Pharmacology for Dentistry

Drugs Used in Cough and Asthma 235

drop) is used in allergic conjunctivitis

in chronic cases.

KETOTIFEN

It is a cromolyn analogue. It is an
antihistaminic (H 1 antagonist) and probably
inhibits airway inflammation induced by
platelet activating factor (PAF) in primate.
It is not a bronchodilator. It is used in asthma
and symptomatic relief in atopic dermatitis,
rhinitis, conjunctivitis and urticaria. It is
absorbed orally and well tolerated.
Bioavailability is 50% due to first pass
metabolism and is primarily metabolized.
The common side effects include dry
mouth, sedation, dizziness and nausea.

CORTICOSTEROIDS

Like mast cell stabilizer, corticosteroids do
not relax airway smooth muscle directly but
reduce bronchial reactivity, increase air-
way caliber, suppress inflammatory
response to antigen antibody reaction or
trigger stimuli and reduce the frequency
of asthma exacerbations. They produce
more sustained symptomatic relief than any
bronchodilator and mast cell stabilizer.

Systemic steroids are used in both se-
vere chronic asthma and in acute emergen-
cy of asthma (status asthmaticus).

Among the inhaled steroids,
beclomethasone is a halogenated corticoster-
oid ester used in aerosol form. It suppresses
asthma by a topical antiinflammatory action
without causing any systemic side effects.
They reduce the bronchial hyperreactivity

and increase the peak expiratory flow rate in

asthmatic patients. They are not effective

during an acute attack or in status

asthmaticus. Side effects are sore throat,

hoarseness of voice, dysphonia, oropharyn-

geal candidiasis.

LEUKOTRIENE PATHWAY INHIBITORS

Apart from histamine, leukotrienes liberated

during inflammation are more powerful

bronchoconstrictor and longer acting.

Leukotrienes also increase bronchial mucus

secretion and increase vascular permeability.

All the leukotrienes are derived from 5-

lipoxygenase pathway of arachidonic acid

and are synthesized by a variety of

inflammatory cells in the airways e.g.

eosinophils, mast cells, basophils and

macrophages. The LTB 4 , C 4 & D 4 exert many

effects known to occur in bronchial asthma,

including bronchoconstriction and increased

bronchial reactivity. The drug, montelukast

(LTB 4 antagonist) and zafirlukast (LTD 4

antagonist) have the advantage of being used

when taken orally in asthmatic patients.

MONTELUKAST

It is a cysteinyl leukotriene receptor

antagonist indicated for the management of

persistent asthma. It has been shown to have

substantial blockade of airway leukotriene

receptors 24 hours after oral dosing. Mon-

telukast appears to be a useful alternative

or adjunct to inhaled corticosteroid therapy

in adults and an alternative to sodium cro-

moglycate in children.