Drugs Used in Cough and Asthma 233to isoprenaline. It is given by oral as well as
inhalation route by nebulizer. Palpitation,
restlessness, nervousness are the common
side effects with salbutamol.
TERBUTALINE
It is highly selective β 2 agonist similar
to salbutamol, useful by oral as well as in-
halational route.
SALMETEROL
It is newer long acting selective β 2 adr-
energic agonist with slow onset of action,
used for maintenance therapy in asthma,
nocturnal asthma and asthma induced by
exercise.
The β 2 selective adrenergic agonists
are most widely used drugs for the treat-
ment of asthma. They are effective after
oral and inhaled administration and have
a longer duration of action. Albuterol
(salbutamol), salmeterol, bitolterol, pir-
buterol are available as aerosol pack in
metered dose.
BAMBUTEROL
It is a latest selective adrenergic β 2 ago-
nist with long plasma half life and given
once daily in a dose of 10-20 mg orally.
METHYLXANTHINES (THEOPHYLLINE AND ITS
DERIVATIVES)Among the methylxanthines, aminophylline
is most commonly used drug in the treat-
ment of bronchial asthma. It is a stable mix-
ture of theophylline and ethylenediamine.
These drugs inhibit the enzyme phosphod-
iesterase, this inhibition results in higher
concentration of intracellular cyclic AMP.
Increased cAMP leads to bronchodilatation,
cardiac stimulation and vasodilatation.Pharmacological Actions
CNS: The caffeine and theophylline are
pharmacologically CNS stimulants and pro-
duce alertness and cortical arousal, but in
higher doses causes restlessness, nervous-
ness and insomnia.
CVS: Methylxanthines stimulate the
heart and increase the force of myocardial
contraction. Tachycardia is more common
with theophylline. Cardiac output is
increased in CHF patients.
Smooth muscles: Methylxanthines relax
smooth muscles especially bronchi in
asthmatic patients. Theophylline produces
sustained bronchodilator action.
Kidney: Methylxanthines exert mild
diuretic action by inhibiting tubular
reabsorption of sodium and water, In
addition, it increases renal blood flow and
glomerular filtration rate.
Skeletal muscles: Methylxanthines
facilitate neuromuscular transmission by
increasing acetylcholine release.
Mast cells: Methylxanthines inhibit the
release of histamine and other mediators
from mast cells which indirectly help in the
management of bronchial asthma.THEOPHYLLINE
Theophylline has two distinct action:
smooth muscle relaxation (i.e. bronchodi-
latation) and suppression of the response
of the airways to stimuli (i.e. non-bron-
chodilator prophylactic effects). Bron-
chodilatation is mediated by inhibition of