Antihistamines Flashcards
Doxylamine
Insomnia, Allergies
Highly Sedating
Large doses can cause arrhythmias (QT Prolongation)
Avoid in elders
First Generation H1 Antihistamine
Diphenhydramine
Insomnia, Allergies
Highly Sedating
Large doses can cause arrhythmias (QT Prolongation)
Avoid in elders
First Generation H1 Antihistamine
Cyclizine
Motion Sickness
Vertigo
Mildly Sedating
First Generation H1 Antihistamine
Meclizine
Motion Sickness
Vertigo
Mildly Sedating
First Generation H1 Antihistamine
Chlorpheniramine
Allergies Moderately sedating Possible paradoxical CNS stimulation Often found in combo w/ cold products avoid in elders
First Generation H1 Antihistamine
Brompheniramine
Allergies Moderately sedating Possible paradoxical CNS stimulation Often found in combo w/ cold products avoid in elders
First Generation H1 Antihistamine
Hydroxyzine HCL
Allergies Urticaria
Mild - moderate sedation
First generation H1 antihistamine
Hydrozyzine PAMoate
Insomnia
Anxiety
Mild - moderate sedation
First generation H1 antihistamine
Histamine H1 Receptor
Location , Action
Location - Bronchial smooth muscle, CNS, Endothelium, cardiac muscle
Action - sleep wake cycle, learning, memory, stimulate nerve endings, bronchoconstriction, vasodilation of blood vessels, contraction smooth muscle
Mainly thinking histamine on H1 causes:
- Bronchoconstriction
- Increases bowel peristalsis
- Increased vasodilation permeability
Histamine H2 Receptor
Location , Action
Location - parietal cells of stomach, cardiac muscle, CNS
Action - Gastric acid production
H3 Receptor
Location, Action
Location - CNS, peripheral tissue
Action - modulation of neurotransmitter release
H4 receptor
Location, Action
Location - basophils, bone marrow, SI, colon, spleen, thymus
Action - facilitates made cell chemotaxis
Cardiovascular Effects of Histamine
Mast cells are present in normal cardiac tissue (higher presence in diseased hearts)
Histamine enhances influx of Ca into cardiac myocytes =
- increase contractility
- tachycardia
- hypotension secondary to vasodilation
Antihistamine actions on H1
Bronchodilaiton
Constipation
Anti-itch, reduce pain
Reduced the inflammatory / allergic response
Antihistamine actions on H2
Suppression of gastric acid production
First Generation H1 Antihistamines
- Treats
- Features
Used to treat allergic symptoms, motion sickness & insomnia
Poor receptor selectivity
Highly lipophilic = crosses BBB = interfere w/ histaminergic transmission
Leads to many ADRs limiting its use
Second Generation H1 antihistamines
Used to treat allergic symptoms
Highly selective for H1 Receptor with no anticholinergic effects
Minimall or non-seriating
- limited penetration to BB
Preferred in elders
Rapid onset of action about a hour
Longer duration of action
Azelastin
Nasal Spray - RX
Second Generation H1 antihistamines
Local application to nose - less associated systemic side effects
Location irratation can occur (nasal irritation, nose bleeds, Bitter taste)
Avoid use if any preexisting damage to the nasal passage
Olopatidine
Nasal Spray - Rx
Second Generation H1 antihistamines
Local application to nose - less associated systemic side effects
Location irratation can occur (nasal irritation, nose bleeds, Bitter taste)
Avoid use if any preexisting damage to the nasal passage
Fexofenadine
Second Generation H1 antihistamines
Oral, OTC
Highest safety profile = b/c not metabolized by CYP450
Not metabolize
Excreted in feces
useful in pt on a lot of medication b/c not a lot DDI
Avoid in grapefruit juice, orange & apple juice
- must separate by at least 4 hours
Cetirizine
Second Generation H1 antihistamines
Oral, OTC
Most SOMNOLENCE!
active metabolite of hydroxyzine
Not metabolized via CYP450 but both are PgP substrates
Watch DDI grapefruit juice
Avoid other sedative drugs — additive effects
Loratitdine
Second Generation H1 antihistamines
Oral , OTC
Metabolized by 3A4
check for 3A4 inhibitors
Levocetirizine
Second Generation H1 antihistamines
Oral , OTC
active metabolite of cetirizine
Not metabolized via CYP450 but both are PgP substrates
Watch DDI grapefruit juice
Avoid other sedative drugs — additive effects
Desloratidine
Second Generation H1 antihistamines
Oral, RX
Least likely to cause somnolence
active metabolite of loratadine
Most likely for DDI because hepatic ally metabolized
