Antihistamines

Question 1

Diphenhydramine

Answer 1

H1 histamine receptor antagonist
Uses: allergy, insomnia, motion sickness
Toxicity: sedation (+++), anti-cholinergic activity (+++)
1st generation anti-histamine (penetrates BBB), signals via Gq, not for use in children

Question 2

Hydroxyzine

Answer 2

H1 histamine receptor antagonist
Uses: allergy, anxiety
Toxicity: sedation (+++), anti-cholinergic activity (+++)
1st generation anti-histamine (penetrates BBB), signals via Gq, abuse potential, contraindicated in pregnancy and use with other CNS depressants

Question 3

Brompheniramine

Answer 3

H1 histamine receptor antagonist
Uses: allergy, common cold
Toxicity: sedation (+), anti-cholinergic activity (+)
1st generation anti-histamine (penetrates BBB), signals via Gq, effective for daytime use due to weak sedation

Question 4

Loratidine

Answer 4

H1 histamine receptor antagonist
Uses: allergy
Toxicity: non-sedating, minimal anti-cholinergic activity
2nd generation anti-histamine, better daytime drug than 1st generation, signals via Gq, zwitterionic