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Drugs - Autonomic Nervous System + Respiratory System

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usmlevan's version from 2015-04-21 06:05

Sympathomimetics

DrugAction
Epinephrineβ1&β2 > α1, α2
Norepinephrineα1
Isoproterenolβ1&β2
Phenylpherineα1, α2
Albuterolβ2
Dobutamineβ1
Dopaminemedium dose = β1, high dose = α1 (shock & renal failure)
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ANS Drugs

 

Cholinomimetics (stim parasymp, sweating, and somatic activity)

 

Direct agonists
DrugApplicationNotes
Bethanecholpostop and neurogenic ileus and urinary retentionactivates bowel/bladder smooth muscle, resistant to AchE
Carbacholglaucoma, pupillary contraction-
Pilocarpinestim sweat, tears, salivacontracts ciliary muscle of eye (open angle), pupillary sphincter (narrow angle), resistant to AchE
Methacholinechallenge test for asthma diagstim muscarinic receptors in airway
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Indirect agonists (anticholinesterases)
Poisoning sxs - Diarrhea, Urination, Miosis, Bronchospasm, Bradycardia, Excitation of skeletal muscle and CNS, Lacrimation, Sweating, Salivation (and abdom cramping) = DUMBBELSS -> atropine + pralidoxime is antidote.
DrugApplicationNotes
Neostigminepostop and neurogenic ileus and urinary retension, myasthenia gravis, postop reversal of NMJ block↑ endo ACh, no CNS entry
Pyridostigminemyasthenia gravis (long-acting)↑ endo ACh, ↑ strength, no CNS entry
Edrophoniumdiag myasthenia gravis (super short acting)↑ endo ACh
Physostigmineglaucoma, atropine overdose↑ endo ACh, crosses BBB
Echothiophateglaucoma↑ endo ACh
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Muscarinic antagonists (antagonizes parasymp, sweat glands)
DrugOrgan systemNotes
Atropine, homatropine, tropicamideeyeproduce mydriasis and cycloplegia (paralysis of ciliary muscles)
BenztropineCNSParkinson's disease
ScopolamineCNSmotion sickness
Ipratropiumrespiratoryasthma, COPD
OxybutyninGUreduce urgency and bladder spasms
Methscopolamine, pirenzepine, propanthelineGIpeptic ulcer treatment
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Nicotinic antagonists - Hexamethonium
Use -> ganglionic blocker, prevent vagal reflex responses to changes in BP (reflex tachy due to NE)
Toxicity -> orthostatic HTN, blurred vision, constipation, sexual dysfunction

 

Sympathomimetics (action similar to NE)
Direct sympathomimetics
DrugApplicationMechanism/selectivity
Epinephrineanaphylaxis, glaucoma (open angle), asthma, hypotensionα1, α2, β1, β2. selective for β1 at low doses
NEhypotensionα1, α2 > β1
IsoproterenolAV blockβ1=β2
Dopamineshock (↑ renal perfusion), heart failureD1 = D2 >β>α, inotropic (↑ muscle contraction strength) and chronotropic (↑ HR)
Dobutamineshock, heart failure, cardiac stress testβ1 > β2, inotropic but not chronotropic
Phenylephrinepupillary dilation, vasoconstriction, nasal decongestα1 > α2
Metaproterenol, albuterol, salmeterol, terbutalinemeta and albuterol for acute asthma, salm for long-term asthma, terb to reduce premature uterine contractionsselective β2 agonists (β2 > β1)
Ritodrinereduce premature uterine contractionsβ2
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Indirect sympathomimetics
DrugApplicationMechanism/selectivity
Amphetaminenarcolepsy, obesity, ADHDreleases stored catecholamines
Ephedrinenasal decongestion, urinary incontinence, hypotensionreleases stored catecholamines
Cocainevasoconstriction and local anesthesiauptake inhibitor
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Sympathoplegics (inhibits post-ganglionic SNS function)
Clonidine, a-methyldopa - centrally acting α2-agonists, ↓ central adrenergic outflow
Application - treat hypertension, esp with renal disease (you can ↓ BP without ↓ blood flow to kidney)

 

α-blockers
DrugApplicationToxicity
(non-selective)
Phenoxybenzamine (irreversible) and phentolamine (reversible)pheochromocytoma (use irreversible blocker before removing tumor, since high levels of released catecholamines will not be able to overcome blockage)orthostatic hypotension, reflex tachyardia
(α1-selective - zosin ending)
Prazosin, terazosin, doxazosinhypertension, urinary retention in BPH1st dose orthostatic hypotension, dizziness, headache
(α2-selective)
Mirtazapinedepressionsedation, ↑ serum cholesterol, ↑ appetite
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β-blockers
Toxicity - impotence, asthma exacerbation, CV(bradycardia, AV block, CHF), CNS (sedation, sleep alterations), caution in diabetics
Mnemonic - drugs A-M are β1 selective, drugs N-Z are nonselective (exceptions are labetalol and carvedilol, the only 2 that are both α and β blockers)
DrugSelectivity of antagonism
propranololβ1=β2
timolol β1=β2
nadololβ1=β2
pindololβ1=β2 (partial β agonist)
labetalolβ1=β2 (also a blocker)
acebutololβ1>β2 (partial β agonist)
betaxololβ1>β2
esmololβ1>β2 (short acting)
atenololβ1>β2
metoprololβ1>β2
carvedilolα = β
labetalolα = β
pindolol, acetutololpartial β agonists
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Application of β-blockers
ApplicationEffect
hypertension↓ CO, ↓ renin (b-receptor blockade on JGA cells)
angina pectoris↓ HR, ↓ contractility -> result in ↓ O2 consumption
MI↓ mortality
superior vent tachy (propranolol, esmolol)↓ AV conduction velocity (class II antiarrhythmic)
CHFslows progression of chronic heart failure
glaucoma (timolol)↓ secretion of aqueous humor
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Pulmonary System Drugs

H1 blockers

DrugMechanismUseSE
Diphenhydramine (benadryl), Chloropheniramine1st gen, reversible H1 histamine receptor blockerallergies, sleep aidcross BBB --> sedation
Loratadine2nd genration, reversible H1 histamine receptor blockerallergyno sedation
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Asthma drugs

DrugMechanismUseSE
Albuterolβ2 agonist, vasodilation, relax smooth muscleacute asthma attachn/a
Salmeterolβ2 agonist, vasodilation, relax smooth musclelong acting, for prophylaxistremors and arrhythmias
Theophyllinebronchodilation by ↓ phosphodiesterase = ↑cAMPrarely used for asthma b/c narrow TIcardiotoxicity, neurotoxocity, blocks adenosine
Ipratropiumblocks ACh receptorsasthma & COPD, long actingn/a
Cromolyn sodiumbinds to mast cells and blocks histamine releaseprophylaxis for asthman/a
Beclomethasone/Prednisoneglucocorticoids, ↓ IL; ↓ NF-kB = ↓ immune response1st line therapy for chronic asthmacushing's syndrome
Montelukastblocks LTC4,LTD4,LTE4 receptorsaspirin induced asthman/a
Zileutonblocks LOX = ↓ leukotrienes (LTC4,LTD4,LTE4)aspirin induced asthman/a
Omalizumabmab against IgEused in asthma resistant to inhaled steroids and long-acting β2 agonist.
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Others

DrugMechanismUseSE
Guaifenesinthins mucus, does not suppress cough reflex, found in Robitussinthinning mucusn/a
N-acetylcysteineloosen mucus plugs in cystic fibrosis patients, also antidote for acetaminophen OD. Regenerates glutathione~cystic fibrosis ptxn/a
Bosentan↓ endothelin-1 = causes vasodilation (endothelin = secreted by endothelium cells when damaged to induce vasoconstriction, limit loss of O2)tx for pulmonary hypertensionn/a
Prostaglandins↓ bronch tone and ↓ vaso tone (vasodilation)
Dextromethorphanprevents cough (β NMDA glutamate receptors), codeine analog. "Mucinex DM" --> DM = dextromethorphanstop coughabuse potential, if OD = tx w/ Naloxone
Pseduoephedrineα-agonist (makes you dry)nasal decongestants --> ↓ edema. Also a stimulantHTN, CNS anxiety
MethacholineACh receptor agonistasthma challenge test (asthma ptx react to low doses vs. normal ptx need higher doses)n/a
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