Chapter 74 Antihistamines Flashcards
What are the primary histamine receptors involved in allergic reactions?
H1 and H2 receptors
H1 receptors are associated with allergic symptoms, while H2 receptors are related to gastric acid secretion.
What triggers the release of histamine from mast cells and basophils?
Allergic and nonallergic mechanisms
Nonallergic release can occur without prior allergen exposure.
What are the symptoms of allergic rhinitis caused by H1 stimulation?
- Sneezing
- Rhinorrhea
- Pruritus
- Nasal congestion
- Conjunctivitis
- Sinusitis
- Asthma
What type of antibodies are produced following exposure to an allergen in allergic rhinitis?
IgE antibodies
These antibodies attach to mast cells and basophils, leading to inflammatory mediator release upon re-exposure.
What are the two types of allergic rhinitis?
- Seasonal (hay fever)
- Perennial
What are the classes of drugs used to treat allergic rhinitis?
- Glucocorticoids (nasal)
- Antihistamines (oral or nasal)
- Cromolyn (nasal)
- Sympathomimetics (oral or nasal)
- Anticholinergics (nasal)
- Antileukotrienes (oral)
What is the most effective treatment for rhinitis?
Intranasal glucocorticoids
They prevent the inflammatory response to allergens.
What are the adverse effects of intranasal glucocorticoids?
- Drying of nasal mucosa
- Sore throat
- Epistaxis
- Headaches
- Rare: adrenal suppression and slowing of linear pediatric growth
Name one first-generation antihistamine.
Diphenhydramine
Other examples include brompheniramine and promethazine.
What is the action of antihistamines?
Block H1 receptors (receptor antagonist)
They relieve sneezing, rhinorrhea, and nasal itching but do not reduce nasal congestion.
True or False: Second-generation antihistamines are non-sedating.
True
They have low lipid solubility and cannot cross the blood-brain barrier.
What is the recommended use of intranasal cromolyn?
Prophylactically before symptoms start
It suppresses the release of histamine and other inflammatory mediators.
What is the action of oral sympathomimetics?
Activate alpha-1 adrenergic receptors on nasal blood vessels
This reduces nasal congestion by shrinking swollen membranes.
What are the adverse effects of oral sympathomimetics?
- Rebound congestion
- CNS stimulation
- Cardiovascular effects
- Stroke
- Abuse
What is the main function of antitussives?
Elevate cough threshold in the CNS
Name one opioid antitussive.
Codeine
Another example is hydrocodone.
What is the function of expectorants?
Render cough more productive by stimulating flow of respiratory tract secretions
What is the common treatment for the common cold?
Rest and hydration
There is no cure; treatment focuses on symptom relief.
What should be avoided in children younger than 6 years regarding cold remedies?
Over-the-counter cold remedies
Only use products labeled for pediatric use.
