respiratory system pharmacology dr nasim ullah siddiqui

RESPIRATORY SYSTEM PHARMACOLOGY

Dr Nasim Ullah Siddiqui

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DRUGS USED TO TREAT ALLERGIC RHINITIS

Rhinitis is an inflammation of the mucous membranes of the nose and is characterized by sneezing, itchy nose/eyes, watery rhinorrhea, and nasal congestion. An attack may be precipitated by inhalation of an allergen (such as dust, pollen, or animal dander).

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The foreign material interacts with mast cells coated with IgE generated in response to a previous allergen expo-sure .The mast cells release mediators, such as histamine, leukotrienes, and chemotactic factors, that promote bronchiolar spasm and mucosal thickening from edema and cellular infiltration.

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Combinations of oral antihistamines with decongestants are the first-line therapies for allergic rhinitis.Systemic effects associated with these oral preparations (sedation, insomnia, and, rarely, cardiac arrhythmias) have prompted interest in topical intranasal delivery of drugs.

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Antihistamines (H1-receptor blockers)

Antihistamines are the most frequently used agents in the treatment of sneezing and watery rhinorrhea associated with allergic rhinitis.

H1-histamine receptor blockers, such as diphenhydramine, chlorpheniramine , loratadine , and fexofenadine, are useful in treating the symptoms of allergic rhinitis caused by histamine release.

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Ocular and nasal antihistamine delivery devices are available over-the-counter for more targeted tissue delivery. Combinations of antihistamines with decongestants are effective when congestion is a feature of rhinitis.

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Antihistamines differ in their ability to cause sedation and in their duration of action.In general, anticholinergic side effects of the first-generation antihistamines (dry eyes/mouth, difficulty urinating and/or defecating) are transient and may resolve in 7 to 10 days.

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α-Adrenergic agonistsShort-acting α-adrenergic agonists (“nasal decongestants”), such as phenylephrine, constrict dilated arterioles in the nasal mucosa and reduce airway resistance.Longer-acting oxymetazoline administered as an aerosol, these drugs have a rapid onset of action and show few systemic effects.

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Oral administration results in longer duration of action but also increased systemic effects. Combinations of these agents with antihistamines are frequently used. The α-adrenergic agonists should be used no longer than several days due to the risk of rebound nasal congestion (rhinitis medicamentosa).α-Adrenergic agents have no place in the long-term treatment of allergic rhinitis.

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CorticosteroidsCorticosteroids, such as beclomethasone & triamcinolone, are effective when administered as nasal sprays. Topical steroids may be more effective than systemic antihistamines in relieving the nasal symptoms of both allergic and non allergic rhinitis. Treatment of chronic rhinitis may not result in improvement until 1 to 2 weeks after starting therapy.

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Cromolyn(membrane stabilizer agent)Intranasal cromolyn may be useful, particularly when administered before contact with an allergen. To optimize the therapeutic effect of cromolyn, dosing should occur at least 1 to 2 weeks prior to allergen exposure. Due to a short duration of action, cromolyn requires multiple daily dosing.

TREATMENT OF COUGH

By :ISRAA OMAR

COUGH

• It is a protective reflex that removes foreign material and secretion from the bronchi and bronchioles.

• It is very common adverse effect of the angiotensin-converting enzyme inhibitors, in which case ,the drug should be changed in to alternative drug .

• It can be triggered by inflammation in the respiratory system ,for example asthma, pneuomnia,forign body, heart failure, URTI chronic reflux with aspiration, or by neoplasia

ANTITUSSIVE

• Antitussive drugs act by ill defined effect in the brain stem , depressing an even more poorly defined “cough center”.

• All opioid narcotic analgesic have antitussive narcotic analgesic in doses lower than those required for pain relief

• They have minimum analgesic and addictive properties

• Newer agent that only act peripherally on sensory nerves in bronchi are being assessed

CODIENE

• It is the gold standard treatment for cough suppression

• It decreases the sensitivity of cough center in the CNS to peripheral stimuli, decrease the mucosal secretion which thicken the sputum, and inhibit ciliary activity

• These therapeutic effect occur at doses lower than those required for analgesia but still incur common side effect like constipation, dysphoria, and fatigue, in addition to addiction potential

DEXTROMETHORPHAN

• Is a synthetic derivative of morphine that suppresses the response of the central cough center

• It has no analgesic effect, has low addictive profile, but may cause dysphoria at higher doses

• Has significantly better side effect profile than codeine and has been demonstrated to be equally effective for cough suppression

PROTUSSIVES

• Protussives are for wet cough.A) Steam inhalations (alone or with compound benzoin or menthol or eucalyptus oil).B) Expectorants: e.g. Guaifensin These are demulcents and they reduce

viscosity of sputum.

C) Mucolytics e.g. Ambroxol - systemic mucolytics - break disulphide bonds of fibres of sputum

(reduce viscosity of sputum). - have no effect on gastric barriers.

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REFRENCESLIPPINCOTTES PHARMACOLOGY

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respiratory system pharmacology dr nasim ullah siddiqui

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