Questions and Answers
What are possible side effects of 1st Generation Antihistamines?
What is the action of 1st Generation Antihistamines at H1 receptor sites?
Antagonizes the effects of histamine
Diphenhydramine is contraindicated in acute attacks of asthma.
True
Meclizine is indicated for relief of nausea and vomiting associated with __________.
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Which of the following 1st Generation Antihistamines is commonly known as Benadryl?
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Name a common side effect of hydroxyzine.
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Chlorpheniramine is also known as __________.
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Hydroxyzine is contraindicated in patients with hypersensitivity.
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In which situation should meclizine be used cautiously?
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Study Notes
1st Generation Antihistamines
- Indicated for relief of allergic symptoms caused by histamine.
- Act by antagonizing histamine effects at H1 receptor sites.
- Associated with significant CNS depressant and anticholinergic properties.
- Contraindicated in acute asthma attacks.
- Side effects include paradoxical excitation, especially in children, and tinnitus.
- Drug-drug interactions can increase anticholinergic effects when combined with tricyclic antidepressants, quinidine, or disopyramide.
- MAO inhibitors can intensify and prolong the anticholinergic effects.
Diphenhydramine (Benadryl, others)
- Used for allergic symptoms, anaphylaxis, allergic rhinitis, dermatoses, Parkinson's disease, mild nighttime sedation, and motion sickness.
- Acts mainly as an H1 receptor antagonist, providing CNS depression.
- Contraindicated in acute asthma attacks.
- Common side effects include paradoxical excitation in children and tinnitus.
- Interactions with MAO inhibitors and certain antidepressants enhance anticholinergic effects.
Hydroxyzine (Vistaril, others)
- Indicated for anxiety, preoperative sedation, as an antiemetic, and for pruritus.
- Acts as a CNS depressant with antihistaminic, anticholinergic, and antiemetic properties.
- Therapeutic effects include sedation, anxiety relief, and decreased nausea and allergic symptoms.
- Contraindicated in patients with hypersensitivity; may pose risks during pregnancy and lactation.
- Adverse effects include ataxia, wheezing, urinary retention, and chest tightness.
- Can interact with other CNS depressants and medications with anticholinergic properties, intensifying effects.
Meclizine (Antivert, others)
- Primarily indicated for nausea and vomiting related to motion sickness (vertigo).
- Exhibits central anticholinergic and antihistaminic properties, aiding in the decrease of middle ear excitability.
- Hypersensitivity is a contraindication; potential congenital malformations noted in animal studies.
- Use caution in patients with prostatic hyperplasia or angle-closure glaucoma.
- Lactation may be acceptable for occasional use, but prolonged use risks drug effects on infants.
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Test your knowledge on 1st Generation Antihistamines with these flashcards. Each card covers key drugs, their indications, actions, and contraindications. Perfect for students in pharmacology or medical fields.
