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Questions and Answers
Which first generation H1 antihistamine is characterized by being highly lipophilic and able to penetrate the blood-brain barrier?
What strategy was used to decrease the sedation effect of first generation H1 antihistamines?
Which type of H1 antihistamines can penetrate the blood-brain barrier and bind to central H1-histamine receptors?
What is a characteristic of most second generation H1 antihistamines in relation to the blood-brain barrier?
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At pH = 7.4, are first generation Ethylenediamines protonated or not?
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How does the size of alkyl substituents affect the selectivity for histamine receptors vs cholinergic receptors in first generation Ethanolamine ethers?
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Which type of derivatives are more potent among Propylamine or alkylamine derivatives in first generation H1 antihistamines?
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How does E-Pyrrobutamine compare to Z-Pyrrobutamine in terms of potency in first generation H1 antihistamines?
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What is the important amino acid for interacting with the carboxylate group in second generation H1 antihistamines?
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Which compound is a zwitterionic at physiologic pH and does not easily penetrate the blood-brain barrier?
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What is the predominant charge status of Cetirizine at physiological pH?
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Which compound is a prodrug of Loratadine?
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Study Notes
First Generation H1 Antihistamines
- Diphenhydramine is a highly lipophilic first-generation H1 antihistamine that can penetrate the blood-brain barrier.
Decreasing Sedation Effect
- The strategy used to decrease the sedation effect of first-generation H1 antihistamines is to reduce their ability to penetrate the blood-brain barrier.
Characteristics of H1 Antihistamines
- First-generation H1 antihistamines can penetrate the blood-brain barrier and bind to central H1-histamine receptors.
Second Generation H1 Antihistamines
- Most second-generation H1 antihistamines are characterized by their inability to penetrate the blood-brain barrier.
Ethylenediamines
- At pH 7.4, first-generation Ethylenediamines are protonated.
Selectivity of Receptors
- Increasing the size of alkyl substituents in first-generation Ethanolamine ethers increases their selectivity for histamine receptors vs cholinergic receptors.
Potency of Derivatives
- Among Propylamine and alkylamine derivatives in first-generation H1 antihistamines, alkylamine derivatives are more potent.
E- and Z-Pyrrobutamine
- E-Pyrrobutamine is less potent than Z-Pyrrobutamine in first-generation H1 antihistamines.
Interaction with Carboxylate Group
- Glutamic acid is the important amino acid for interacting with the carboxylate group in second-generation H1 antihistamines.
Zwitterionic Compound
- Fexofenadine is a zwitterionic compound at physiologic pH and does not easily penetrate the blood-brain barrier.
Charge Status of Cetirizine
- Cetirizine is predominantly zwitterionic at physiological pH.
Prodrug of Loratadine
- Descarboethoxyloratadine is a prodrug of Loratadine.
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Description
Test your knowledge of H1 antihistamines in Medicinal Chemistry I with this quiz. Identify first generation antihistamines, their activities, and chemical structures.
