Transcript Drugs Affecting Respiratory System

Drugs Affecting Respiratory
System
Antihistamines
Drugs that directly compete with histamine
for specific receptor sites
• Two histamine receptors
– H1 (histamine1)
– H2 (histamine2)
• Histamine-mediated disorders
– Allergic rhinitis (hay fever, mould and
dust allergies)
– Anaphylaxis
– Drug fevers
– Insect bite reactions
– Urticaria (itching)
H1 antagonists are commonly referred to as
antihistamines
•
Antihistamines have several properties
– Antihistaminic
– Anticholinergic
– Sedative
Mechanism of Action
• Block action of histamine at the H1
receptor sites
• Compete with histamine for binding at
unoccupied receptors
• Cannot push histamine off the receptor if
already bound
• The binding of H1 blockers to the
histamine receptors prevents the adverse
consequences of histamine stimulation
• Prevent smooth muscle contraction of the
bronchial airways
• Decrease mucus secretion
• Prevent increase of vascular permeability
• More effective in preventing the actions of
histamine rather than reversing them
• Should be given early in treatment, before
all the histamine binds to the receptors
Indications
• Nasal allergies
• Seasonal allergic rhinitis
(hay fever)
• Allergic reactions
• Motion sickness
• Sleep disorders
• Also used to relieve symptoms associated
with the common cold such as sneezing,
runny nose (Palliative treatment, not
curative)
Side Effects
• Anticholinergic effects, most common
– Dry mouth
– Difficulty urinating
– Constipation
– Changes in vision
• Drowsiness
– Mild drowsiness to deep sleep
First generation
– Diphenhydramine (Benedryl )
– Chlorpheniramine (Piriton)
– Promethazine hydrochloride
(Phenergan)
Second generation
• Loratidine
• Ceterizine/cetrizine
They are much less likely to have side
effects of sedation and dry mouth
• Use with caution in increased intraocular
pressure, cardiac or renal disease,
hypertension, asthma, COPD, peptic ulcer
disease
Decongestants
What is nasal congestion?
• Excessive nasal secretions
• Inflamed and swollen nasal mucosa
• Primary causes
– Allergies
– Upper respiratory infections (common
cold)
Two decongestant forms
• Oral/systemic
• Inhaled/topically applied to the nasal
membranes
Topical Nasal
Decongestants
• Adrenergics
• Intranasal steroids
Mechanism of Action
•
Adrenergics
– Constrict small blood vessels that
supply Upper Respiratory Tract
structures
– As a result these tissues shrink, and
nasal secretions in the swollen mucous
membranes are better able to drain
– Nasal stuffiness is relieved
•
Nasal steroids
– Anti-inflammatory effect
– Work to turn off the immune system
cells involved in the inflammatory
response
– Decreased inflammation results in
decreased congestion
– Nasal stuffiness is relieved
• Adrenergics
– Ephedrine hydrochloride
• Intranasal steroids
– Beclomethasone dipropionate
Side Effects
Adrenergics
Steroids
Nervousness
Local mucosal dryness
Insomnia
and irritation
Palpitations
Tremors
(systemic effects due to
adrenergic stimulation of the
heart, blood vessels, and CNS)
Oral decongestants
• Not that effective
• Have unwanted sympathomymetic effects
• Pseudoephridine
Antitussives
• Drugs used to stop or reduce coughing
• What is cough? Respiratory secretions and
foreign objects are naturally removed by the
Cough reflex initiated by irritation of sensory
receptors in the respiratory tract
• Productive cough
– Congested, removes excessive secretions
• Nonproductive cough
– Dry cough
Opioids
• Suppress the cough reflex by direct action
on the cough centre in the medulla
Examples:
– Codeine
– Hydrocodone
Nonopioids
• Suppress the cough reflex by numbing the
stretch receptors in the respiratory tract
and preventing the cough reflex from
being stimulated
Examples:
– Dextromethorphan
Indications
• Used to stop the cough reflex when the
cough is nonproductive and/or harmful
Expectorants
• Drugs that aid in the expulsion
(removal) of mucus/ bronchial secretions
• Reduce the viscosity of secretions
• Disintegrate and thin secretions
• By loosening and thinning sputum and
bronchial secretions, the tendency to
cough is indirectly diminished
• Used for the relief of nonproductive
coughs
What happens in ASTHMA ?
•Asthma causes a narrowing of the
breathing airways
• The narrowing that occurs in asthma is
caused by three major factors:
inflammation, bronchospasm, and
hyperreactivity.
• In inflammation the bronchial tubes
become red, irritated, and swollen
• The muscles around the bronchial tubes
tighten during an attack of asthma. This
muscle constriction of the airways is called
bronchospasm
• In patients with asthma, the chronically
inflamed and constricted airways become
highly sensitive, or reactive, to triggers
such as allergens, irritants, and infections.
• Exposure to these triggers may result in
progressively more inflammation and
narrowing and this is called hyperreactivity
• The combination of these three factors
results in difficulty with breathing out, or
exhaling.
• As a result, the air needs to be forcefully
exhaled to overcome the narrowing,
thereby causing the typical "wheezing"
sound.
• People with asthma also frequently
"cough" in an attempt to expel the thick
mucus plugs.
• Reducing the flow of air may result in less
oxygen passing into the bloodstream, and
if very severe, carbon dioxide may
dangerously accumulate in the blood
Management of asthma
• some drugs are given to treat acute
asthma exacerbations
• Some drugs are used as long term
maintenance therapy
Bronchodilators
Bronchodilators
•
•
•
•
Adrenoceptor agonists
Antimuscarinic bronchodilators
Xanthene derivatives –theophilline
Antileukotriene agents/Leukotriene
receptor antagonists
• Cromones
Adrenoceptor agonists
• Used during acute phase of asthmatic
attacks
• Quickly reduce airway constriction and
restore normal airflow
• Stimulate beta2-adrenergic receptors
throughout the lungs
• Selective beta2 drugs
– Stimulate only beta2-receptors
– Commonly used
– Example: salbutamol
Selective beta2 agonists
•
•
•
•
Salbutamol
Terbutaline
Salmeterol
Formeterol
Side Effects
•
•
•
•
Tremor
Headache
Peripheral venous dilatation
Palpitations
• Contraindicated: clients with severe
cardiac disease
Antimuscarinic bronchodilators/
Anticholinergics
• Acetylcholine (ACh) causes bronchial
constriction and narrowing of the airways
• Anticholinergics bind to the ACh receptors,
preventing ACh from binding
• Ex-ipratropium bromide
• Side effects: dry mouth, nausea,
constipation, headache
Antileukotriene agents/Leukotriene
receptor antagonists
• Montelukast
• Zafirlukast
Mechanism of Action
• Leukotrienes are substances released
when expose to a trigger, such as cat hair
or dust, and starts a series of chemical
reactions in the body
• Leukotrienes cause inflammation,
bronchoconstriction, and mucus
production
• Result: coughing, wheezing, shortness
of breath
• Antileukotriene agents prevent
leukotrienes from attaching to receptors on
cells in the lungs and in circulation
• Inflammation in the lungs is blocked, and
asthma symptoms are relieved
Mast cell stablizers
Sodium cromoglicate
• Mechanism of action is not very clear, but
known to affect on inflammatory mediated
cells
• Indicated in prophylaxis of asthma by
inhalation
Preventers
Corticosteroids
• Very effective in asthma
• Mechanism of action :
- Enter cells where they combine with
steroid receptors in cytoplasm
- Inhibit inflammation/reduce synthesis of
inflammatory mediators
Inhalers
IN asthmatics inhalers are used to deliver
drugs more effectively with minimal side
effects
Relievers have to be taken when they get
worsening of asthma
Preventers should be used daily for it to be
effective
Patients should be clearly educated on this
…
Oxygen Therapy
• Oxygen therapy is the administration of
oxygen as a medical intervention
• Administration of oxygen at concentrations
greater than that in room air ( 21%) to treat
or prevent hypoxemia (not enough oxygen
in the blood)
High concentration O2 therapy
• Concentrations up to 60%
• Use in pneumonia and many other
conditions
Low concentration O2 therapy
• The concentration should not exceed 28%
• Used in COPD
• Improve the hypoxemia with out worsening
existing CO2 retention
• Oxygen can deliver to the respiratory
system via nasal canula, tracheostomy
and face mask