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When does our body produce Histamine?
produced in response to an allergic reaction or tissue injury
How does Histamine work?
Acts on areas such as the vascular system and smooth muscle, producing dilation of arterioles and an increased permeability of capillaries and venules
After the histamine dilates the arterioles what results?
localized redness and an increased in the permeability of small blood vessels promoting the escape of fluid from them into the surrounding tissue which also causes swelling! <--- termed an Inflammatory Response!!!
What releases histamine and when?
Mast cells release histamen when the body is stimulated by an allergen. (e.g. anaphylactic shock)
Name the three types of histamine cell receptors and what happens to them when stimulated..
- histmaine type 1 = contraction of smooth muscles and dilation of capillaries
- histamine type 2 = the heart and gastric secretions increase
- histamine type 3 = located throughout the nervous system (not sure what happens ..... )
WHat is an antihistamine?
a drug used to block the histmaine cell receptors
What are first-generation antihistamines?
These bind nonselectively to central and peripheral type 1 receptors and may result in CNS stimulation or depression (CNS depression usually occurs with higher doses and allows some of these agents to be used for sedation)
- diphenhydramine (Benadryl)
- promethazine (Phenergan)
Second-generation drugs are selective type 1 receptors and as a group, are less sedating. Name some drugs in this category.
- cetirzine (Zyrtec)
- fexofenadine (Allegra)
- loratadine (Claritin)
Name an anticholenergic effect.
dryness of the mouth, nose, and throat
What is a decongestant?
A drug that reduces swelling of the nasal passages, which, in turn, opens clogged nasal passages and enhances drainage of the sinuses.
What happens when a person overdoses on decongestants?
- CNS depression
Overuse of the topical form of decongestants can cause?
"rebound" nasal congestion: the congestion worsens with use of the drug; relief is felt initially but reoccurs shortly after promting the pt to use the drug more frequently; this perpetuates the the rebound congestion
- Possible Solutions:
- ** nurse may suggestion saline irrigation in nasal passages in place of decongestants
- ** d/c use of deconestants completely or gradually per MD orders
- ** use of oral decongestant instead of topical
Pt education on decongestants includes ...
Overuse of topical nasal decongestants can cause "rebound" nasal congestion and worsen s/s.
Nasal burning and stinging can occur. If this worsens d/c use of drug and discuss with MD (another drug may be recommended)
if using inhalers; warm in hand before use
if s/s don't improve after 7days seek MD or if it's accompanied with fever
don't let tip of container touch the nose