Antihistamine Flashcards
Common Cold Causes?
How do they invade?
Most are caused by viral infection (rhinovirus or influenza virus).
Virus invades tissues (mucosa) of upper respiratory tract, causing upper respiratory infection.
What does the Common cold from virus invasion produce?
Cold symptoms?
Excessive mucus production results from the inflammatory response to this invasion (of the viruses).
Fluid drips down the pharynx into the esophagus and lower respiratory tract, causing cold symptoms: sore throat, coughing, upset stomach.
Irritation of nasal mucosa often triggers the?
Mucosal irritation also causes the release of several inflammatory and vasoactive substances, _______ small blood vessels in the nasal sinuses and causing _________
Irritation of nasal mucosa often triggers the sneeze reflex.
Mucosal irritation also causes the release of several inflammatory and vasoactive substances, dilating small blood vessels in the nasal sinuses and causing nasal congestion.
Treatment of common cold or URI (4)
Involves combined use of antihistamines, nasal decongestants, antitussives, and expectorants
Treatment is ________ only, not _________.
_________ treatment does not eliminate the causative _________.
Treatment is symptomatic only, not curative.
(Can only relieve symptoms)
Symptomatic treatment does not eliminate the causative pathogen.
Difficult to identify whether cause is ___ or ____
Treatment is “________” treating the most likely cause
______ and ______ may be used, but a definite viral or bacterial cause may not be easily identified.
Natural health products examples and benefits
Difficult to identify whether cause is viral or bacterial
Treatment is “empirical therapy,” treating the most likely cause
Antivirals and antibiotics may be used, but a definite viral or bacterial cause may not be easily identified.
Natural health products- vitamin C, echinacea, goldenseal- prevent onset of cold symptoms/ decrease severity
In 2009, Health Canada issued recommendations that over-the-counter (OTC) cough and cold products not be given to children younger than __ years of age.
Not effective in small children, and parents are advised to consult their pediatrician on the best ways to manage these illnesses.
6
OTC cough and cold products are not to be given to children younger than 6 due to sedation, seizures, hallucinations, tachycardia and abnormal heart rhythms
Histamines
5 functions
Histamine is a major?
involved in nerve impulse transmission in the CNS
DILATION of capillaries
CONTRACTION of smooth muscle
STIMULATION of gastric acid secretions
ACCELERATE HR
Histamine is a major inflammatory mediator in many allergic disorders, such as rhinitis, anaphylaxis, angioedema, drug fevers, insect bite reactions and urticaria (pale red, raised, itch bumps)
Histamine 1 (H1) receptors
mediate smooth muscle contraction and dilation of capillaries
H2 receptors
mediate acceleration of HR and gastric secretion
Excessive amounts of histamine can cause?
anaphylaxis and severe allergic symptoms
Anaphylaxis and severe allergic 3 symptoms
constriction of smooth muscles in the stomach and lungs
increase in body secretions
vasodilation and increased capillary permeability results in the movement of fluid out of the BVs and into the tissues, causing a drop in BP and edema
Antihistamines [histamine antagonists]
directly compete with histamine for receptor sites
H1 blockers/ H1 antagonists
H1 antagonists drugs
Medications
Treats?
Loratadine and Diphenhydramine
Treats nasal allergies (seasonal hay fever)
Relieves symptoms of the common cold: sneezing and runny nose (can alleviate symptoms but not destroy the virus)
Palliative but not curative
has varying degrees of antihistaminic, antichollinergic, and sedating properties
treats allergies, vertigo, motion sickness, insomnia, and cough
Antihistamines competes with?
Also affects?
histamine for the H1 receptors in the smooth muscle surrounding BVs and bronchioles
secretions of the lacrimal, salivary, and respiratory mucosal glands: primary antichollinergic effects of antihistamines
Loratadine and Diphenhydramine MECHANISM OF ACTION
Compete with histamine for specific receptor sites (Histamine Antagonist)
-Bind to histamine receptors on mast cells & basophils
-Prevent further release of histamine & actions
H1 BLOCKERS or H1 antagonists (known as antihistamines)
- ASSOCIATED WITH
- LOCATION
H1 blockers are associated with antihistamines
H1 are in areas such as smooth muscle surrounding blood vessels and bronchioles
Loratadine and Diphenhydramine
H1 antagonists drugs
also cause ____ effects
Also affects secretions of lacrimal, salivary and respiratory mucous glands which are the primary anticholinergic actions (dry mouth, etc.) of antihistamine
Antihistamine mechanism of action
during an allergic reaction, histamines are released from mast cells and basophils in response to an antigen in blood.
Histamine then binds and activates other cells in the nose, eyes, respiratory tract, GI tract, and skin producing allergy symptoms
In the respiratory tract, histamine causes extravascular smooth muscle (bronchial tree) to contract (while antihistamines cause it to RELAX)
Histamine can cause pruritus by stimulating nerve endings (antihistamine can alleviate itching)
circulating histamine binds to histamine receptors on basophils and mast cells which further stimulates the release of histamine
Antihistamine blocks histamine receptors on surfaces of basophils and mast cells and prevents the release and action of histamine
They do not remove histamine already bound but compete for the unoccupied receptors
(better if given early in a histamine-mediated reaction before all histamine binds to cell membrane receptors)
consequences of histamine binding are?
vasodilation
increased GI, respiratory, salivary, and lacrimal secretions
increased capillary permeability with edema
Binding of H1 blockers (antihistamines) to these receptors PREVENTS?
Vasodilation
increased GI, respiratory, salivary, and lacrimal secretions
Increased capillary permeability with resulting edema
The allergen binds to antibodies— causes HISTAMINE SECRETION:
- swelling of BVs and releasing of fluids
- congestion—insufficient 02—sleepiness, weakness, drowsiness, snoring, headache
OR
- swelling of BVs and releasing of fluids
- nasal irritation—infection/ inflammation—sinusitis, asthma, inflammation of middle ear
ANTIHISTAMINES INDICATION
nasal allergy
seasonal/ perennial allergic rhinitis
common cold
allergic reactions
motion sickness
PD(due to antichollinergic effects)
Vertigo
Sleep aids
Antihistamines action
Mediate’s inflammatory response:
Rhinitis: hay fever, mold, dust
Anaphylaxis
Angioedema
Drug fevers
Insect bite reactions
Urticaria (itching)
Symptoms of common cold
-sneezing
-Runny nose
The anithistaminic, anticholinergic and sedative properties also make them useful for treatment of:
Vertigo
Insomnia
Motion sickness
cough
Antihistamines are most effective when
Most effective when given early in histamine mediated reactions
Antihistamines should not be used as sole therapy in?
Should not be used as sole therapy in acute asthma attacks
Antihistamines Contraindication
Narrow angle glaucoma
Heart disease
Hypertension
COPD
Peptic ulcer disease
Seizure disorders,
BPH (enlarged prostate)
pregnancy
NOT to be used as sole therapy for asthma attack
Pediatric Alert
______ is not recommended in children under 6 yrs
______ is not recommended in children
______is not recommended in children under 2 yrs
Fexofenadine (Allegra) is not recommended in children under 6yrs
Desloratadine (Aerius) is not recommended in children
Loratadine (Claritin) is not recommended in children under 2 yrs
Recommend to discontinue antihistamine at least 4 days prior to allergy testing
Antihistamines Adverse Effects
Drowsiness (varies amongst drug class)
Sedative effects
“Drying” effects
Dry mouth
Difficulty urinating
Constipation
Change in vision
Cardio: dysrhythmias, hypotension, palpitations, syncope, sedation, dizziness, muscular weakness, excitement, nervousness, seizures
GI: N & V, diarrhea, constipation, hepatitis
Antihistamines Interactions
Medications
Food
Loratadine drug interactions: Ketoconazole, cimetidine and erythromycin increase concentrations of fexofenadine & loratadine
Diphenhydramine: Alcohol, CNS depressants, MAOs increase depressant effects of cetirizine (Reactine) and diphenhydramine (Benadryl)
Cardiovascular small blood vessels
Histamine effects- dilates BVs, increases BVs permeability (allow substances to leak into tissues)
Antihistamine effects: reduces dilation of BVs
Smooth muscle exocrine glands
Histamine: stimulate salivary, gastric, lacrimal, and bronchial secretions
Antihistamine: reduces salivary, gastric, lacrimal, and bronchial secretions
Immune
Histamine effects- released from mast cells; results in allergic reaction
Antihistamine: does not stabilize mast cells/ prevent the release of histamine; but does bind to histamine receptors and prevents the action of histamine
Nonsedating antihistamines medications
Function
Loratadine
cetrizine
fexofenadine
eliminate many adverse effects, esp. sedation
Act peripherally to block actions of histamine and therefore have significantly less CNS effects
also called peripherally acting antihistamines because they do not readily cross blood-brain barrier
has a longer duration of action
Loratadine:
Drug class?
nonsedating antihistamine [takken OD]
does not distribute to CNS which diminishes sedative effects
High doses can cause drowsy, headache, and fatigue
relieves seasonal allergic rhinitis (hay fever) and chronic urticaria
CONTRA: allergy
Traditional antihistamines
works both peripherally and centrally
has antichollinergic effects, which in some cases is more effective than non-sedating antihistamines
diphenhydramine, dimenhydrinate
used alone/ in combination
treats nausea/ motion sickness
causes drowsiness
Diphenhydramine hcl
acts peripherally and centrally
antichollinergic and sedative effects
used as a hypnotic drug because of its sedating effects
Not for OAs due to the risk of falls [hangover effects]
the greatest range of therapeutic indication
relief/ prevention of allergies, motion sickness, treatment of PD, and promotes sleep
used in conjunction with EPi for anaphylaxis and treats dystonia
CONTRA: allergy
CAUTION: nursing mothers, newborns, lower respiratory tract symptoms
Nasal Congestion
Excessive nasal secretions
Inflamed and swollen nasal mucosa
Primary causes: Allergies & Upper respiratory infection (common cold)
Decongestants
Three separate groups of nasal decongestants:
taken orally to prevent system effect (prolonged effects and delayed onset), inhaled/ topically into the nose
adrenergic (sympathomimetics)
anticholinergic (parasympatholytic)
corticosteroids (intranasal steroids)
Decongestants
ORAL route
NASAL
prolonged decongestant effects, onset is delayed and effect is less potent than topical
Nasal- can cause rebound congestion because of the rapid absorption of the drug through mucous membranes followed by a rapid decline in effectiveness
Adrenergics (sympathomimetics) medications 2
Pseudoephedrine (Sudafed) oral
**Oxymetazoline HCl (Dristan) nasal spray
Anticholinergics (parasympatholyitcs)
Ipratropium bromide (Atrovent) nasal spray
Corticosteriods medications
Fluticasone propionate (Flonase) nasal spray
Beclomethasone dipropionate (Rivanase) (nasal spray)
Budenoside (Pulmicort, pulmicort turbohaler, symbicort turbohaler)
Decongestants mechanism of actions
shrink engorged nasal mucous membranes and relive nasal stuffiness
Adrenergics (sympathomimetics) mechanism of action
Constrict small arterioles (BVs around nasal sinuses)
(when BVs are stimulated by adrenergic drugs- they constrict)
Once BVs shrink, the nasal secretions in the swollen mucous membrane are better able to drain
Corticosteriods mechanism of action
Target inflammatory response elicited by invading organisms/ antigen; the body responds to invaders by producing inflammation to isolate area and call other cells to destroy invader
Steroids exert anti-inflammatory effects by causing cells to be turned off/ rendered unresponsive
“turn off” cell response; reduce inflammatory symptoms to improve patient comfort and air exchange
Anticholinergics action
Inhibits secretions of the serous and serous-mucous membranes of the nasal passages
Decongestant indications
acute/ chronic rhinitis
common cold
sinusitis
hay fever
allergies
reduces swelling of nasal passages before surgery
Decongestants
Contraindications of adrenergic drugs
Narrow angle glaucoma
Uncontrolled cardiovascular disease
Hypertension
Diabetes
Hyperthyroidism
Prostatitis, BPH
Inability to close eyes (stroke patients)
TIAs
Asthma
Drugs allergy
Adverse effect of Adrenergics (think adrenergic stimulation)
Nervousness
Insomnia
Palpitations
Tremor
AE of Corticosteriods
Localized dryness, nose bleeds, mucosal thinning
AE of anticholinergic
Also excessive dryness, nose bleeds
MAOIs may result in additive pressor effect with ______ decongestants
MAOIs may result in additive pressor effect with adrenergics decongestants- raise BP