Lecture 13 - OTC Cough and Cold Flashcards
commonly available over the counter cough and cold medications contain either singly or in combination a:
decongestant, cough suppressant, expectorant, and/or antipyretic/analgesic
cough and cold medications are used to treat:
symptoms of upper respiratory infections
a reflex to clear the breathing passage of irritants, microbes, fluids, and mucus
coughing
coughing is a common symptom of:
upper respiratory tract viral infections
the coughing reflex is initiated by:
stimulation of sensory nerves innervating the throat and lungs
sensory neurons in the throat and lungs send stimulatory information to the ______ in the ______
nucleus tractus solitarus (nTS), brainstem medulla oblongata
efferent neurons via the _____ stimulate the diaphragm, intercostal muscles, and lungs to initiate a cough
parasympathetic and motor neurons
over the counter drugs that inhibit the cough reflex (antitussives) do so mostly by:
inhibiting neurons in the nucleus tractus solitarus (nTS)
what is codeine?
a mu opioid receptor agonist
mu opioid receptors are located in the:
nucleus tractus solitarus (nTS) and peripherial nerves innervating the respiratory tract
opioid receptors are:
inhibitory GPCRs (Gi-GPCR)
activation of opioid receptors leads to:
inhibition of adenylate cyclase –> neuronal inactivation and reduced neurotransmitter release
why is opioid use so dangerous?
opioid receptors are also located in the brainstem regions that mediate the breathing reflex (preBotzinger complex); high dose opioids inhibit the breathing reflex
what is dextromethorphan?
a centrally active NMDA receptor antagonist
what is the function of dextromethorphan?
inhibits neurons in the nucleus tractus solitarus (nTS)
a ligand gated ion channel gated by glutamate
NMDA receptor
how effective is dextromethorphan at treating a cough?
not very
what is diphenhydramine?
an antihistamine (H1 inverse agonist)
H1 receptors are:
Gq coupled GPCRs
where are H1 receptors located?
respiratory smooth muscles
inhibits histamine action at H1 receptors and crosses the blood brain barrier in the nucleus tractus solitarus (nTS)
diphenhydramine
what is the most effective, but not dangerous, antitussive?
honey
type of receptor located on vascular arterioles and cause vasoconstriction when activated
alpha-1 adrenergic receptors
type of receptor located on vascular arterioles and veins, as well as broadly throughout the central nervous system
alpha-2 adrenergic receptors
type of receptor located on the bronchioles and in the heart
beta adrenergic receptors
alpha-1 adrenergic receptors are:
Gq coupled GPCRs
alpha-2 adrenergic receptors are:
Gi couples GPCRs
beta adrenergic receptors are:
Gs coupled GPCRs
both alpha-1 receptors and alpha-2 receptors lead to:
smooth muscle contraction
how is it that both alpha-1 and alpha-2 receptors can cause smooth muscle contraction?
- for alpha-1, activation of Gq proteins increase PLC and IP3 pathways; this stimulates the release of calcium and smooth muscle contraction
- for alpha-2, inhibition of adenylate cyclase reduces cAMP, which increase MLCK activation and increases smooth muscle contraction
what is pseudophedrine?
a non-specific agonist at the alpha and beta adrenergic receptors
a drug that looks like an endogenous agonist, and produces effects similar to activation of the sympathetic nervous system
sympathomimmetic drug
pseudopherine activates alpha adrenergic receptors in the mucosa of the respiratory tract leading to:
vasoconstriction of blood vessels
pseudophedrine activity at beta adrenergic receptors causes:
smooth muscle relaxation leading to dilation of the bronchi and increased mucociliary clearance
what are the overall effects of pseudophedrine?
shrinks swollen nasal mucous membranes, reduces tissue hyperemia, edema, and nasal congestion
pseudophedrine is structurally related to _____ and has stimulant proterties
amphetamine
what is phenylephrine?
a specific alpha-1 adrenergic receptor agonist
what is the main difference between phenylephrine and pseudoephedrine?
both cause vasoconstriction in the nasal mucosa, but phenylephrine does not lead to smooth muscle relaxation in the bronchi or impact the heart
which is technically the more effective decongestant, phenylephrine or pseudoephedrine?
pseudoephedrine
is there an abuse liability with the use of phenylephrine?
no, because it cannot be transformed into methamphetamine
what is oxymetazoline?
an alpha-2 adrenergic agonist
how is oxymetazoline administered?
as a spray (delivered directly to the nasal mucosa means more rapid onset of action and avoids side effects of a systemically administered alpha-2 adrenergic agonist)
what is a risk of prolonged use of oxymetazoline?
rhinitis medicamentosa (aka rebound congestion)
what are expectorants?
oral drugs that enhance the clearance of mucus
what is the only available expectorant today?
guaifenesin (mucinex)
increases the output of bronchial secretions by decreasing the adhesiveness and surface tension
guifenesin
what is guaifenesin derived from?
bark from the guiac tree
what is the mechanism of action of guaifenesin?
unknown
