RESPIRATORY DRUGS

CHAPTER 6

ANTITUSSIVES

-The cough reflex occurs when receptors in the airway send impulses to the brainstem and cause contraction of the muscles needed to cough.

-The type of cough produced depends on the location of the stimulated receptors and whether or not mucus is brought up with the cough (productive or non productive).

Butorphanol

Hydrocodone

Codeine

Dextromethorphan

ANTITUSSIVES

• Antitussives act centrally by suppressing the neurons located in the brainstem’s cough center.

• Antitussives should be used with caution since coughing is a protective mechanism. Animals with very productive coughs or coughs with very sticky mucus should be allowed to occur as the body may be relying on the cough to prevent the airway from being obstructed by mucus.

• Antitussives are often used with tracheitis, tracheobronchitis. When coughing worsens the inflammation that is already present and stimulates more coughing, it needs to be suppressed.

Butorphanol *Torbutrol, *Torbugesic

• Opioid cough suppressant (Class IV) that is also commonly used for pain control.

• Won’t cause as much respiratory or cardiovascular suppression as hydrocodone or codeine and also causes less sedation.

Hydrocodone *Hycodan

• Opioid cough suppressant in Class II

• Strong antitussive, however sedation is often noted as well as constipation if used long-term

• Can also mask pain

Codeine

• Range from Class II to Class V, depending on if it is combined with any other drugs. Codeine alone is in Class II.

• Sedation, nausea, and constipation may be seen

Dextromethorphan• Not a controlled substance, no pain control.

• Most commonly used cough suppressant in people, found in OTC cough, flu, and cold medications. Often combined with other medications. Make sure it does not contain Tylenol if giving to cats!

• Not as effective as the other types of antitussives

MUCOLYTIC

AcetylcysteineAcetylcysteine

Acetylcysteine *Mucomyst

•If mucus is thick or sticky, the cilia may be unable to move it toward the mouth to be coughed up. •These agents break up mucus (by breaking disulfide bonds) and reduce its viscosity, making it easier to move.

•Med has an unpleasant taste so tablets are either flavored or the product is nebulized

EXPECTORANTS

Guafenesin, Ammonium chloride, Potassium iodide, Sodium citrate

Guafenesin, Ammonium chloride, Potassium iodide, Sodium citrate

• Liquefy mucus, reducing its adhesiveness

• Indicated when a productive cough is present.

• Also cause irritation of the gastric mucosa and stimulation of the parasympathetic nervous system- vomiting can be a side effect.

• Ideally should not be used with an antitussive, but the antitussive will not be able to completely suppress the cough caused by the increased secretions.

DECONGESTANTS

Pseudoephedrine, ephedrine, phenylephrine

Pseudoephedrine, ephedrine, phenylephrine

• Reduce vascular engorgement of swollen nasal tissues

• Stimulate alpha one receptors to vasoconstrict vessels leading to skin and mucous membranes. When the engorged vessels are constricted, edema and mucous secretions are reduced.

• Stimulation of Beta one receptors is a side effect so increased heart rate may be seen. Use with caution in patients with cardiovascular disease.

BRONCHODILATORS

Albuterol, Terbutaline,

Epinephrine

Atropine, Glycopyrrolate

Atropine, Glycopyrrolate

Diphenhydramine, Hydroxyzine,

Cyproheptadine, Cetirizine, Clemastine,

Loratadine, Fexofenadine

Theophylline, Aminophylline

Prednisone,

Dexamethasone

BRONCHODILATORS• Bronchoconstriction: the contraction of smooth muscles

surrounding the small terminal bronchioles.

• Can be caused by:

• Stimulation of the parasympathetic nervous system to release acetylcholine by drugs, insecticides, or toxicants. Similarly, drugs that inhibit acetylcholinesterase can have the same effect.

• Stimulation of H1 receptors- histamine receptors on smooth muscle cells

(seen in allergic reactions)

• Blocking Beta 2 receptors.

• Along with bronchoconstriction comes increased respiratory secretions, edema, and dyspnea.

Beta Adrenergic Agonists- Albuterol, Terbutaline, Epinephrine• Stimulate Beta receptors.

• Drugs that stimulate Beta two receptors are used as bronchodilators.

• If the drug also stimulates Beta one receptors, increased heart rate and contractility is expected.

• Newer meds target only Beta two receptors, epinephrine stimulates all Beta receptors.

• Can be given orally or by inhalation.

• Body cells can become less responsive to these drugs over time since downregulation of receptors occurs with prolonged exposure.

Anticholinergics- Anticholinergics- Atropine, Atropine, GlycopyrrolateGlycopyrrolate

•Combine with acetylcholine receptors to prevent acetylcholine from causing bronchoconstriction.

•Used with organophosphate/carbamate toxicity

Antihistamines- Diphenhydramine *Benadryl, Hydroxyzine *Atarax, Cyproheptadine *Periactin, Cetirizine *Zyrtec, Clemastine *Tavist, Loratadine *Claratin, Fexofenadine *Allegra)

• Histamine is released from mast cells during an allergic response. It combines with H1 receptors on bronchiole smooth muscles and causes bronchoconstriction.• Antihistamines prevent mast cell degranulation and block H1 receptors.

• More effective when given as a preventative as they don’t displace histamine that has already combined with receptors.

• Most have the suffix “-ine”.

Methylxanthines- Theophylline, Aminophylline

• Caffeine is also in this family of drugs• Interfere with calcium mobilization that is needed for actin and

myosin to cause contractions that constrict the airways.

• Narrow therapeutic index• Theophylline competes with many drugs for liver metabolism. • 100 mg of Aminophylline contains 80 mg of theophylline. Dosages

differ between aminophylline and pure theophylline.

Glucocorticoids- Prednisone, Dexamethasone

• So important that they get their own chapter…. Stay tuned