Pharmacology Unit 7 Respiratory, Antihistaminic, and GI Drugs

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Pharmacology Unit 7 Respiratory, Antihistaminic, and GI Drugs
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Pharmacology Unit Respiratory Antihistaminic GI Drugs
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Pharmacology Unit 7 Respiratory, Antihistaminic, and GI Drugs
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  1. iii) Anticholinergic – ipratropium (Atrovent®)
    • (1) Bronchodilator
    • (a) Blocks muscarinic receptors
    • (b) Not drying
    • (i) Probably due to poor lipid solubility
    • (2) Systemic side effects NOT SEEN SO FAR
    • (3) Currently recommended for COPD but not asthma
    • (a) May have value in asthma as adjunct
  2. 2) Respiratory drugs with Anti-inflammatory Effects- what are they (3 types) and when would they be used?
    • a) Asthma Prophylactics – cromolyn (Aaranene®, Intal®), nedocromil (Tilade®). AKA: Mast Cell Stabilizers (Basophil)/ Histamine Release Inhibitors
    • i) Therapeutic Uses: helps prevent asthma attack from occurring – cannot treat symptoms once they have appeared. Takes 2 weeks to become effective w/ 4-6 doses/day
    • (1) Atopic asthma
    • (2) Exercise induced asthma
    • (3) Some cases of intrinsic asthma
    • (a) Not used for bronchitis/emphysema
    • (b) Advantage: no cardiac stimulation
    • ii) MOA: Prevents release of histamine & other mediators
    • (1) Is therefore “anti-inflammatory”
    • (2) Interferes w/ bronchoconstriction that is histamine based
    • iii) Caution
    • (1) Inhalation occasionally causes bronchospasm, throat irritation, headache and unpleasant taste
    • b) Leukotriene Receptor Antagonist (/Modifiers): montelukast (Singulair®), zafirlukast (Accolade®), zileuton (Zyflo®)
    • i) Anti-inflammatory agents
    • (1) For prophyllaxis only – NOT A “RESCUE” drug
    • (a) Efficacy similar to cromolyn but more side effects
    • ii) MOA:
    • (1) Prevents leukotrienes form causing inflammation
    • iii) Side Effects & Cautions
    • (1) Headache
    • (2) GI upset
    • (3) Liver enzyme changes
    • (a) Inhibits P450 enzymes so decreases metabolism of many other drugs
    • c) Corticosteroids: Inhaled or Systemic
    • i) Used only if other therapy doesn’t control symptoms
    • ii) Positive interaction of inhaled corticosteroids and long acting sympathomimetics
    • iii) Corticosteroid available as aerosol, talbets, and injections
    • iv) Note: when these medications are needed, side effects of inhalers are much more acceptable than consequences of non-treatment
    • v) Therapeutic Uses
    • (1) Asthma & other severe COPD
    • (2) Status asthmaticus (associated w/ bronchospasms)
    • vi) MOA:
    • (1) Suppression of antibody formation (including IgE responsible for allergy attacks)
    • (2) Increases cyclic AMP which is needed for bronchodilation
    • (3) Decreases cyclic GMP which causes bronchoconstriction
    • vii) Side Effects
    • (1) Local (w/ inhaler use)
    • (a) Hoarseness, dry mouth, local infections in mouth and pharynx
    • (2) Systemic (minimized by inhaler)
    • (a) Irreversible
    • (i) Osteoporosis (Ca++, protein, vitamin D helps), cataracts, stunting of growth in children
    • (b) Reversible
    • (i) Proneness to infections. Poor wound healing (including proneness to ulcers) (vitamin C helps), salt and water retention, signs of CNS stimulation (restlessness, insomnia, even manic states including depressive episodes in some individuals)
    • viii) Cautions:
    • (1) Rebound: Drug must be withdrawn slowly – body has decreased capacity to produce its own glucocorticoids. (Also must gradually switch to inhaler from oral forms of medication)
    • (2) During times of stress, patient may need extra glucocorticoid
    • (3) Full effect of steroid therapy may take 2-4 weeks to be seen
    • ix) Warning: Corticosteroid inhaler is not for treatment of acute attacks (not to be confused w/ catecholamine inhaler)
  3. 3) Goal of treatment for Asthma? What are the rescue drugs vs. drugs for chronic therapy?
    • a) Goal:
    • i) Anti-inflammation
    • ii) Bronchodilators
    • b) Rescue drugs
    • i) Sympathomimetics
    • ii) Xanthines
    • c) Drugs for chronic use
    • i) Asthma prophylactic – cromolyn
    • ii) Leukotriene Receptor Antagonist
    • iii) Corticosteroids
  4. 4) Anti-tussives- Narcotic vs Non-narcotic
    • a) Narcotic Antitussives – (Codeine, etc)
    • i) MOA:
    • (1) Depresses cough center in medulla of central nervous system
    • ii) Side Effects & Cautions:
    • (1) Potential for abuse limits usefulness of narcotic antitussives
    • (2) Constipation
    • (3) Depress respiration
    • (4) Cause drug dependency
    • b) Nonnarcotic Antitussives – (Usually fewer GI symptoms)
    • i) MOA:
    • (1) Some are peripherally acting
    • (a) Ex: benzonatate (Tessalon®) –reduces activity of lung stretch receptors, or benzocaine, a topical anesthetic whose usefulness has not been established
    • (2) Many act centrally as do the narcotics
    • (a) Do not have narcotic side effects
    • (b) Dextromethorphan- half as potent as codeine, no prescription necessary = an isomer of codeine that has no analgesic or addictive properties
    • ii) Side Effects & Cautions
    • (1) Skip- not serious- sometimes have atropine-like side effects, i.e. dry mouth, nausea and vomiting, etc
  5. 5) When do you treat a cough with an anti-tussive and when don’t you treat with an anti-tussive?
    • a) Therapeutic Uses
    • i) Preventing coughing
    • (1) Only when cough is nonproductive, exhausting, or very painful
    • b) Cautions:
    • i) COPD
    • (1) Asthma
    • (2) Chronic bronchitis
    • (3) Bronchiectasis
    • (4) Cystic fibrosis (congenital disease w/ dysfunction of exocrine glands
    • (a) In lung, overproduction of viscid mucus)
    • c) Use of antitussive is 2ndary to treatment of source of cough
    • i) Ex: in some asthmatics, cough is primary symptom
    • (1) –would use bronchodilation, before an antitussive
  6. 6) What is an expectorant, a demulcent
    • a) Demulcents
    • i) –agents w/ a soothing effect (gargles, lozenges, syrups, even steam treatment)
    • ii) Therapeutic Uses:
    • (1) For cough & throat irritation
    • iii) MOA:
    • (1) Protects respiratory lining from irritation & contact w/ air
    • iv) Cautions- none
    • b) Expectorant
    • i) –increase secretion of mucus I bronchi or modify it of reduce viscosity
    • ii) 1st Treatment:
    • (1) Steam & drink plenty of fluid (2 cups/hour)
    • iii) Therapeutic Uses:
    • (1) Asthma or other COPD (viscous mucus is the obstruction)
    • (2) Bronchitis
    • (3) Pneumonia
    • (4) Coughs
    • iv) MOA:
    • (1) Make secreation more fluid so can be moved (i.e. makes coughing more productive)
    • v) Side Effects
    • (1) Usually specific to drug used – we won’t discuss
  7. 7) Nasal decongestants- what are the 3 types?
    • a) Adrenergic agents
    • i) Better than antihistamines for colds, useful for allergy stuffiness too
    • ii) MOA: nasal vasoconstriction
    • iii) Caution: habituation occurs (rebound)
    • b) Antihistaminics
    • i) Ok for allergy, may help relieve cold symptoms
    • ii) (vs inflammation)
    • c) Intranasal Steroids – for allergy (- immune system= - swell= -congestion)
    • i) May increase risk of thrush & prevent healing of damage nasal mucosa
  8. 8) Histamine antagonizing drugs- what are they? What are the uses?
    • a) Histamine:
    • i) H1 receptors
    • (1) Contraction of bronchial & intestinal smooth muscle
    • (2) Dilation of arterioles & capillaries and increase permeability
    • ii) H2 receptors
    • (1) Increase gastric acid secretion
    • b) General approaches to therapy
    • i) Produce opposite effects as histamine (epinephrine)
    • (1) Good for counteracting symptoms of reaction that has occurred
    • (a) Only minor effect on histamine
    • ii) Prevent histamine reaction = “antihistamine”
    • (1) Histamine antagonist is a better term
    • (2) Compete w/ histamine for H1 & H2 receptor sites
    • (3) Most antihistaminics are H1 antagonists
  9. 9) Uses for H1 vs H2 antagonizing drugs
    • a) H1 Antagonists “Antihistamines” – (these are the classical “antihistamine”
    • i) 1st Generation types bind both centrally (CNS effects) & peripherally
    • (1) More sedating but also more useful as sedative, for motion sickness, or in special cases for treating Parkinson’s
    • (2) Ex: chlorpheniramine (Chlortrimeton®), clemastine (Tavist-D®), promethazine (Phenergan®)
    • ii) 2nd Generation types
    • (1) Less drowsiness
    • (2) These newer agents can produce adverse cardiovascular effects (hypo- or hyper-tension, syncope, tachycardia)
    • (3) Ex: azelstine (Asteline®), cetirizine (Zyrtec®), fexofenadine (Allegra®), and loratadine (Claritin®)
    • iii) Therapeutic Uses
    • (1) Antagonize allergic reactions (hives, watery eyes, stuffy nose – but NOT asthma!)
    • (a) Prevent more symptoms from occurring
    • (b) Less effective than epinephrine at counteracting reaction that has already occurred
    • (i) Mechanism:
    • 1. Besides preventing action of histamine, acts as mild sedative so more able to ignore distressing symptoms
    • (2) Motion sickness
    • (a) Not very effective at controlling nausea of other origins
    • (i) –meclizine (Antivert®)
    • 1. Mechanism:
    • a. Appear to depress CNS & decrease sensitivity of inner ear
    • iv) Side Effects: Chemical similarity to some antipsychotics & to atropine
    • (1) Antipsychotic-like: drowsiness, sedation, dizziness
    • (a) In others may cause agitation and hallucinations
    • (b) Higher therapeutic doses are usually sedating
    • (2) Antimuscarinic (atropine-like): dryness of mouth, blurred vision
    • v) Cautions:
    • (1) Potentiate other sedative-hypnotics, tranquilizers, and alcohol
    • (2) Avoid use in asthmatics (drying of bronchiole secretions)
    • (a) Asthma prophylactic cromolyn prevents the release of histamine by blocking degranulation of mast cells
    • (b) A similar agent lodoxamide is marketed in eye solutions for eye allergies
    • (c) Neither agent is an antihistaminic that competes for H1 receptor sites
    • (3) Do periodic blood tests (check for blood dyscarsias)
    • b) H2 Antagonist
    • i) Block a 2nd type of histamine receptors:
    • (1) Cimetidine (Tagamet®), famotidine (Pepcid®), nizatidine (Axid®), rantidine (Zantac®)
    • ii) These agents are not antihistamines as we know them
    • iii) Therapeutic Uses:
    • (1) Decrease gastric secretion (ulcer patients)
    • (2) Treat heartburn (esophageal reflux) – unapproved use
    • (a) Preliminary studies look promising for this use
    • iv) Side Effects:
    • (1) Minimal
    • (a) Doesn’t cause usual sedation in most patients
    • (b) Occasionally, causes diarrhea, muscle pain, rash, dizziness
    • (c) Also, because inhibits P450 enzymes, can delay metabolism of other drugs in liver
    • (2) Very rare
    • (a) Breast enlargement in some men
    • (b) Mental confusion in older patients
    • 10) Main differences between drugs used to stop a reaction from progressing and relieving symptoms from histamine that has already been released
    • a)
  10. 11) Why use an antacid
    • a) Therapeutic Uses:
    • i) Peptic ulcer
    • ii) Heartburn (may increase tone of lower esophageal sphincter)
    • b) Kinds
    • i) Systemic antacids
    • ii) Nonsystemic antacids
    • iii) Sedative or Antisecretory Agents
    • iv) Increase gastric emptying
    • c) Systemic Antacids (Sodium bicarbonate)
    • i) Not commonly prescribed by physician because may cause systemic alkalosis & electrolyte imbalance
    • ii) Side Effect: kidney must then adjust for imbalance
    • (1) Note: Found in effervescent products such as Alka Seltzer® and instant Metamucil®
    • (2) CO2 gas and electrolyte imbalances may stimulate more aid production
    • d) Nonsystemic Antacids
    • i) Mechanisms:
    • (1) Form insoluble products so not absorbed
    • (2) Neutralize hydrogen ion
    • ii) Ex:
    • (1) Aluminum compounds (Rolaids®) and calcium compounds (Tums®)
    • (a) Calcium may actually stimulate more acid production later (ie.e excessive milk drinking not a good idea).
    • (2) Magnesium compounds (Milk of Magnesia)
    • iii) Side Effects: - not serious
    • (1) Al or Ca = constipation
    • (2) Mg = diarrhea
    • (a) Combo of 2 types help avoid problem
    • (b) Al have slower onset; Mg more quickly = good combo
    • iv) Caution:
    • (1) Antacids alter absorption of many drugs
    • (2) Particularly important if kidney/liver disease
    • e) Sedative/Antisecretory Agents: Inhibit secretion by different mechanisms
    • i) H2 antagonists – inhibit gastric secretion
    • (1) Ex: Cimetidine (Tagamet®)
    • ii) Anticholinergic drugs (ex: Donnatal®)
    • iii) Prostaglandins – misoprostol (Cystotec®)
    • (1) Reduces acid, increases mucus secretion
    • (2) Contraindicated in pregnancy (miscarriages has occurred)
    • iv) Proton Pump Inhibitors
    • (1) Short term use (4-8 weeks)
    • (2) Directly diffuses into gastric epithelium ot suppress acid secretion
    • f) Increase Gastric Emptying (Drugs): Seems to increase sensitivity to acetylcholine
    • i) Ex: cisapride (Propulsid®), metoclopramide (Reglan®)
    • ii) Relaxes pylorus & stimulates motility
    • iii) Relieves heartburn & nausea caused by gaseous distention
    • g) About Ulcers:
    • i) Older ulcer treatments focus on antacids
    • (1) Best after each meal & bedtime
    • (2) Not as effective as H2 antagonists, but not as much rebound ulceration
    • ii) Note: Sucralfate (Carafate®), aluminum hydroxide & sulfate sucrose
    • (1) Minimal antacid effect
    • (2) Adheres to ulcerated region (protect it) & decrease pepsin activity
    • (3) Sucralfate is as effective as H2 antagonist at healing
    • (a) Its best used before meal & before antacids because needs some acid to become active
  11. 12) What is a digestant, emetic, antiemetic, cathartic, antidiarrheics? When to use and when not to use.
    • a) Digestants
    • i) Most no longer considered effective
    • (1) Includes acids & enzymes
    • ii) Exception
    • (1) Pancreatic enzymes are still considered useful
    • b) Emetics
    • i) Cause vomiting – (apomorphine, ipecac)
    • ii) Therapeutic Uses – poisoning
    • iii) Caution:
    • (1) w/ some poisons, vomiting is contraindicated:
    • (a) convulsant drug
    • (b) oil based substances
    • (c) corrosive substances
    • c) Antiemetic: Note: vomiting reflex stimulated by GI & CNS irritation
    • i) Local antiemetic
    • (1) Releiaves irriation
    • (a) Antacis
    • (b) Carminatives (relieve gas)
    • ii) Systemic antiemetics
    • (1) Depress vomiting center in medulla
    • (a) Phenothiazines – among more effective
    • (b) Antihistamines – if cause is motion sickness
    • (i) Use prior to onset of symptoms
    • (c) Tetrahydrocannabinol (THC)
    • (i) Active ingredient in marijuana
    • (ii) Often useful if nausea due to chemotherapy
    • (iii) Main antiemetic value in patiens who don’t respond to other antiemetics such as prochlorperazine (Compazine®)
    • (iv) Side effects
    • 1. Drowsiness
    • 2. Dry mouth, tachycardia
    • 3. Dizziness, inability to concentrate, disorientation
    • 4. Anxiety, depression, paranoia, manic psychosis, visual hallucinations
    • (d) Metoclopramide (Reglan ®) – relaxes pylorus & stimulates motility
    • (i) Relieves heartburn & nausea caused by gaseous distention
    • d) Cathartics (means to cleanse)
    • i) Contrast w/ laxatives or purgatives
    • ii) Major causes of constipation include
    • (1) Lack of diet fiber
    • (2) Lack of exercise
    • (3) Drugs, overuse of cathartics
    • (4) Lack of peristalsis (many causes)
    • iii) Therapeutic Uses
    • (1) Treat or avoid constipation – some significant ex:
    • (a) Bedridden patients
    • (b) Patients w/ hemorrhoids
    • (c) Patients w/ cardiovascular disease
    • (2) Surgery or diagnostic procedures
    • (3) Worms infestation
    • (a) Used in conjunction w/ poison for worm
    • (4) Chemical poisoning
    • (a) When chemical has gotten past stomach
    • iv) Contraindications:
    • (1) Undiagnosed abdominal pain
    • (a) Appendicitis (may lead to rupture)
    • (b) Inflammatory disease of GI tract (too irritating)
    • (2) GI obstruction including fecal impaction
    • (3) Later stages of pregnancy
    • v) MOA:
    • (1) Irritant (acts as stimulant to peristalsis)
    • (a) Caster oil, phenolphthalein
    • (2) Bulk-forming (colloids like agar & methlcellulose that attract water)
    • (a) Some brand names: Metamucil®, Cologel®, Mitrolan®
    • (b) Lactulose (Chronulac®) acts as an osmotic agent and as an irritant
    • (c) Natural sources: fruits & vegetables
    • (d) Special notes: these same drugs may be used to treat diarrhea
    • (3) Saline cathartics
    • (a) Ex: Milk of Magnesia & other magnesium salts
    • (b) Hypertonic saline that attracts water to feces caution if renal impairment
    • (c) Uses: Treat edema; Secure stool specimens for worms; Some poisonings
    • (4) Lubricants & fecal moistening agents – (both act to keep feces soft)
    • (a) Hemorrhoid surgery, myocardial infarctions, aneurysms, cerebrovascular disorders
    • (b) Ex: mineral oil, glycerin suppositories, sodium docusate
    • (c) Oils may inhibit absorption of fat soluble nutrients (take on empty stomach)
    • e) Antidiarrheics
    • i) Important problem: diarrhea can cause
    • (1) Dehydration
    • (2) Exhaustion
    • (3) Electrolytes & acid-base imbalance
    • ii) Note: Treatment of chronic diarrhea should be aimed at the problem
    • (1) Laxative abuse
    • (2) Lactose intolerance
    • (3) Irritable bowel syndrome, Crohn’s disease, etc.
    • iii) MOA:
    • (1) Demulcents and protective
    • (a) Help prevent irrigation (limited usefulness)
    • (2) Absorbents – absorb gas or irritating substance
    • (a) Bismuth subsalicylate, Kaopectate®, activated charcoal
    • (3) Astringents – precipitate protein & cover surface of membrane
    • (a) Prevents further irritation, shrinks tissue
    • (4) Antiinfectives – if caused by microorganisms
    • (a) Note: do not inhibit peristalsis if microorganism present
    • (5) Sedatives & antispasmodics – opium preparation & antimuscarinic
    • (a) Ex: Imodium®, Lomotil®, paregoric are combinations of a narcotic and an antimuscarininc drug
    • (6) Lactobacillus – normalizes intestinal flora
    • (a) Especially good if diarrhea follows antibiotic therapy
    • f) Carminatives/antiflatulents
    • i) + motility to help expel gas
    • ii) Simethicone is an antifoaming agent
    • iii) Charcoal capsules for intestinal gas
    • (1) As much as one gram before & after meals
    • (2) Caution: absorbs oral medications

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