Respiratory: Antihistamines & Antitussives

Question 1

Antihistamine

Answer 1

Histamine effects: mast cells release histamine (causes symptoms of allergies)

Antihistamines are histamine receptor antagonists
-drugs that compete with histamine-

Question 2

Histamine receptor subtypes

Answer 2

H1: antihistamine

H2: reduce gastric acid

Question 3

Antihistamines are H1 or H2 antagonists?

Answer 3

H1

Some also act as anticholinergic drugs.

Question 4

Histamine-mediated disorders

Answer 4

●Allergic rhinitis (hay fever, mould and dust allergies)
●Anaphylaxis
●Angioedema
●Drug fevers- usually young children
●Insect bite reactions
●Urticaria (redness and itching)

Question 5

Antihistamines: Mechanism of Action

Answer 5

Block of H1 receptors prevents the adverse consequences of histamine receptor stimulation

●Vasodilation

●Increased GI and respiratory secretion

●Increased capillary permeability

Question 6

Histamine vs Antihistamine effects

Answer 6

Cardiovascular: small blood vessels
Histamine: Dilation and increased permeability. Swelling.

Antihistamine: Reduce dilation of blood vessels. Reduce increased permeability of blood vessels.

Exocrine Glands
Histamine: Stimulate salivary, lacrimal, and bronchial secretions

Antihistamine: Reduce salivary, lacrimal, and bronchial secretions

Question 7

Antihistamine effects on skin

Answer 7

●reduce capillary permeability
●wheal-and-flare formation
●itching (pruritus)

Question 8

Antihistamine Indications

Answer 8

Palliative, not curative.
treatment of:
●Nasal allergies
●Seasonal or perennial allergic rhinitis (hay fever)
●Allergic reactions
●Motion sickness
●Sleep disorders

Question 9

2 Types of antihistamines

Answer 9

Traditional (introduced 1950s)

Nonsedating/peripherally acting (1980s)

Question 10

Traditional Antihistamines

Answer 10

•Introduced 1950s
•Antagonists of H1 receptor
-Peripherally (reduce respiratory/eye symptoms)
-Centrally (CNS: sedation)
•Have anticholinergic effects
•Nighttime relief

DRUG: diphenhydramine (Benadryl)

Question 11

Anticholinergic (traditional antihistamine) effects/adverse

Answer 11

Drying effect that reduces
●nasal
●lacrimal gland secretions (runny nose, tearing, and itching eyes)
●salivary

ADVERSE:
•Dry mouth (reduced salivary secretions)
●Difficulty urinating
●Constipation
●Changes in vision (dilated pupils, blurred vision)

Question 12

Non-sedating/peripherally acting antihistamines

Answer 12

•Introduced 1980s
•Made to avoid adverse effects (sedation)
•Work peripherally (fewer CNS adverse effects)
•Longer duration of action (increases adherence)

DRUG: Loratadine (Claratin)

Question 13

Antihistamine: Nursing Implications

Answer 13

With use of traditional antihistamines:
•Instruct clients to report excessive sedation, confusion, or hypotension
•Avoid driving
•Do not consume alcohol or other CNS depressants

Question 14

Antitussives

Answer 14

Drugs used to stop or reduce coughing

Opioids, Benylin, Benadryl, and other agents

Used ONLY for nonproductive coughs

Question 15

Antitussives: Opioids

Answer 15

Suppress the cough reflex
●Acts in cough centre of medulla

Examples:
●Codeine
●hydrocodone

Question 16

Antitussives: Common OTC meds

Answer 16

Dextromethorphan (Benylin)
●Synthetic opioid-like compound
●does NOT produce morphine-like effects

Diphenhydramine (Benadryl)
●Antihistamine (H1)

Question 17

Dextromethorphan (Benylin)
Adverse Effect

Answer 17

Drowsiness

(but much less than CNS effect of codeine)

Question 18

Antitussive Agents: Nursing Implications

Answer 18

Report any of the following symptoms:
●cough that lasts more than a week
●persistent headache
●fever
●rash

●Antitussive agents are for nonproductive coughs