Sympathomimetics (Adrenergic Agents) 137system effects than ephedrine. It has agonist
activity at both β 1 and β 2 adrenoceptors,
leading to increased cardiac output and
relaxation of bronchial smooth muscle.
It is readily and completely absorbed
from the GIT following oral administration
with no presystemic metabolism.
Pseudoephedrine is rapidly absorbed
throughout the body. It is eliminated largely
unchanged in urine by N-demethylation.
It is excreted in breast milk at
concentration constantly higher than those in
maternal plasma. The elimination of
pseudoephedrine is reduced in renal
impairment. Hepatic dysfunction is unlikely
to affect the pharmacokinetics of the drug.
Adverse effects include excessive
tiredness, restlessness, nervousness,
tremors, headache, palpitation, elevation in
BP, vomiting, anorexia, constipation, nausea
and convulsions.
It is contraindicated in cardiovascular
disease causing hypertension, angina pectoris
etc., endocrine disorders like hyperthyroidism,
diabetes mellitus, prostate enlargement and
concurrent use of MAO inhibitors.
It is indicated in symptomatic relief from
stuffed nose, respiratory tract congestion,
bronchospasm associated with asthma,
bronchitis and other similar disorders.
OXYMETAZOLINE
It is a directly acting sympathomimetic
amine used in symptomatic relief in nasal
congestion which increases mucosal
secretion.
Local vasoconstriction is normally
achieved within 5 to 10 minute of intranasal
administration. Oxymetazoline enters
tissues rapidly and is released slowly. The
plasma half life is 5-8 days. 30% of absorbed
drug is eliminated in the urine and
approximately 10% in the faeces.It is used:- As a nasal decongestant in allergic
rhinitis, with or without the addition of
antazoline or sodium chromoglycate. - As a nasal decongestant in sinusitis, in
otitis media where there is evidence of
obstruction of the eustachian tube
especially in subacute serous otitis
media and otitic barotrauma. - As an ocular decongestant in allergic
conjunctivitis. - To ‘whiten’ an inflamed (red) eye
caused by a local irritant such as dust
or following the removal of a foreign
body.
Adverse effects include local stinging or
burning, sneezing, dryness of mouth and
throat. Prolonged use may cause rebound
congestion and drug induced rhinitis,
headache, tachycardia may occur.
Compounds like naphazoline and
xylometazoline are relatively selective α 2
agonists, which on topical application
produce local vasoconstriction. They are
used as nasal decongestants and have
longer duration of action. Prolonged use
can produce atrophic rhinitis and anosmia.
ISOPRENALINE
It is beta-receptor stimulant, which
stimulates the heart and causes tachycardia.
It relaxes the smooth muscles particularly
the bronchial and GIT. It is mainly used in
bronchial asthma, in the treatment of shock
and as a cardiac stimulant in heart block.