4 - Respiratory & Allergy Drugs 1

Common cold

• What is it?

• Cause

• Mechanism/symptoms(5)

• A mild, self-limited upper respiratory tract infection

• Viruses that infect the nasal mucosa

• The viruses infect the nasal mucosa and kill the epithelial cells, triggering an immune response. This includes vasodilation, which leads to increased redness and swelling, and increased permeability, which allows fluid/proteins to leak into the tissue, causing edema which shows up as nasal congestion. Another effect is rhinorrhea via signaling goblet cells to make mucus. Another effect is sneezing/sore throat because the inflammatory mediators trigger sensory nerve endings as a reflex, and finally, fever can happen as a result of inflammatory cytokines.

Match the symptom to the drug

Rhinorrhea, sneezing

Nasal congestion

Cough

Fever

Rhinorrhea, sneezing: Antihistamine

Nasal congestion: Decongestant

Cough: Cough treatment

Fever: Antipyretic(acetaminophen/NSAIDs)

Antibiotics __ for treatment of common cold

ARE NOT recommended

Common cold vs allergic rhinitis

1. Cause: Common cold is from virus, allergic rhinitis is due to allergens

2. Symptoms: Allergic rhinitis doesn’t come with fever, and mucus is always clear. Allergic rhinitis also has no cough, usually consecutive sneezing with itching, while common cold has a cough

Histamine normal function(4)

Stored in mast cells/basophils, and when released:

1. Triggers vasodilation and increases vascular permeability

2. Increases constriction of smooth muscle(Airways, gut)

3. Acts on sensory nerve endings in skin/mucosa → itch, sneezing

4. Triggers glands to secret mucus

First generation H1-antihistamine

• Mechanism

• Results

• Difference from second generation

• Names(3)

• Inverse agonist of H1 histamine receptors

• Results

  • Reduces redness, swelling, whealing, and nasal congestion due to stopping vasodilation and vascular permeability

  • Keeps smooth muscle relaxed, helping bronchodilation

  • Blocks stimulation of nerves, reducing itching and sneezing

  • Blocks stimulation of mucus glands, reducing rhinorrhea(Stronger than second-generation anti-histamines, dries up mucus due to also having an anti-muscarinic effect)

• Crosses the blood-brain-barrier and causes drowsiness

• Chlorpheniramine(CPM, most used), Hydroxyzine(ลมพิษ), Ketotifen, Brompheniramine, Triprolidine

Second/third generation H1-antihistamine

• Mechanism

• Results

• Difference from first generation

• Names(Generic + brand)

• Inverse agonist of H1 histamine receptors

• Results

  • Reduces redness, swelling, whealing, and nasal congestion due to stopping vasodilation and vascular permeability

  • Keeps smooth muscle relaxed, helping bronchodilation

  • Blocks stimulation of nerves, reducing itching and sneezing

  • Blocks stimulation of mucus glands, reducing rhinorrhea(Weaker than first generation anti-histamines due to a lack off anti-muscarinic effect)

• Doesn’t cross the blood brain barrier, no drowsiness

• Cetirizine(Zyrtec), Levocetirizine(Xyzal), Loratadine(Claritine), Desloratidine(Aerius), Fexofenadine(Telfast), Bilastine(Bilaxten)

How often do we take anti-histamines per day?

• First generation: 3x a day

• Second generation: 1x a day

Anti-histamine ADRs

1. Dry mouth/eyes(1st gen)

2. Urinary hesitancy, usually in older men with BPH(1st gen)

3. Glaucoma/ต้อหิน(1st gen)

4. Sedation(1st gen, mild in cetirizine)

5. Confusion/cognitive impairment(1st gen), but some children actually get stimulated

6. QT prolongation → Ventricular arrhythmia(1st gens taken off the market)

Pseudoephedrine

• Route

• Class

• Mechanism

• ADRs

• Oral

• Decongestant

• Binds alpha1 receptors to boost vasoconstriction and reduce leakiness of blood vessels → decongestant

• Elderly, hypertension, sympathetic nervous system boosting, ale restrictions

Pseudoephridine substitute

Phenylephrine

Oxymetazoline

• Route

• Class

• Mechanism

• ADRs

• Intranasal(Drop or spray)

• Decongestant

• Binds alpha-1 adrenergic receptors to boost vasoconstriction and reduce vessel leakiness

• Dryness(can cause epistaxis), rebound congestion after over 5 days of use(rhinitis medicamentosa)

Intranasal steroids

• Why are they used in allergy only?

• Because they take 1-2 weeks to take effect

Why do we need decongestants if we already have anti-histamines?

• Because anti-histamines only inhibit the vasodilation/leakiness mediated by histamines, not other inflammatory mediators like leukotrines, etc.

How long until a cough is considered chronic, and why is that important?

• 3 weeks, and it’s important because we should now see if there’s an underlying cause

Productive vs non-productive cough treatment

• A productive cough indicates it’s effectiveness in clearing out something stuck inside our throats, so it’s good, and shouldn’t be suppressed

Guaifenesin

• Route

• Class

• Mechanism

• ADRs

• Oral

• Drugs affecting mucociliary factors

• An expectorant, aka increases volume/fluidity of secretions that are made so they’re easier to clear

• No serious ones

Bromhexine

• Mechanism

• Mucolytic

Acetylcysteine

• Route

• Class

• Mechanism

• ADRs

• Oral/IV

• Drug affecting mucociliary factors

• A mucolytic, aka cuts up existing mucus to make it easier to cough up, but also is used as an antidote for paracetamol poisoning

Levodropopizine

• Class

• Mechanism

• Drug affecting the afferent limb of the cough reflex

• ตามนั้น

Codeine

• Route

• Class

• Mechanism

• ADRs

• Oral

• Drugs affecting central cough mechanism

• Analgesia and raising threshold of cough reflex in the medulla

• Drowsiness, constipation, addiction

Dextromethorphan

• Route

• Class

• Mechanism

• ADRs

• Oral

• Drugs affecting central cough mechanism

• Raising threshold for cough reflex in the medulla, albeit via blocking an excitatory receptor

• Milder drowsiness, constipation

Morphine

• Route

• Class

• Mechanism

• ADRs

• Oral, IV, IM, subcutaneous

• Drugs affecting central cough mechanism

• A stronger analgesic and cough suppressant than codeine. Suppresses cough via raising threshold for cough reflex

• Drowsiness, constipation, addiction

Tiffy/Decolgen

• What is it?

• Avoid taking with

• Tiffy dey/Decolgen prin is __

• Paracetamol 500 mg + chlorpheniramine(2mg)

• Paracetamol involved drugs

• Tiffy dey/decolgen prin = Tiffy/decolgen with phenylpehrine

Paracetamol

• Other name

• Simple mechanism

• Acetaminophen

• Analgesic/antipyretic: Not an NSAID, but thought to inhibit COX pathway in CNS

Nasal spray tips

• Look down

• Spray away from nasal septum(more vascularity there)

• Breathe in gently