Antihistamines

Question 1

1st Gen antihistamines effects

Answer 1

varying degree of anticholinergic effect:

- sedation at low dose or CNS excitment at high

Question 2

Name 1 Ethylene diamine (1st gen) drug and 1 that you would find in the states?

Answer 2

Pyrilamine (antihist, pyrihist)

USA: Tripelennamine

Question 3

Name 3 Ethanolamine human drugs used in animals

Answer 3

Diphenhydramine (benedryl)
Dimenhydrinate (gravol, dramamine)
not approved in canada (human drugs prescribed by vets)

Clemastine (tavist)

Question 4

Name 1 Alkylamine drug

Answer 4

Choropheniramine (cold meds like chlor-tripolon)

- antidepressent properties (inhibits serotonin uptake)

Question 5

Name 2 piperazine drug

Answer 5

Trimeprazine
- found in vanectyl P

Hydroxyzine

Question 6

2nd Gen antihistamine effect

Answer 6

more selective for perihperal H1 receptors
longer half life and dosing interval
non-drowsy (more P-gly substrates, less CNS effects)

Question 7

Name 2nd Gen human meds used in animals

Answer 7

Cetrizine (zyrtex) - piperazine class
Loratidine (claratin)

Question 8

Clinical use of H1 blockers

Answer 8

• modulate allergic reactions (before contact)
• reduce bronchocontriction (dogs)
• antidote for “extrapyramidal reactions” causes by phenothiazine traq
• therapy for anaphylaxis (not replace epi)
• therapy for dogs with mast cell tumors (prevent pruritis)

Question 9

2 other inflammatory mediator (autocoids and their antagonist)

Answer 9

Cyproheptadine (periactin)

• blocks H1 receptor an dserotonin receptor
• used for photic head shaking in horses
• appetite stimulant in cats (not great)

Cromolyn sodium
- mast cell stabilizing agents