Antihistamines Flashcards
Histamine effects
- CNS nerve impulse transmission
- capillary dilation
- smooth muscle contraction
- secretion simulation
- ⬆HR
H1 function
smooth muscle constriction in blood vessels
increase cap permeability
too much histamine
anaphylaxis & severe allergy sx
smooth muscle constriction of the stomach and lungs
increase in body secretions
vasodilation and increased cap permeability
when is histamine released?
when there are antigens in the blood
histamine can also trigger the release of more histamine
histamine antagonists
H2 blockers (GERD agents)
H1 blockers (antihistamines)
properties of antihistamines
anthistaminic
anticholinergic
sedative
antihistamine uses
allergies
urticarial (hives)
S/S of common cold and cough
vertigo and motion sickness
insomnia
when should antihistamines be started?
early, before histamine starts to bind
AE
mainly drowsiness
SE
dry mouth
changes in vision
urinary retention/hesitancy
constipation
(anticholinergic)
Loratadine (claritin)
non-sedating
daily
allergic rhinitis and urticaria
lower dose for elderly and renal dz
not for kids <2
few anticholinergic and sedative properties
Diphenhydramine (Benadryl)
- peripheral and central
- high in anticholinergic and sedative properties
- tx of many d/o including insomnia and motion sickness
- tx of anaphylaxis and dystonia when used with epinephrine
- caution in mothers, neonates, lower respir sx/dz, asthma, or risk for pneumonia
- PO, parenteral, topical
- dries secretions
nursing implications
- increased viscosity can occlude airways
- paradoxical rx in older adults
- take w/ food
- tx of dry mouth
- caution w/ other OTC cold meds
- monitor BP
- brain fog (no driving, etc)
paradoxial reaction
irritability
dizziness
confusion
sedation
hypotn
antihistamine MOA
-block H1(histamine) receptors
-inhibit smooth muscle constriction in blood vessels, respir, and GI tract
-decrease capillary permeability
