Respiratory Pharmacology

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Epinephrine

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Properties - stimulates both α (vasoconstriction - esp skin, mucosa and kidneys) and β (bronchodilatation) receptors. β2 stimulation may also decrease mast cell secretions. vital capacity increases due to relief of bronchial mucosal congestion. not effective orally, rapidly absorded IM or SQ.
Indications - acute asthmatic attacks, hypersensitivity reactions, prolongation of infiltration anesthetic action, topical hemostatic effect
SE, Tox - anxiety, termor, palpitations, tachycardia, headache, diaphoresis, pallor
CI - HTN, hyperthroid, ischemic heart disease, cerebrovascular insufficiency. don't use if older than 60 unless asthma is intractable.

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Ephedrine

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Properties - stimulates both α and β receptors and increases the release of NE. vasoconstriction/cardiac stimulation --> increase pulse pressure. CNS stimulant. Rapidly absorbed PO. Compared to epi - longer duration of action, more central effects, lower potency.
Indications - chronic asthma (rarely used now), mydratic (aqueously).
SE, Tox - CNS stimulation, increased PVR.

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Isoproterenol

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Properties - stimulates β receptors. all smooth muscle is relaxed and PVR is lowered in skeltal, renal, and mesenteric vascular beds. rapidly absorded after inhalation.
Indications - relieves respiratory distress in severe asthmatic attacks but rarely used now that there's more selective agents.
SE, Tox - acute toxicity less than with epi. tachycardia, headache, flushing, nausea, dizziness, diaphoresis. anginal pain/cardiac arrhythmias. tolerance can occur.

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Metaproterenol

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Properites - β2 selective. relaxes smooth muscle of bronchi, uterus, skeletal muscle vasculature, decreases airway resistance. resistant to COMT methylation. PO or inhaled, duration up to 4 hours.
Indications - bronchodilator in treatment of asthma, reversible bronchospasm.
SE, Tox - tachycardia, hypertension, nervousness, termor, palpitations, n/v. caution in pts with severe HTN, coronary artery disease, CHF, hyperthroid. tolerance less like compared to inhaled isoproterenol.

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Terbutaline

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Properties - β2 selective when given orally but causes cardio effects similar to isoproterenol when given SQ. resistant to COMT methylation.
Indications - only β2 agonist used parenterally for tx of status asthmaticus.
SE, Tox - oral causes tremor. dizziness, nervousness, fatigue, tinnitus, palpitations rare. SQ causes same effects as epi.

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Salmeterol

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Properties - β2 selective. longer actinging.
Indications - asthma prophylaxis.

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Albuterol

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Properties - similar to terbutaline. β2 selective. aviable as oral and aersol preparation. peak effect 30-40 min with 3-4 hour duration.
Indications - reversible obsructive airway disease.
SE, Tox - nervousness, termor, headache, insomnia, weakness, dizziness, tachycardia, palpitations. use in caution in pts wtih coronary artery insufficiency, HTN, hyperthroid, DM and pts recieving MAO-I or TCAs.

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Theophylline

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Properties - inhibits phosphodiesterase --> increased cAMP. relaxes bronchial smooth muscles --> increased VC, potent CNS stimulant, imporves diaphragmatic contractility. positive inotropic action. increases water and electrolyte excretion. oral, rectal, or parental. distributed into all compartments, 60% pro bound.
Met/Excr- liver met, t1/2 = 8 hrs.
Indications - bronchodilator in asthma and COPD, improve diaphragmatic function in COPD, reduceds prolonged apnea in preterm infants.
SE, Tox - oral causes headache, nervousness, dizziness, n/v, epigastric pain. iv causes cardiac arrhythmias (blocks adenosine receptors which then increases AV nodal conduction), hypotension, cardiac arrest and seizures.
in children, CNS stimulation, diuresis, fevers.
monitor serumm levels (tox at >20 mg/L, benefit at 7-10).
Drug Interactions - barbituates, phenytoin, smoking increase its met. allopurinol, propranolol, cimetidine, erthromycine, influences vaccine decrease its met.

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Cromolyn Sodium/Nedocromil

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Properties - inhibits the degranulation of mast cells preventing the realse of histamine and other autacoids after immunologic and nonimmunologic stimulation. inhaled because of low oral absorption.
Met/Excr - excreted unchanged within a few days. maximal levels reached within minutes with t1/2 = 1 hr. response observed within weeks.
Indications - prevent asthma attacks esp. in cold and exercise induced asthma. most protective n kids with chronic unstable asthma. can also be used as a nasal spray for allergic rhinitis.
SE, Tox - seen in less than 5% of pts. sore thraot, cough, dry mouth most common. urticaria, maculopapular dermatitis, gastroenteritis.

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Prednisone/Prednisolone

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Class - corticosteroids. reduce inflammation and edema and potentiate the bronchodilating effects of adrenergic agonists. inactivate NF-kB the transcription factor that induces the production of TNF-α.
Indications - severe chronic and acute bronchospasm.
SE, Tox - suppression of growth, osteoporosis, aggravation of diabetes, aseptic bone necrosis, adrenocortical suppresions.

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Beclomethasone dipropionate

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Class - corticosteroids. reduces inflammation and edema na dpotentiates the bronchodilating effects of adrenergic agonists.
Properties - inhaled in metered doses. highly potent. only minor systemic absorption and rapid metabolism so it has no effect on the HPA axis.
Indications - substiute for oral preparations in selected individuals with severe steroid-dependent asthma.
SE, Tox - oropharyngeal and laryngeal candidal infection. hoarseness, sore throat, dry mouth.

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Atropine/Ipratropium Bromide

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Properties - block muscarinic receptors thereby inhibiting aceycholine-induced bronchoconstriction.
Indications - in asthma pts unresponsive to adrenergic agents and methylxantihines. bromidey is often used in COPD because it also reduced secretions.
SE, Tox - drowsiness, sedation, dry mouth, blurred vision, urinary retenion, constipation. not as pronounced with ipratropium because it does not cross the BBB.

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Zileuton

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Class - anitleukotriene
Properties - inhibits 5-lipoxygenase therefore blocks synthesis of leukotrienes. use with corticosteroids.
Indications - prophylaxis of asthma.
SE, Tox - diarrhea, headache, increased risk of infections.

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Zafirlukast

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Blocks LTD4 leukotriene receptors. LTD4 is a receptors function in bronchoconstriction, vasoconstriction, contraction of smooth muscle and increased vascular permeability.

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First Generation H1 Blockers

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Examples - Diphenhydramine, dimenhydrinate, chlorpheniramine.
Indications - Allergy, motion sickness, sleep aid.
Toxicity - Sedation, antimuscarinic, anti-α-adrenergic.

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Second Generation Histamine Blockers

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Examples - Loaratidine, fexofenadine, desloratadine.
Indications - Allergy
Toxicity - far less sedating than first generation.