PHARMACOLOGY

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PHARMACOLOGY

• Respiratory drugs

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OBJECTIVES

• Identify the classes of drugs used to improve
  respiratory function.
• Identify the uses and varying actions of these
  drugs.
• Identify how these drugs are absorbed,
  distributed, metabolized, and excreted.
• Identify drug interactions and adverse reactions
  to these drugs.

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DRUGS AND THE RESPIRATORY SYSTEM

• The respiratory system takes in oxygen and expels
  carbon dioxide.
• Drugs used to improve respiratory function
  include methylxanthines, expectorants,
  antitussives, mucolytics, and decongestants.

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METHYLXANTHINES

• Used to treat breathing disorders.
• Types of methylxanthines include anhydrous
  theophylline and its derivative salts,
  aminophylline, oxtriphylline, and theophylline
  sodium glycinate.

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METHYLXANTHINES

• Pharmacokinetics
• Vary according to drug, dosage form, and
  administration route.
• Absorbed rapidly and completely 60
  protein-bound in adults readily crosses the
  placental barrier secreted in breast milk
  metabolized primarily by the liver 10 excreted
  unchanged in the urine.

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METHYLXANTHINES

• Pharmacodynamics
• Decrease airway reactivity and relieve
  bronchospasm by relaxing bronchial smooth muscle.
• In nonreversible obstructive airway disease the
  drug increases the sensitivity of the brains
  respiratory center to CO2 and to stimulate the
  respiratory drive.

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METHYLXANTHINES

• In chronic bronchitis and emphysema, these drugs
  decrease fatigue of the diaphragm and improve
  ventricular function.

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METHYLXANTHINES

• Pharmacotherapeutics
• Used to treat asthma, chronic bronchitis,
  emphysema, and neonatal apnea.

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METHYLXANTHINES

• Drug interactions
• Smoking increases elimination, decreasing serum
  concentrations and effectiveness.
• Taking adrenergic stimulants or drinking
  beverages that contain caffeine may result in
  additive adverse reactions.
• Phenobarbital, phenytoin (Dilantin), rifampin,
  and carbamazepine (Tegretol) reduce levels.

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METHYLXANTHINES

• Receiving halothane, enflurane, isoflurane, and
  methoxyflurane increases the risk of cardiac
  toxicity.
• May reduce the effects of lithium by increasing
  its rate of excretion.
• Thyroid hormones may reduce levels.
• Many drugs can increase levels resulting in
  toxicity.

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OTHER DRUGS

• Two other drugs used to relieve bronchospasm in
  acute asthma attacks include short-acting
  beta2-adrenergic agonists (Albuterol) and
  anticholinergics (Atropine).
• Another drug used prevent asthma attacks (not
  treat acute asthma attacks) is cromolyn sodium
  (Intal, Nasalcrom).

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EXPECTORANTS

• These drugs thin mucous so its cleared more
  easily out of airways.
• The most commonly used expectorant is guaifenesin
  (Robitussin).

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EXPECTORANTS

• Pharmacokinetics
• Absorbed through the GI tract metabolized by the
  liver excreted primarily by the kidneys.

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EXPECTORANTS

• Pharmacodynamics
• By increasing the production of respiratory tract
  fluids, expectorants reduce the thickness,
  adhesiveness, and surface tension of mucous,
  making it easier to clear from the airways.

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EXPECTORANTS

• Pharmacotherapeutics
• Used for the relief of coughs from colds, minor
  bronchial irritation, bronchitis, influenza,
  sinusitis, bronchial asthma, emphysema, and other
  respiratory disorders.
• May be taken with antitussives, analgesics,
  antihistamines, or decongestants.

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EXPECTORANTS

• Drug interactions
• Administration with anticoagulants may increase
  the risk of bleeding.

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ANTITUSSIVES

• Suppress or inhibit dry, nonproductive coughing.
• Include benzonatate (Tessalon), codeine,
  dextromethorphan hydrobromide, and hydrocodone
  bitartrate.

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ANTITUSSIVES

• Pharmacokinetics
• Absorbed well through the GI tract metabolized
  by the liver excreted in the urine.

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ANTITUSSIVES

• Pharmacodynamics
• Act in slightly different ways.
• Benzonatate acts by anesthetizing stretch
  receptors throughout the bronchi, alveoli, and
  pleura.
• The others suppress the cough reflex by direct
  action on the cough center in the medulla of the
  brain.

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ANTITUSSIVES

• Pharmacotherapeutics
• Used to treat a serious, nonproductive cough that
  interferes with a patients ability to rest and
  perform ADLs.
• Benzonatate relieves cough caused by pneumonia,
  bronchitis, the common cold, and COPD.
• Also used during diagnostic procedures.

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ANTITUSSIVES

• Dextromethorphan is the most widely used because
  of its effectiveness and few adverse reactions.
• Narcotic antitussives (codeine and hydrocodone)
  are used to treat the intractable cough
  associated with lung CA.

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ANTITUSSIVES

• Drug interactions
• Dextromethorphan, codeine and hydrocodone may
  cause excitation, an extreme elevated temp.,
  hypertension, hypotension, and coma when taken
  with MAO inhibitors.
• Codeine may cause CNS depression when taken with
  other CNS depressants.

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MUCOLYTICS

• Act directly on mucous, breaking down sticky,
  thick secretions so theyre more easily
  eliminated.
• Acetylcysteine (Mucomyst) is the only thiol
  compound mucolytic used clinically in the U.S.

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MUCOLYTICS

• Pharmacokinetics
• When inhaled is absorbed from the pulmonary
  epithelium when taken orally is absorbed from
  the GI tract.
• Metabolized in the liver excretion is unknown.

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MUCOLYTICS

• Pharmacodynamics
• Decreases the thickness of respiratory tract
  secretions by altering the molecular composition
  of mucous.

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MUCOLYTICS

• Pharmacotherapeutics
• Used with other therapies to treat patients with
  abnormal or thick mucous secretions such as those
  with bronchitis, emphysema, cystic fibrosis, or
  atelectasis.
• Used as a bronchial study prep.
• Is the antidote for acetaminophen overdose.

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MUCOLYTICS

• Drug interactions
• Activated charcoal decreases effectiveness,
  therefore, when using drug to treat acetaminophen
  overdose, remove activated charcoal from the
  stomach.

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DECONGESTANTS

• Classified as systemic or topical.
• Systemic decongestants stimulate the sympathetic
  nervous system to reduce swelling of the
  respiratory tracts vascular network.
• Drugs include ephedrine, phenylpropanolamine,
  and pseudoephedrine (Sudafed).

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DECONGESTANTS

• When applied directly to swollen mucous membranes
  of the nose, topical decongestants provide
  immediate relief from nasal congestion.
• These drugs include ephedrine, epinephrine,
  phenylephrine, Prototype naphazoline (Afrin),
  oxymetazoline, tetrahydrozoline, and
  xylometazoline.

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DECONGESTANTS

• Pharmacokinetics
• Properties vary among drugs.
• Systemic drugs when taken orally are readily
  absorbed from the GI tract widely distributed
  throughout the body, including CSF, placenta, and
  breast milk metabolized slowly and incompletely
  in the liver excreted largely unchanged in the
  urine.

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DECONGESTANTS

• Topical decongestants act directly on the alpha
  receptors of the vascular smooth muscle in the
  nose, causing the arterioles to constrict,
  resulting in very little of the drug being
  absorbed.

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DECONGESTANTS

• Pharmacodynamics
• Systemic decongestants cause vasoconstriction by
  stimulating alpha-adrenergic receptors in the
  blood vessels in the nasal mucosa.
• Topical decongestants work the same as systemic
  ones, however, the reduced blood flow to the
  nasal mucous membranes reduces swelling.

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DECONGESTANTS

• Pharmacotherapeutics
• Used to relieve the symptoms of swollen nasal
  membranes resulting from hay fever, allergic
  rhinitis, vasomotor rhinitis, acute coryza,
  sinusitis, and the common cold.
• Systemic decongestants are frequently given with
  antihistamines, antipyretics-analgesics,
  antitussives, and expectorants.

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DECONGESTANTS

• Topical decongestants provide two major
  advantages over systemics minimal adverse
  reactions and rapid symptom relief.

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DECONGESTANTS

• Drug interactions
• Because of vasoconstriction, topical drug
  interactions seldom occur.
• Increased CNS stimulation may occur when taken
  with other sympathomimetic drugs.
• Taken with MOA inhibitors may cause severe
  hypertension or a hypertensive crisis.
• Alkalinizing drugs may increase the effects of
  pseudoephedrine.