CAM201 Lecture Notes - Lecture 14: Post-Nasal Drip, Pseudoephedrine, Tachycardia
12 Jun 2018
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Department
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Treatet of Upper Respiratory Tract
Ifectios
The Common Cold
− Symptoms include malaise, cough, rhinorrhea (runny nose), sore throat,
rhinitis
− Symptoms typically peak 1-3 days and last 7-10 days
− Children get around 5-10 colds/year
− Adults get around 2-4 colds/year
− Most common responsible virus in rhinovirus
Rhinitis
− Irritation and inflammation of the mucous membrane inside the nose
− Symptoms include stuffy nose, runny nose, sneezing, and post-nasal drip
(dripping from nose to throat)
− Causes of rhinits:
Common Cold Treatment
− Development of vaccinations and antivirals largely unsuccessful due to
different rhinovirus antigenic types
− Virus is self-limiting, and treatment involves alleviating symptoms
Oral Decongestants
Pseudoephedrine
− To treat blocked nose and sinuses
Mechanism of Action
− Indirect acting sympathomimetic- increased CNS activity
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− Pseudoephedrine has weak actions on adrenoreceptors, but it resembles NA
enough to be transported into nerve terminals by norepinephrine transporter
(NET)
− Once in the nerve terminals, the pseudoephedrine is taken up into vesicles by
vesicular monoamine transporter (VMAT), replacing NA and causing it to be
released into the cytoplasm
− The released NA in the cytoplasm is released into the synapse by NET in
exchange for pseudoephedrine to act on postsynaptic receptors
− This results in NA accumulation in the synapse (increased activity on
postsynaptic receptor), and it accumulates at the presynaptic nerve terminal,
which increases the NA availability to escape into the synapse via uptake 1
Clinical Effects
1. Decongestant Effects
− Increased heart rate
− Increased forced of myocardial contraction
− Increased BP
− Increased CNS stimulation (potential for abuse, precursor for
methamphetamine)
2. Non-specific Adrenergic Effects
− Increased NA at α1 receptors causes vasoconstriction, leading to shrinkage
of swollen mucous membranes
Adverse Effects
− Increased CNS stimulation
− Excitability
− Insomnia
− Tremor
− Tachycardia
− Palpitations
− Increased BP
Precautions
− CVD patients
− Prostatic hypertrophy
− Diabetes
− Hyperthyroidism
− Patients taking MAO inhibitor antidepressants
Phenylephrine
Mechanism of Action
− α1 receptor agonist, causes shrinkage of swollen mucous membranes-
decongestant effects
Clinical Use
− Many manufacturers have reformulated their products from pseudoephedrine
to phenylephrine due to potential abuse of pseudoephedrine to produce
methamphetamine
− It is safer and has fewer adverse effects than pseudoephedrine
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