class Indirect- and direct-acting adrenoceptor agonist

MOA Increases release of norepinephrine and directly activates adrenoceptors, causing vasoconstriction and cardiac stimulation

Clinical Use Administered orally as nasal decongestant for allergic and viral rhinitis and sinusitis

Special Considerations Use is restricted to prevent diversion for methamphetamine synthesis

Adverse Effects Tachycardia; increased blood pressure; central nervous system stimulation

Interactions Concurrent use with monoamine oxidase (MAO) inhibitors causes severe hypertension; urine acidification or alkalinization increases or decreases excretion, respectively

Similar drugs: Norepinephrine, phenylephrine


Pyridostigmine(peer-i-doe-stig-meen)

MESTINONSee Pharmacology, 5th ed., Chapter 6, p. 68

Pyridostigmine

CholinesteraseAcetate � CholineAcetylcholine

1-36 Pyridostigmine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Antimyasthenic agent

Pharmacologic Class Cholinesterase inhibitor; indirect-acting cholinergic agonist

MOA Reversibly inhibits cholinesterase; increases acetylcholine levels at neuroeffector junctions

Clinical Use Treatment of myasthenia gravis (severe muscle weakness); reversal of nondepolarizing neuromuscular blockers such as vecuronium during surgery

Special Considerations Muscarinic effects blocked by atropine

Adverse Effects Muscarinic effects (e.g., miosis, salivation)

Interactions Prolongs effects of succinylcholine; effects reduced by atropine, antidepressants, phenothiazine drugs, quinidine, and other drugs with anticholinergic effects

Similar drugs: Edrophonium, neostigmine


Rocuronium(roe-cue-roe-nee-um)

ZEMURONSee Pharmacology, 5th ed., Chapter 7, pp. 76-78

Acetylcholine

Rocuronium

Nicotinic receptors

Skeletal neuromuscularjunction

1-38 Rocuronium Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Paralytic agent

Pharmacologic Class Nondepolarizing neuromuscular blocking agent

MOA Competitively blocks nicotinic receptors in skeletal muscle; has little effect on autonomic ganglia

Clinical Use Skeletal muscle relaxation for intubation, surgery, and electroconvulsive therapy; 30- to 60-min duration of action

Special Considerations Effects reversed by neostigmine, pyridostigmine, and edrophonium; effects more rapidly reversed by sugammadex

Adverse Effects Respiratory muscle paralysis and apnea

Interactions Effects potentiated by anesthetics, Ca2+ channel blockers, tetracycline, and aminoglycoside antibiotics

Similar drugs: Vecuronium, pancuronium


Sildenafil(sil-den-a-fil)

VIAGRASee Pharmacology, 5th ed., Chapter 6, p. 70

Sildenafil

Type 5 Phosphodiesterase5�-GMP (inactive)Cyclic GMP

1-40 Sildenafil Autonomic, Autacoid, and Neuromuscular Drugs


Pharmacologic Class Phosphodiesterase inhibitor

MOA Inhibits type-5 phosphodiesterase breakdown of cyclic guanosine monophosphate and increases vasodilation in corpus cavernosum evoked by acetylcholine-mediated release of nitric oxide

Clinical Use Treatment (Tx) of erectile dysfunction; Tx of pulmonary arterial hypertension

Special Considerations Tadalafil and vardenafil also used to treat urinary symptoms of benign prostatic hyperplasia; tadalafil also approved for pulmonary arterial hypertension

Adverse Effects Headache; nasal congestion; back pain; visual disturbances; concurrent use with organic nitrates can cause profound hypotension, reflex tachycardia, angina, and death

Interactions Potentiates vasodilation produced by organic nitrates; serum levels increased by cytochrome P450 3A4 (CYP3A4) inhibitors

Similar drugs: Avanafil, tadalafil, vardenafil


Solifenacin(sol-ee-fen-a-sin)

VESICARESee Pharmacology, 5th ed., Chapter 7, pp. 75-76

Acetylcholine

Solifenacin

Muscarinic receptors

Urinary bladder muscle

1-42 Solifenacin Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Overactive bladder (OAB) agent

Pharmacologic Class Muscarinic receptor antagonist

MOA Competitively blocks muscarinic acetylcholine receptors in the urinary bladder and elsewhere; relaxes urinary bladder smooth muscle

Clinical Use Treatment of OAB: relieves urgency, incontinence, and frequency while increasing voided volume per micturition

Special Considerations Once-daily oral administration with or without food; oxybutynin available as a topical gel for OAB

Adverse Effects Dry mouth, constipation, blurred vision (accommodation abnormalities), urinary retention, and dry eyes

Interactions Metabolized by CYP3A4; strong inhibitors of CYP3A4 (ketoconazole) increase serum levels, and lowest dose of solifenacin should be employed if given concurrently

Similar drugs: Darifenacin, oxybutynin, tolterodine, trospium


Succinylcholine(sux-sin-il-koe-leen)

ANECTINESee Pharmacology, 5th ed., Chapter 7, p. 78

Acetylcholine

Succinylcholine

Nicotinic receptors

Skeletal neuromuscularjunction

Prolongeddepolarization

1-44 Succinylcholine Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Paralytic agent

Pharmacologic Class Depolarizing neuromuscular blocker

MOA Binds to nicotinic receptors, causing persistent depolarization of skeletal muscle and muscle paralysis; rapidly metabolized by plasma cholinesterase; short duration of action (5-10 min)

Clinical Use Short-term skeletal muscle relaxation for intubation and surgery; often preferred for intubation owing to short duration of action

Special Considerations Causes transient muscle fasciculations; effects are not reversed by neostigmine or edrophonium (unlike those of rocuronium and other curariform drugs)

Adverse Effects Respiratory muscle paralysis and apnea, especially in persons with rare atypical cholinesterase

Interactions Neuromuscular blockade enhanced by aminoglycoside antibiotics, clindamycin, amphotericin B, quinidine, and cholinesterase inhibitors

Similar drugs: None


Tamsulosin(tam-soo-loe-sin)

FLOMAXSee Pharmacology, 5th ed., Chapter 9, pp. 95-96


Tamsulosin

a1A-adrenoceptors

Prostate & bladder muscle

1-46 Tamsulosin Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Urologic agent

Pharmacologic Class Uroselective α1-adrenoceptor antagonist

MOA Competitively blocks α1A-receptors in bladder and prostate; relaxes prostatic and bladder smooth muscle and facilitates bladder emptying

Clinical Use Treatment of urinary tract symptoms of benign prostatic hyperplasia: urinary frequency, urgency, and nocturia (the need to urinate more frequently at night)

Special Considerations Alfuzosin, silodosin, and tamsulosin are not indicated for treatment of hypertension

Adverse Effects Dizziness; headache; postural hypotension

Interactions Cimetidine may increase blood levels and effects

Similar drugs: Alfuzosin, silodosin


Terazosin(ter-az-oh-sin)

HYTRINSee Pharmacology, 5th ed., Chapter 9, pp. 94-96


Terazosin

a1-adrenoceptors

Smooth muscle

1-48 Terazosin Autonomic, Autacoid, and Neuromuscular Drugs

Therapeutic Class Antihypertensive agent; urologic agent

Pharmacologic Class α1-adrenoceptor antagonist

MOA Competitively blocks α1A and α1B-receptors; relaxes arteriolar smooth muscle and decreases vascular resistance and blood pressure; relaxes prostatic and bladder smooth muscle to facilitate emptying of bladder

Clinical Use Treatment of hypertension and urinary symptoms caused by prostatic hyperplasia

Special Considerations Less selective for prostatic smooth muscle than selective α1A blockers such as alfuzosin, silodosin, and tamsulosin

Adverse Effects Hypotension; first-dose syncope; start with low dose and gradually increase

Interactions Additive hypotensive effect with diuretics and other antihypertensive drugs

Similar drugs: Doxazosin

I Autonomic, Autacoid, and Neuromuscular DrugsAtropineBosentanDobutamineEdrophoniumEpinephrineEpoprostenolMetoprololMetyrosinePhenoxybenzaminePhentolaminePhenylephrinePilocarpinePralidoximePropranololPseudoephedrinePyridostigmineRocuroniumSildenafilSolifenacinSuccinylcholineTamsulosinTerazosin

1-1 section i · 1-6 atropine autonomic, autacoid, and neuromuscular drugs therapeutic...

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