Antihistamines and Antitussives

Question 1

Types of antihistamines

Answer 1

Compete with histamine for receptor sites - antagonist

Two histamine receptor subtypes

1. H1 (allergic reaction) **
   - Some also act as anticholinergic drugs
2. H2

Question 2

What causes histamine to be released?

Answer 2

Mast cells release histamine and other substances as a response - allergic reactions

Question 3

Histamine-mediated disorders

Answer 3

• Allergic rhinitis
• Anaphylaxis
• Angioedema
• Drug fevers
• Urticaria (redness and itching)

Question 4

What happens when the H1 receptor is blocked from the antihistamine?

Answer 4

Adverse consequences of histamine are prevented, like:

• Vasodilation
• Increased GI and respiratory secretion
• Increased capillary permeability

Question 5

Hist vs. Antihist - Cardio

Answer 5

Histamine
- Dilation and increased permeability of small vessels - allowing fluid to leak into tissues

Antihistamine

• Reduce dilation of blood vessels
• Reduce increased permeability of blood vessels

Question 6

Hist vs. Antihist - Exocrine

Answer 6

Histamine
- Stimulates salivary, lacrimal, and bronchial secretions

Antihistamine

• Reduce “” secretions
• Causes a drying effect that wil help with runny nose, tearing, and itching eyes (lacrimal glands)

Question 7

Antihist - Skin

Answer 7

• Reduces capillary permeability
• Wheal-and-flare formation
• Pruritus (itching)

Question 8

Antihist - Anticholinergic

Answer 8

• Only some antihistamines

- Blocks ACh receptor sites

Question 9

Antihist - Indications

Answer 9

Palliative, not curative, treatment

• Nasal allergies
• Seasonal allergic rhinitis
• Allergic reactions
• Motion sickness
• Sleep disorders

Question 10

Traditional Antihistamines - Indications

Answer 10

diphenhydramine (Benadryl) - chlorpheniramine

Causes sedation, used in nightime relief

• Has an anticholinergic effect
• Antagonist of H1 receptor.

Question 11

Traditional Antihist - Adverse Effects

Answer 11

Anticholinergic effects

• Dry mouth
• Difficulty urinating
• Constipation
• Changes in vision (dilated pupils, blurred vision)

Question 12

Nonsedating/Peripherally Acting Antihistamines

Answer 12

Loratadine (Claritin)

• Works peripherally which means fewer CNS adverse effetison
• Longer duration of action (increases adherence)
• Eliminates sedation

Question 13

Antihist - Nursing Implications

Answer 13

• Patients should report excessive sedation, confusion, or hypotension
• Don’t consume alcohol or other CNS depressants

Question 14

Types of Cough

Answer 14

1. Productive cough
   - Congested, removes excessive secretions
2. Nonproductive cough
   - Dry cough

Cough reflex - initiated by irritation of sensory receptors in the respiratory tract

Question 15

When should you not use Antitussives?

Answer 15

When you have a productive cough

Question 16

Antitussive - Mechanism of Action

Answer 16

Opioids - suppresses the cough reflex, acts in the cough centre of the medulla
- Eg. Codeine

Synthetic opioid-like compounds

• do not produce morphine-like effects
• Eg. Dextromethorphan

Question 17

Antitussives - Adverse Effects

Answer 17

Codeine
- Sedation, nausea, vomiting, lightheadedness, constipation*

Dextromethorphan (Benylin)

• Dizziness, drowsiness*, nausea
• Much less than CNS effects of codeine

Question 18

Antitussives - Nursing Implications

Answer 18

Report symptoms to caregiver

• Cough that lasts more than a week*
• Persistent headache
• Fever*
• Rash