FB - H1 Antihistamines Flashcards

1
Q

A patient’s urticaria is interfering with sleep. Which class of drugs would be most appropriate to take before bed?

A

A first-generation antihistamine (e.g., promethazine). A first-generation antihistamine will cross the blood-brain barrier (BBB) and cause sedation helping the patient to sleep.

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2
Q

Which class of antihistamine drugs would be most appropriate for a patient with nausea and vomiting?

A

A first-generation antihistamine. A first-generation antihistamine will cross the blood-brain barrier (BBB) and block histamine H1 and muscarinic M1 receptors to control nausea and vomiting.

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3
Q

A 28-year-old taxi driver presents with allergic rhinitis. Suggest an appropriate antihistamine drug.

A

Fexofenadine, desloratadine or loratadine. Any second or new generation antihistamine that does not cause sedation would be appropriate.

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4
Q

A 73-year-old patient with mild cognitive impairment presents with urticaria. Suggest an appropriate antihistamine drug?

A

Fexofenadine, desloratadine or loratadine. Any second or new generation antihistamine that does not cross the blood-brain barrier (BBB) to cause sedation and block muscarinic cholinergic receptors in the CNS.

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5
Q

Use of promethazine is contraindicated in children under the age of 2 years old because of increased risk of…

A

Respiratory depression

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6
Q

For how long should patients be warned not to drink fruit juice after taking fexofenadine?

A

4 hours before dosing and 1-2 hours after dosing

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7
Q

List THREE drugs that should be avoided or taken only with caution together with all first-generation antihistamines.

A

Alcohol, opioid analgesics, antidepressants and any other CNS depressant drugs

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8
Q

Which class of antihistamine would be preferable for the treatment of
urticaria in a patient with narrow-angle glaucoma?

A

Second or third/new generation antihistamines without muscarinic receptor antagonism

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9
Q

What is the duration of action of MOST 2nd generation antihistamines?

A

12 to 24 hours

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10
Q

What is the duration of action of MOST 1st generation antihistamines?

A

4 to 6 hours

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11
Q

First-generation antihistamines can increase the risk of drug-induced long QT syndrome (LQTS) because of actions at…

A

HERG potassium channels

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12
Q

What are the major histamine receptors on mast cells?

A

H1 and H4

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13
Q

Why do 1st generation antihistamines cause sedation?

A

They cross the blood-brain barrier and inhibit H1 histamine receptors in the CNS. Inhibition of muscarinic receptors in the CNS may additionally further contribute to drowsiness/sedation.

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14
Q

The triple vascular response of Lewis includes

A

Flush, Flare and Wheal

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15
Q

Histamine triggers the formation of a wheal (a raised swelling on the skin) due to increased…

A

Vascular permeability

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16
Q

Histamine triggers the formation of a flush due to…

A

Dilation of blood vessels and disruption of capillaries

17
Q

Allergens trigger mast cell degranulation by…

A

Cross-linking FcεR1-bound IgEs

18
Q

List at least THREE examples of 1st generation antihistamines

A

Chlorpheniramine, Triprolidine, Ketotifen, Diphenhydramine, Promethazine

19
Q

List at least THREE examples of 2nd generation antihistamines

A

Cetirizine, Loratadine, Fexofenadine

20
Q

List at least TWO examples of drugs sometimes considered 3rd or new generation antihistamines

A

Levocetirizine, Desloratadine

21
Q

Which histamine receptors on c-afferents and in the CNS contribute to itch?

A

H1 and H4

22
Q

In terms of agonist or antagonist activity, what kind of drugs are clinically used as antihistamine drugs?

A

Inverse agonists

23
Q

Which second-generation antihistamine is most likely to still cause some sedation?

A

Cetirizine (and also acrivastine) are less sedating that first-generation antihistamines but still notably more sedating than fexofenadine and loratadine.

24
Q

Why do 2nd generation antihistamines cross the blood-brain barrier (BBB) less?

A

2nd generation antihistamines are less lipophilic and/or have greater affinity for the P‐glycoprotein efflux pump than 1st generation antihistamines

25
Q

List at least THREE adverse effects of first-generation antihistamines

A

Sedation, dry mouth, GIT disturbances, weight gain, tachycardia, postural hypotension