anti asthmatics
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Anti-Asthmatic Agents
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Contents:Definitions
MechanismPathology
Classification
Agents in detail
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ASTHMA:
It is physiologically characterized by
increased responsiveness of trachea and
bronchi to various stimuli and by wide spread
narrowing of the airways.
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FACTORS INFLUENCING ASTHMA
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The mechanisms underlying bronchial hyperactivity are
somehow related to inflammation of airway mucosa.
The agents that increase bronchial reactivity, such as
ozone exposure, allergen inhalation, and infection with
respiratory viruses, also cause airway inflammation.
MECHANISM
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PATHOLOGY
Its pathologic characters are contraction of airway
smooth muscle, mucosal thickening from edema and
cellular infiltration, and inspissations in the airwaylumen of abnormally thick, viscoid plugs of mucus.
The products of cells in the airways, such as eosinophil,
lymphocytes, macrophages, mast cells, sensory nerves,and epithelial cells, have been shown to alter airway
smooth muscle function.
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Asthma relievers-classification:
2 categories
Short term relievers:
b-adrenoceptorstimulants
Theophylline
Anti-muscuranic agents
Long term relievers:
Anti-inflamatory agents
Inhibitors of mast cell
degranulation
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b- adrenoceptor agonists are of
Non-selective agents
Adrenaline/epinephrine
Ephedrine
Isoproterenol
Selective agents
Salbutamol
Terbutaline
clenbuterol
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.Adrenoceptor agonists:
//mechanism
1. Stimulation of 2 receptor in bronchial
smooth muscle cell membrane cAMP Ca2+smooth musle relaxation .
2. Also activate receptor on mast cell mb. ,
thus used in prophylaxis of allergicasthma .
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3. Stimulation of receptor in bronchial vessels
contraction of vascular smooth muscle edema .
4. The density of receptor will decrease after
prolonged treatment.
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Adrenaline
/epinephrineAdrenaline
/epinephrine :
//agonist of and receptor
//adverse effect of cardiovascular system
usually occurs thereby less usable
//s.c.
Injection
EphedrineEphedrine
//orally administered
//similar action to Adrenaline//less usable for central excitation
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Isoproterenol//agonist of 1&2 receptor
//no action on receptor
//used for acute attack of bronchoasthma
by inspiration route//orally ineffective
//involved in adverse effect of 1 receptor
excitation.
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Selectively 2
receptor agonist
Salbutamol
Terbutaline
ClenbuterolClenbuterol
The 2-Selective adrenoceptor agonist drugs are the
most widely used sympathomimetics for the treatment
of asthma at the present time.
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//Mechanism :Air way smooth muscle has little
sympathetic nervous supply but contain lots of 2-
adrenoceptors that respond to circulating adrenaline.
The stimulation of 2-receptors leads to a rise
in intracellular cAMP levels and the subsequent
bronchial smooth muscle relaxation
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They are effective after inhaled or oral
administration and have a long duration of action
and significant 2 selectivity.
Given by inhalation , these agents cause
bronchodilation equivalent to that produced by
isoproterenol.
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22--adrenoceptoradrenoceptor agonistagonist maymay alsoalso helphelp toto preventprevent thetheactivationactivation ofof mastmast cellcell inin aa minorminor degreedegree ..
ModernModern selectiveselective 22--receptorreceptor agonistsagonists areare potentpotentbronchodilatorsbronchodilators andand havehave veryvery fewfew 11 --stimulatingstimulating
propertiesproperties..
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//Route of administrationRoute of administration :
usually delivered via a metered doseinhaler with immediate effect
orally used in children
iv used for acute-care.
S.C. (terbutaline)
//Adverse effectAdverse effect :
cardiac arrhythmias
tolerance to agonisthypoxemia
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They are divided into two types :
1. Salt complex :
Increased water solubility without augmentation of
pharmacological action , such as :
Aminophylline
Choline theophylline
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2. Agent of delayed release :
Small fluctuation of blood concentration after
oral administration thus used for nocturnal attact of
asthma protheo
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//Mechanism :
Anti-inflammation
inhibit activity of PDE cAMP Ca 2+
bronchial relaxation
increase the release of Noradrenaline,adrenaline
inhibition the cell surface receptor of adenosine
interfere with the transportation of Ca 2+
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//pharmacodynamics The bronchodilation is the major therapeutic action in
asthma.
Potent effects in improving contractility and in
reversing fatigue of diaphragm in patients with chronicobstructive lung diseases.
Direct positive chronotropic and inotropic effects on
the heart.
In large doses, these agents also relax vascular smooth
muscle.
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//Administration route : orally effectivebut different from adrenergic agent for
metabolism by P450 enzyme system
//Indications : Bronchial asthma (+receptor agonist)
Chronic obstructive lung diseases
Cardiogenic asthma
Sleep apnea syndrome
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//Adverse effect :
it has a narrow therapeutic window and its
therapeutic and toxic effects are related to its
plasma concentration.
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. Muscarinic antagonist :
Ipratropium bromide
Ipratropine
//Mechanism :act by blocking muscarinic receptors
esp. the M3
subtype , which responds
to this parasympathetic bronchial
constrictor tone .
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//Route of administration :metered dose inhaler
//Indication :
used as adjuncts to 2-adrenoceptoragonist in treatment of asthma and more
effective in vagus-induced asthma .
//Therapeutic note :synergism when administered with
2-adrenoceptor agonist.
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.Anti-inflammatory drug
Glucocorticoids include :
beclomethasone
budesonide
//Mechanism :
depress the inflammatory response in
bronchial mucosa thus diminish bronchial
hyperresponsiveness.
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Anti-inflammatory effect
Immunosuppressive effect
Increase the response to catecholamines
Adenoceptor-upregulation
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//Route of administration :
orally i.v
used for : severe asthma
status asthmaticus
metered dose inhaler
//Indications :
Because of the efficacy and safety of inhaled
corticosteroids, they are now routinely prescribed forpatients who require more than occasional inhalations of
agonist for relief of symptom.
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// Adverse effect: Oropharyngeal candidacies
it can be reduced by having patients gargle water
and spit after each inhaledtreatment.
Hoarseness(roughness)
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.Anti-allergic agents
i.e. mast-cell-stabilizers
cromolyn sodium
//Mechanism :
They appear to stabilize antigen-sensitized mast cell by
reducing calcium influx and subsequent release of
inflammatory mediators .
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On mast cells, for inhibition of the early response
to antigen challenge
On eosinophils, for inhibition of the inflammatoryresponse to inhalation of allergens
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//Route of administration :
metered dose inhaler of cromoly sodium
//Indications :
pretreatment with cromolyn blocks the
bronchoconstriction caused by antigen
inhalation ,by exercise, by aspirin, and by
a variety of cause of occupational asthma.
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// Adverse effect
Throat irritation
Cough
Mouth dryness
Chest tightness and so forth
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REFERENCES
LIPPINCOTT.
TRIPATHI.
WWW.pharmacology.com/phaame.htm
Mediconet.blogspot.com/2009/08/interactive_clinical pharmacology.
Wps.prenhall.com/chet_turley_undrstand pharm.
WWW.camargo pharma.com.
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