Mast Cell Stabilizers

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Chapter: Essential pharmacology : Drugs for Cough and Bronchial Asthma

It is a synthetic chromone derivative which inhibits degranulation of mast cells (as well as other inflammatory cells) by trigger stimuli. Release of mediators of asthma like histamine, LTs, PAF, interleukins, etc. is restricted.


MAST CELL STABILIZERS

 

Sodium Cromoglycate (Cromolyn Sod.)

 

It is a synthetic chromone derivative which inhibits degranulation of mast cells (as well as other inflammatory cells) by trigger stimuli. Release of mediators of asthma like histamine, LTs, PAF, interleukins, etc. is restricted. The basis of this effect is not well understood, but may involve a delayed Cl¯ channel in the membrane of these cells. Chemotaxis of inflammatory cells is inhibited. Long term treatment decreases the cellular inflammatory response; bronchial hyperreactivity is reduced to variable extents. Bronchospasm induced by allergens, irritants, cold air and exercise may be prevented. However, AG:AB reaction is not interfered with. It is also not a bronchodilator and does not antagonize constrictor action of histamine, ACh, LTs, etc. Therefore, it is ineffective if given during an asthmatic attack.

 

Pharmacokinetics

 

Sod. cromoglycate is not absorbed orally. It is administered as an aerosol through metered dose inhaler delivering 1 mg per dose: 2 puffs 4 times a day. The earlier spin-haler capsule formulation delivering the drug as a fine powder has become less popular. Only a small fraction of the inhaled drug is absorbed systemically; this is rapidly excreted unchanged in urine and bile.

 

Uses

 

Bronchial Asthma: Sod. cromoglycate is used as a long term prophylactic in mild to moderate asthma. Decrease in the frequency and severity of attacks and improvement in lung function is more likely in extrinsic (atopic) and exercise induced asthma, especially in younger patients. Therapeutic benefit (when it occurs) develops slowly over 2–4 weeks and lasts 1–2 weeks after discontinuing. However, the prophylactic effect of cromoglycate is less marked and less consistent than that of corticosteroids. Its popularity has declined.

 

Allergic Rhinitis: Cromoglycate is not a nasal decongestant, but regular 4 times daily prophylactic use as a nasal spray produces symptomatic improvement in many patients after 4–6 weeks: need for nasal decongestants is reduced.

 

Allergic Conjunctivitis: Regular use as eye drops is beneficial in some chronic cases.

 

FINTAL inhaler: 1 mg metered dose aerosol; 2 puffs 4 times daily.

FINTAL nasal spray: 2% aqueous solution; 2 squeezes in each nostril QID.

FINTAL eye drops: 2% aqueous solution; 1 drop in each eye QID.

CROMAL5 INHALER: 5 mg metered dose aerosol, 2 puffs 4 times daily.

 

Adverse Effects

 

Because of poor aqueous solubility, absorption of cromoglycate is negligible; systemic toxicity is minimal. Bronchospasm, throat irritation and cough occurs in some patients, especially with fine powder inhalation. Rarely nasal congestion headache, dizziness, arthralgia, rashes and dysuria have been reported.

 

Ketotifen

 

It is an antihistaminic (H1) with some cromoglycate like action; stimulation of immunogenic and inflammatory cells (mast cells, macrophages, eosinophils, lymphocytes, neutrophils) and mediator release are inhibited. It is not a bronchodilator, but produces sedation.

 

After 6–12 weeks of use, it reduces respiratory, symptoms in ~ 50% patients of bronchial asthma, but improvement in lung function is marginal. It also produces symptomatic relief in many patients with atopic dermatitis, perennial rhinitis, conjunctivitis, urticaria and food allergy. Thus, it is especially indicated in patients with multiple disorders.

 

Ketotifen is absorbed orally; bioavailability is 50% due to first pass metabolism. It is largely metabolized; t½ is 22 hours.

 

Adverse Effects

 

Generally well tolerated. Sedation and dry mouth are common. Other side effects are dizziness, nausea, weight gain.

 

Dose: 1–2 mg BD; children 0.5 mg BD.

 

ASTHAFEN, 1 mg tab, 1 mg/5 ml syrup; KETOVENT 1 mg tab.

 

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