Histamine + Anti-Histamine Flashcards
H1 blockers
1st gen
Rx
Chorpheniramine
Diphenydramine
Dimehydrinate
H1 Blockers
2nd gen
Rx
Loratadine
Certirizine
Fexofenadine
Other Drugs
Rx
Cromolyn Sodium
Histidine made from
L-histidine
Histamine metabolism
Released from mast cell/basophils, stored w/ heparin/acidic proteins
RAPIDLY broken down to inactive metabolites (MAO-B)
Autocoid
Released and act locally
Histamine
ALSO: serotonin, inflammatory modulators
Histamine roles
Immune
NT
In periphery widespread: skin/lungs
Histamine activates
- Inflammation
- activates acid-producing parietal cells
- NT central/peripheral
HIstamine
Reaction type?
Type 1 hypersensitivity IgE
H1
Smooth muscle, CNS = up Ca2+
Endothelium = Up NO, cGMP
H2
Vascular smooth muscle
Why histamine released?
Immunologic (type 1, inflammation)
Mechanical (injury)
Drug effects (opiods, meds)
Cromolyn
Blocks histamine release
Histamine
Why smooth muscle contraction but vasodilation?
On H1/h2 smooth muscle, Up Ca2+ constrict
On H1 endothelial cell = releases NO, trumps any contraction
HIstamine
Peripheral effects
- stimulate primary afferent nerve endigns : itch Pain (h1)
* CNS = NT. (Wakefullness, appetite, body temp)
Where can histamine be eaten?
Spoiled scombroid fish
High in histidine –> histamine (bacteria)
S/s: N/V, headache, flushing, sweating
GIVE H1 BLOCKER
Anaphylaxis vs Local allergic
cause?
Systemic = most NOT by histamine (other mediators)
*local = histamine (urticaria, allergic rhitinitis)
Allergy
*subacute, preventative
*Mast cel stabilizer
Tx?
*Subacute, preventative
Inhaled fluticasone
- Mast cell stabilizer - cromolyn sodium
- stop mast cell degranualtion
- nasal spray
*H1 antihistimines
H1 antihistimines
S.E. wakefullness
Some make you awake! (CNS opposite)
H1 antihistimines
Work against other inflammatory mediators?
NO
Asthma- leukotrienes
Motion sickness?
- **dimenhydrinate
- Diphenhydramine
PROPHYLAXIS
1st gen
More anti-chol?
Dyphenhydramine
Dimenhydrinate
LESS chlorpheniramien
1st gen h1 blocker
Little specificity = S.E.
(Blocking what?)
OD?
- chol blocker
- dryness, urinary retention, sinus tach
- a-adrenergic blocker/cardiac
- hypoTN/reflex tach, dizziness
- serotonin
- hungry
- H1
- less inflame/itch/sneeze/rhinorrhea
- less CNS neurotransmission/cognitive
- Sedation
- hungry
NO in GLAUCOMA, PROSTATIC HYPERTROPHY
Toxicity after OD = CNS over cardio S.E. – death w/in hours
H1 blockers
uses
- *Allergic rhinitis/conjunctivitis (2nd GEN)
- *itching/urticaria (2nd GEN)
- atopic derm (some)
- Drug rxns (NO ANAPHYLAXIS)
- Motion sickness/antiemetic
- NO w/ COLD
- local anesthetic (if allergic to others)
- *Sleep aid (1st GEN)
2nd gen H1 blocker
Uses
Allergic rhinitis
Allergic conjunctivitis
Urticaria
1st gen h1 blocker
Uses
Insomnia
Motion sickness
H1 blockers
Absorbtion
*rapid, lipid soluble
*2nd gen ionized at phys pH, up affinity for PGP (p-glycoprotein = pumps right out of cell)
SO METAB IN PERIPHERY, NOT REACHING CNS
Histamines effective for sinus congestion?
NO
H1 blockers
T 1/2?
2nd gen longer
H1 blocker
Metab
Liver to urine
Fexofenadine = liver to bile
H1 Blocker
Clearance
Renal
fexofenadine = bile
H1 blocker
Pregger?
Cross placenta (no risk in preg)
Eliminated in breast milk
Fexofenadine transported by
intestinal OATP1A2 = fruit juice inhibition
Adverse patient population
Elderly - NO 1st GEN
- falls
- incontinence
- altered consciousness/delirium
Infants - NO 1st GEN
*adverse effect, fatalities
H1 1st gen
Daytime use
NOPE
Also no w/ alcohol
Some children get energy
Ex. Benadryl/Sominex (same rx)
Antiemetic
Promethazine
2nd gen antihistimine w/ possible anti-chol + sedation
Cetirizine
H1 blocker
Mech
Inverse agonist
1st gen, which is sleep aid?
Dyphenhydramine
Dyphenhydramine/Dimenhydrinate VS. Chlorpheniramine
D’s = more ANTI-CHOL (and more sedation)
Chlorpheniramine = OTC cold meds
OTC cold meds
Rx?
Chlorpheniramine
1st gen
2nd gen antihistimines
Themes?
Fexophenadine
Loratidine
Cetirizine
- NO ANTICHOL
- NO SEDATION
- LITTLE BBB PENETRATION
