Antihistamines

Benadryl Name

Diphendyhdramine

What amino acid is associated with allergic responses?

Histamine

Where is the source for majority of Histidine?

Formed in situ

What cells store histamine?

Mast cells

Allergic response greater first or second interaction?

Second

Benadryl is most effective when administered…?

Early

Triple Effect

H1 response in skin. Redding, wheal or disc of edema, large bright crimson flare or halo surrounding wheal

What stops the triple effect?

Anti-H1 drugs

H1 Receptor Locations

Smooth muscle, endothelium, CNS, heart

H2 Receptor locations

GI tract, Gastric acid secretions

H3 receptor locations

CNS, CNS disorders, narcolepsy, ADHD, alzheimers, etc.

H4 Receptors location and response

Immune system, inflammatory conditions.

H1 Receptors Function

Bronchoconstriction, vasodilation, seperation endothelial cells, pain and itching, allergic rhinitis, motion sickness

H2 Receptor Function

Regulate gastric acid secretion, vasodilation

H3 receptor function

Presynaptic feedback of histamine synthesis and release.

H4 receptor function

Mediate mast cell chemotaxis (bone marrow and WBC)

Histamine Antagonists use what type of inhibition?

Competitive, why you must use early

Do anti-histamines have any impact on histamine formation or release?

No

First Generation H1 Antagonists

Cross BBB, sedative effects

Second Generation H1 Antagonists

Decreased BBB = less sedation due to selectivity for peripheral histamines receptors.

First Gen. H1 Drug interactions

Additive to anti-muscarinics, potentiate CNS depressants

First Gen. H1 Absorbed where?

GI Tract for great distribution, eventuall across BBB

Diphenhydramine (Benadryl) is what Gen. H1 Receptor?

First Generation

Tylenol PM, Dramamine, Etc sedative effect from what?

Diphenhydramine (benedryl)

Dramamine use and combination

H1, Motion sickness, benadryl + upper

Piperazine use

Post operative use to come down from sedation side effects.

Promethazine

H1 2nd gen. , but still crosses BBB, Sedation.

Ranitidine (Zantac)

No longer on market, good H2 in stomach, but carcinogenic in acid.

H2 Antagontists MOA

Bind to HIS receptor which blocks cAMP production, leads to less H+ being released.

Drugs for H3 and H4

Not made yet, in development.

Benadryl MOA

Inhibit 5-HT uptake