Patho- Pharm: Histamine

What is Histamine?

- Natural chemical in body

- Found in skin, lungs, GI tract

- Released during allergic reactions

Histamine Effects

- Redness (vasodialation)

- Swelling (capillary leak)

- Itching and Mucus

- Bronchoconstriction

H1 Histamine Receptor

- Allergy symptoms

H2 Histamine Receptor

- Increases stomach acid

What are H1 blockers?

- Antihistamines

First gen anthistamines: Examples and Anticholinergic

- Examples: Diphenhydramine (Benadryl)• Cause sedation

- Anticholinergic effects: dry mouth, urinary retention

Second gen antihistamines

- Examples: Cetirizine, Loratadine, Fexofenadine

- Much less sedation

- Fewer side effects

Antihistamines use for

- Used for mild allergy symptoms

When are Antihistamines used

- Mild allergies

- Motion sickness

- Common cold (to reduce runny nose)

- Not effective for anaphylaxis

Side effects of Antihistamines

- Sedation (less with 2nd gen)

- Dizziness or confusion

- GI upset (take with food)

- Anticholinergic effects

Contraindications for Antihistamines

- Avoid in pregnancy (3rd trimester)

- Avoid in breastfeeding

- Avoid in newborn

- Use caution: children, older adults,BPH, glaucoma

whst is used for ansphylaxis

- Antihistamines DO NOT treat anaphylaxis

- Epinephrine is the drug of choice