DRUGS ACTING ON THE
RESPIRATORY SYSTEM
RESPIRATORY SYSTEM
... is the biological system of an organism that introduces respiratory gases to the interior and performs gas exchange
THE PATHWAY:
- Air enters the nostrils
- passes through the nasopharynx,
- the oral pharynx
- through the glottis
- into the trachea
- into the right and left bronchi, which branches and rebranches into
- bronchioles, each of which terminates in a cluster of
- alveoli
**Only in the alveoli does actual gas exchange takes place. There are some 300 million alveoli in two adult lungs. These provide a surface area of some 160 m2 (almost equal to the singles area of a tennis court and 80 times the area of our skin!).
BREATHING
In mammals, the diaphragm divides the body cavity into the
Because of this adhesion, any action that increases the volume of the thoracic cavity causes the lungs to expand, drawing air into them.
At the same time, some of the carbon dioxide in the blood diffuses into the alveoli from which it can be exhaled.
**DRUGS ACTING ON THE RESPIRATORY SYSTEM
A. ANTITUSSIVES
Prototype: Dextromethorphan
...suppress cough reflex; indicated for UNPRODUCTIVE COUGH
...substance controlled drug; administration every 4hours
...acts on the center of the brain; NOT a drug of choice for brain injury due to CNS depression
...CAUTIOUSLY used in patients with history of drug addiction, patients who are driving because of its potential side effects like drowsiness and sedation
...CONTRAINDICATED in patients who need to cough to maintain the airways like post-operative patients because it could lead to accumulation of secretions
Common Adverse Effects
constipation vomiting
dizziness nausea
painful urination increased sensitivity to sunlight
drowsiness restlessness
lightheadedness nervousness
nightmares unusual tiredness
*they only affect a small amount of users.
Severe Side Effects
anxiety physical dependence
fear mental and physical impairment
mood changes uretheral spasms
skin rash respiratory depression
*These side effects are also very rare and do not affect a large number of users.
B. DECONGESTANTS
...drugs that decrease blood flow to the upper respiratory tract and decrease the overproduction of secretions
Oral: Pseudoephedrine (Decofed)
...for nasal congestion caused by common cold, allergic rhinitis, relief of pain and congestion of otitis media
Steroid Decongestant
... are currently very popular for the treatment of allergic rhinitis in patients who are no longer getting any response with other decongestants
When decongestants are used in the form of nose drops or nasal spray, the following adverse effects are common:
C. ANTIHISTAMINE
...bring relief to allergies, itchy eyes, nasal swelling, congestion
...use CAUTIOUSLY in patients with arrythmias
1st Generation ... Benadryl: 25-50mg PO
: for rhinitis; sleeping aids, urticaria
2nd Generation ... have fever effects; non-sedating
... Claritin: relief of allergic rhinitis, urticaria
: adjunct treatment for anaphylactic reaction
Adverse Effects: dry mouth
Responsibilities: let patient suck sugarless lozenges, ice chips
: limit fluid intake to decrease swelling and use of humidifier
D. EXPECTORANTS
... drugs that liquefy secretions, making it easier for the patient to cough them
Prototype: Guaifenesin (Solmux, Mucinex)
: for dry cough, influenza, acute bronchitis (massive production of secretion lasting 3 months)
: relief of productive cough; should not be used for more than a week
E. MUCOLYTICS
... work by breaking down mucus in order to aid thick, and tenacious cough
Prototype: Acetylcysteine (Ventolin)
: 2-20ml every 6 hours (by nebulization)
Adverse Effects: accompanies frequent or prolonged use of decongestants is REBOUND VASODILATION or RHINITIS MEDICAMENTOSA (which occurs when the nasal passages become congested as the drug effect wears off, thus, the patient tend to use more drug to decrease the congestion that leads to abuse of the decongestant)
F> BRONCHODILATORS
...a.k.a. Antiasthmatics
... used to facilitate respirations by dilating the airways
... helpful in prevention of bronchial asthma associated with COPD
BREATHING
In mammals, the diaphragm divides the body cavity into the
- abdominal cavity, which contains the viscera (e.g., stomach and intestines) and the
- thoracic cavity, which contains the heart and lungs.
Because of this adhesion, any action that increases the volume of the thoracic cavity causes the lungs to expand, drawing air into them.
- During inspiration (inhaling),
- The external intercostal muscles contract, lifting the ribs up and out.
- The diaphragm contracts, drawing it down .
- During expiration (exhaling), these processes are reversed and the natural elasticity of the lungs returns them to their normal volume. At rest, we breath 15–18 times a minute exchanging about 500 ml of air.
- In more vigorous expiration,
- The internal intercostal muscles draw the ribs down and inward
- The wall of the abdomen contracts pushing the stomach and liver upward.
At the same time, some of the carbon dioxide in the blood diffuses into the alveoli from which it can be exhaled.
**DRUGS ACTING ON THE RESPIRATORY SYSTEM
A. ANTITUSSIVES
Prototype: Dextromethorphan
...suppress cough reflex; indicated for UNPRODUCTIVE COUGH
...substance controlled drug; administration every 4hours
...acts on the center of the brain; NOT a drug of choice for brain injury due to CNS depression
...CAUTIOUSLY used in patients with history of drug addiction, patients who are driving because of its potential side effects like drowsiness and sedation
...CONTRAINDICATED in patients who need to cough to maintain the airways like post-operative patients because it could lead to accumulation of secretions
Common Adverse Effects
constipation vomiting
dizziness nausea
painful urination increased sensitivity to sunlight
drowsiness restlessness
lightheadedness nervousness
nightmares unusual tiredness
*they only affect a small amount of users.
Severe Side Effects
anxiety physical dependence
fear mental and physical impairment
mood changes uretheral spasms
skin rash respiratory depression
*These side effects are also very rare and do not affect a large number of users.
B. DECONGESTANTS
...drugs that decrease blood flow to the upper respiratory tract and decrease the overproduction of secretions
Oral: Pseudoephedrine (Decofed)
...for nasal congestion caused by common cold, allergic rhinitis, relief of pain and congestion of otitis media
Steroid Decongestant
... are currently very popular for the treatment of allergic rhinitis in patients who are no longer getting any response with other decongestants
When decongestants are used in the form of nose drops or nasal spray, the following adverse effects are common:
- stinging
- burning
- sneezing
- increased nasal discharge
- altered sense of taste
- restlessness
- anxiety
- nervousness
- weakness
- difficulty breathing
C. ANTIHISTAMINE
...bring relief to allergies, itchy eyes, nasal swelling, congestion
...use CAUTIOUSLY in patients with arrythmias
1st Generation ... Benadryl: 25-50mg PO
: for rhinitis; sleeping aids, urticaria
2nd Generation ... have fever effects; non-sedating
... Claritin: relief of allergic rhinitis, urticaria
: adjunct treatment for anaphylactic reaction
Adverse Effects: dry mouth
Responsibilities: let patient suck sugarless lozenges, ice chips
: limit fluid intake to decrease swelling and use of humidifier
D. EXPECTORANTS
... drugs that liquefy secretions, making it easier for the patient to cough them
Prototype: Guaifenesin (Solmux, Mucinex)
: for dry cough, influenza, acute bronchitis (massive production of secretion lasting 3 months)
: relief of productive cough; should not be used for more than a week
E. MUCOLYTICS
... work by breaking down mucus in order to aid thick, and tenacious cough
Prototype: Acetylcysteine (Ventolin)
: 2-20ml every 6 hours (by nebulization)
Adverse Effects: accompanies frequent or prolonged use of decongestants is REBOUND VASODILATION or RHINITIS MEDICAMENTOSA (which occurs when the nasal passages become congested as the drug effect wears off, thus, the patient tend to use more drug to decrease the congestion that leads to abuse of the decongestant)
F> BRONCHODILATORS
...a.k.a. Antiasthmatics
... used to facilitate respirations by dilating the airways
... helpful in prevention of bronchial asthma associated with COPD