Lecture 7: OTC Cough and Cold Flashcards
What do Pharmacological mechanisms of actions fundamentally begin with?
A drug receptor interaction
What four types of ingredients do commonly available cough and cold medications contain?
- Decongestants
- Cough suppressants
- Expectorants
- Anti-pyretics
What are OTC cough and cold medications used to treat?
Symptoms of upper respiratory infections (runny nose, congestion, cough, fever)
What is the purpose of the coughing reflex?
To clear the breathing passage of irritants, microbes, fluids and mucus
What is the function of the mucus in the upper respiratory tract?
The mucus is protective. It provides a barrier between the lumen of the airway and the epithelium
Why is mucus upregulated during infection?
To prevent penetration of those microbes and to provide substance to clear garbage out of the lungs and airways
Why would it be bad to suppress cough during bacterial infections?
Because the cough is used to get that bacteria out
What happens when you cough with viral infections?
You end up aerosolizing the particles because they’re so small
What is the coughing reflex initiated by?
The stimulation of sensory nerves innervating the throat and lungs
Which receptors in the throat detect irritation?
P2X3 and TRPV1
Where do the sensory neurons in the throat that detect irritation send their information?
To the cough center in the medulla oblongata
What happens after irritation is sent to the cough center in the medulla?
Efferent nerves via parasympathetic and motor nerves stimulate the diaphragm, intercoast muscles and lung to initiate a cough
What is the main nerve that stimulates the cough reflex?
CNX the vagus nerve
What are Anti-tussives?
OTC drugs that inhibit the cough reflex
How do most anti-tussives work?
By inhibiting neurons in the medulla oblongata
What are the three approved anti-tussives?
- Dextromethorphan
- Diphenhydramine
- Codeine
What is Codeine in terms of receptors?
A mu opioid receptor agonist
Where are Mu opioid receptors located?
In the medulla oblongata (cough center) and peripheral nerves innervating the respiratory tract
What is the most abundant opioid receptor in the CNS?
Mu
What is meant by codeine is a mu opioid receptor agonist?
Codeine activates opioid receptors
What kind of receptors are Opioid receptors?
They are inhibitory G-protein coupled receptors (GPCRs)
What happens when opioid receptors are activated by Codeine?
They inhibit calcium channels, activate K+ channels and inhibits adenylate cyclase which inactivate neurons and reduces neurotransmitter release in the cough center of the medulla
Which part of the CNS does Codeine act on?
The cough center of the medulla
Why are antitussives that contain codeine not recommend for those under 18?
Because they have undesirable effects like addiction and overdose. An can inhibit other brain areas like breathing area
What is codeine converted to in the CNS?
Morphine
How does Dextromethorphan work at the receptor?
It is a centrally active NMDA receptor antagonist
What are NMDA receptors?
Ligand gated ion channels gated by glutamate that allow sodium and calcium through and activates neurons
Which neurons does Dextromethorphan inhibit?
Neurons in the medulla oblongata like codeine
What is a brand name of Deztromethorphan?
Buckley’s!
What are the Pharmacological characteristics of Diphenhydramine?
It is an antihistamine (H1 inverse agonist)
What kind of receptors of H1 receptors?
Gq coupled GPCRs
Where are H1 receptors located?
On respiratory smooth muscles
What do H1 receptors do?
They stimulate sensory nerves to produce coughing
What does Diphenhydramine do to H1 receptors?
It inhibits histamine action at the receptors
Besides at H1 receptors how else does Diphenhydramine work?
It crosses the BBB to suppress the medullary cough center
What is the common decongestant?
Pseudoepinephrine
What is Pseudoepinephrine?
A decongestant
What are the pharmacological characteristics of Pseudoephedrine?
It is an agonist at the alpha and beta adrenergic receptors
What is Pseudoephedrine very similar to?
Norepinephrine
What is meant by Pseudoephedrine being sympathomimetic?
It mimics the effect of Norepinephrine adrenergic receptors
What kind of responses does Pseudoephedrine activate?
Fight or flight type responses
How does Pseudoephedrine affect alpha adrenergic receptors?
It leads to vasoconstriction of blood vessels in the respiratory tract causing less mucus release
How does Pseudoephedrine affect beta adrenergic receptors?
It causes smooth muscle relaxation leading to dilation of the bronchi
What is the overall effect of Pseudoephedrine?
- Shrinks swollen nasal mucus membranes
- reduces tissues hyperemia (blood flow)
- Reduces edema
- Reduces nasal congestion
What happens if too much of Pseudoephedrine is taken?
Because it affects beta adrenergic receptors there will also be heart affects which is an off target effect
What is Pseudoephedrine structurally related to?
Meth and can be used a precursor to create meth
What is different between Pseudoephedrine and Phenylephrine?
Phenylephrine is a specific alpha adrenergic receptor agonist
What effects will Phenylephrine have?
It will cause vasoconstriction of the nasal mucosa but not smooth muscle relaxation
What are Expectorants?
Oral drugs that enhance the clearance of mucus
What is Guaifenesin?
An expectorant
What does Guaifenesin do?
Increases the output of the bronchial secretions by decreasing the adhesiveness and surface tension
What is the suggested mechanism of Guaifenesin?
It acts as an irritant of gastric vagal receptors that recruit efferent parasympathetic reflexes causing glandular exocytosis that is comprised of a less viscous mucus mixture
