Antihistamines

Question 1

Diphenhydramine

Answer 1

• first generation

- marked sedation; anti-motion sickness (but not as good as Scopolamine); antitussive; OTC sleep aid

Question 2

Pyrilamine

Answer 2

• first generation

- moderate sedation; OTC sleep aid

Question 3

Hydroxyzine

Answer 3

• first generation

- marked sedation

Question 4

Chlorpheniramine

Answer 4

• first generation

- OTC cold remedy; slight sedation

Question 5

Promethazine

Answer 5

• first generation

- marked sedation; anti-emetic

Question 6

Fexofenadine

Answer 6

• second generation
• metabolite of Terfenadine, originally removed from the market because of risk of QT prolongation and cardiac arrhythmias

Question 7

Loratadine

Answer 7

• second generation

Question 8

Cetirizine

Answer 8

• second generation

Question 9

Cimetidine

Answer 9

• H2 antagonist
• OTC
• significantly increases bioavailability of ethanol by inhibiting gastric first-pass metabolism
• drug interactions via CYP450 metabolism (warfarin, phenytoin, TCAs, metronidazole, etc)
• adverse effects:
  1. CNS delirium and confusion particularly in the elderly
  2. Antiandrogenic effects - gynecomastia, galactorrhea, reduction in sperm count and reversible impotence
  3. Blood dyscrasias
  4. Common to all H2 blockers - diarrhea, dizziness, somnolence, headache, rash, liver toxicity (elevated liver enzymes)

Question 10

Ranitidine

Answer 10

• H2 antagonist
• OTC
• less likely to interfere with CYP450 drug metabolism than Cimetidine
• significantly increases bioavailability of ethanol by inhibiting gastric first-pass metabolism

Question 11

Famotidine

Answer 11

• H2 antagonist
• OTC
• no effect on the bioavailability of ethanol

Question 12

Nizatidine

Answer 12

• H2 antagonist
• OTC
• significantly increases bioavailability of ethanol by inhibiting gastric first-pass metabolism