Antihistamines Flashcards
name the cells that secrete histamine in the following locations:
a. skin, mucous membranes, lung, blood vessels
b. circulating blood
c. gastric mucosa
d. brain
histamine secretion:
a. mast cells - skin, mucous membranes, lung, blood vessels
b. basophils - circulating blood
c. enterochromaffin-like cells - gastric mucosa (regulation of gastric acid secretion)
d. histaminergic neurons - brain
what 2 metabolites of histamine can be detected in urine?
- via oxidative deamination —> lmAA
- via methylation + oxidation —> methyl lmAA
(1-methyl-4-imidazoleacetic acid)
(for example, if someone was having a massive allergy attack)
in mast cells and basophils, histamine is bound in ____
in ECL cells (enterochromaffin-like cells, stomach) and histaminergic neurons, histamine is stored in _____
mast cells/ basophils - histamine in cytoplasmic granules
ECL/neurons - histamine in vesicles
4 mechanisms (causes) of histamine release
- immune response: antigens bind IgE on surface of pre-sensitized mast cells and basophils, causing degranulation
- mast cell injury (rapid, local release)
- endocrine/ neuronal (ECL cells of stomach mucosa, histaminergic neurons)
- chemical displacement: stimulate direct release of histamine from mast cells (without pre-sensitization) - displaces histamine from cytoplasmic granules
*major concern because a rapid, severe reaction can occur (anaphylactic shock)
describe what happens in initial and subsequent exposure during IgE-mediated histamine release
Type I hypersensitivity response
Initial exposure = sensitization, IgE bind mast cells and basophils
subsequent exposure - antigen cross-links with IgE on mast cell/basophil surface, causing histamine release
(+ other primary/secondary inflammatory mediators from these cells)
what is the distribution of the 4 histamine receptor subtypes, and what are their respective post-receptor signaling and effects?
H1: smooth muscle, endothelium, peripheral afferent neurons, postsynaptic histaminergic neurons —> G(alpha)q —> increase IP3, DAG —> itch, pain, vasodilation, edema, etc
H2: parietal cells, cardiomyocytes, smooth muscle, mast cells, basophils, postsynpatic histaminergic neurons —> G(alpha)s —> increase cAMP —> gastric acid secretion, vasodilation, tachycardia, negative feedback
H3: presynaptic histaminergic neurons, myenteric plexus —> G(alpha)i —> decrease cAMP —> decrease NT release
H4: WBC —> G(alpha)i —> decrease cAMP —> differentiation of WBC precursors, chemotaxis, cytokine secretion, adhesion factor upregulation
what effect does histamine have on the CNS and peripheral sensory nerve terminals, respectively?
histamine effects:
CNS: NT (H1/2/3), circadian/feeding rhythms, appetite/satiety (H1/3), wakefulness (H1/3), modulator of NT release (H3)
peripheral sensory nerve terminals: depolarization of afferent nerve endings causing itch/pain (H1), urticarial response (to stinging insects/plants), sneezing trigger
3 effects of histamine on cardiovascular system (and which receptors mediate)
- vasodilation:
- H1: NO production
- H2: smooth muscle cAMP production
- increased capillary permeability: H1 (contraction of vascular endothelial cells, allowing fluid/cell escape), decrease in blood pressure
- heart:
- reflex tachycardia: indirect response to histamine-mediated decrease in systemic bp
- H2 -mediated direct increase in force/rate of cardiac contraction
which histamine receptor mediates histamine effect on respiratory system?
H1 signaling —> bronchoconstriction
patients with asthma are hypersensitive to histamine/ other inflammatory mediators (leukotrienes)
which histamine receptors mediate histamine effects on digestive system?
H1 signaling —> contraction of intestinal smooth muscle (may cause diarrhea)
H2 signaling —> gastric acid secretion from parietal cells and mucus secretion in intestines
spoiled scombroid fish or meat, sardines, fermented foods, beans, nuts, and cocoa based products are high in this inflammatory mediator
histamine
H1 histamine receptor induces _____ signaling
what biological effects does this have?
H1: Ga(q) signaling —> increase IP3 and DAG
effects: itch (pruritus), pain, mucosal secretion, bronchoconstriction, edema, contraction of gut, vasodilation
an increase in gastric acid secretion, vasodilation, heart rate, and negative feedback of histamine release is mediated through which receptor and signaling pathway?
H2: Ga(s) signaling —> increased cAMP
found on parietal cells, cardiomyocytes, mast cells and basophils, poststynaptic histaminergic neurons
which histamine receptor is found on PRE-synaptic histaminergic neurons, and what signaling pathway does it activate?
H3: pre-synaptic histaminergic neurons, myenteric plexus
induces Ga(i) signaling —> decrease cAMP (—> and NT release)
which two histamine receptors cause a decrease in cAMP?
H3: presynaptic histaminergic neurons
H4: WBC
both induce Ga(i) —> decrease cAMP
what is the role of signaling through H4 histamine receptor (biological consequences)?
H4: found on WBC, signal through Ga(i) —> decrease cAMP
effects: differentiation of myeloblasts and promyelocytes, chemotaxis, cytokine secretion, upregulation of adhesion factors
allergic rhinitis and conjunctivitis, allergic bronchospasm (bronchoconstriction), urticaria (hives), and anaphylaxis are due to the actions of ______
histamine
all these pathologies are due to vasodilation, increased capillary permeability, and edema in different parts of the body
(anaphylaxis is due to systemic distribution of allergen - these effects seen everywhere)
3 pharmaceutical strategies to block histamine action
- antihistamines: specific for H1 and H2 only (not enough alone due to other inflammatory mediators released in granules)
- inhibitors of mast cell degranulation: block Cl- channels, inhibiting Ca2+ mobilization and degranulation (must be inhaled - inhalers or nasal spray, can prevent asthma attacks) —> Cromolyn and Nedocromil
- Epinephrine (and other drugs that counteract histamine action): agonist of alpha/beta adrenergic receptors, powerful mediator of bronchodilation and vasoconstriction (treatment for anaphylaxis)
1st generation vs 2nd generation H1 antihistamines
1st generation: neutral/hydrophobic at physiological pH (readily cross BBB), highly sedative, anti-emetic (nausea) and anti-itch, short acting
2nd generation: ionized at physiological pH, not sedative or anti-emetic, highly selective, longer acting
what type of H1 antihistamine (generation) can be used to treat motion sickness, but are highly sedative?
describe other features, as well
1st generation H1 antihistamines:
- neutral/hydrophobic at physiological pH
- sedative (because of H1 receptors affecting circadian rhythm in brain, and these can pass BBB) —> can treat insomnia
- anti-emetic (nausea) and anti-itch
- non-specific effects (anti-cholinergic, anti-alpha-adrenergic, anti-serotonin)
- short acting (6-12 hours)
what generation of H1 antihistamines are longer-acting (between 12-24 hours)?
2nd generation H1 antihistamines:
- ionized at physiological pH (don’t cross BBB)
- highly selective
- longer-acting (12-24 hours)
why are 1st generation H1 antihistamines highly sedative, but not 2nd generation?
1st generation are hydrophobic, can cross BBB to reach H1 receptors in brain that control circadian rhythm
therefore, they can be used to treat insomnia
[2nd generation are ionized, cant’ cross BBB]
Diphenhydramine, more commonly known as Benadryl, is a ____ generation ____ antihistamine
Diphenhydramine (Benadryl): 1st generation H1 antihistamine
uses: allergy symptoms, hives, itching, motion sickness, insomnia, certain symptoms of Parkinson’s
side effects (think about general effects/ properties of 1st generation antihistamines and these make sense): drowsiness, dry mouth (anticholinergic), dizziness, others
Benadryl is a ______ type of antihistamine that also goes by the name of ______
Diphenhydramine (Benadryl): 1st generation H1 antihistamine
uses: allergy/cold symptoms, hives, itching, motion sickness, insomnia, symptoms of Parkinson’s
Tripelennamine, more commonly known as PBZ, is a _____ generation ____ antihistamine
Tripelennamine (PBZ): 1st generation H1 antihistamine
uses: allergy/cold symptoms
side effect (typical of 1st gen H1): drowsiness, fatigue, dizziness, dry mouth, difficulty urinating
PBZ, also known as _______, is what kind of antihistamine?
Tripelennamine (PBZ): 1st generation H1 antihistamine
*pbZ gives you the Zzzs, since sleepiness is a side effect. Sleepiness is a typical side effect of 1st gen H1 antihistamines because they can cross BBB (hydrophobic) and bind H1 receptors in brain that mess with circadian rhythm
Chlorpheniramine, branded as Chlor-Trimenton, is a ____ generation _____ antihistamine
Chlorpheniramine (Chlor-Trimenton): 1st generation H1 antihistamine
uses: allergy/cold/flu symptoms
side effects: typical of 1st gen H1 antihistamines (dizziness, drowsiness, dry mouth, blurred vision, others)
Chlor-Trimenton is known by what other name, and what kind of antihistamine is it?
Chlorpheniramine (Chlor-Trimenton): 1st generation H1 antihistamine
uses: allergy/cold/flu symptoms
Promethazine, branded as Phenergan, is a ____ generation ____ antihistamine
Promethazine (Phenergan): 1st generation H1 antihistamine
uses: allergy symptoms, motion sickness, nausea after surgery, sedative
side effects: typical of 1st gen H1 (drowsy, dizzy, double vision, dry mouth)
Phenergan is also known as _____ and is what kind of antihistamine?
Promethazine (Phenergan): 1st generation H1 antihistamine
uses: allergy symptoms, motion sickness, nausea after surgery, sedative
Hydroxyzine (Atarax, Vistaril) and Cyclizine/Meclizine (Marezine, Antivert) are both piperazines (organic chemistry) that function as antihistamines. What kind of antihistamines are they and what are their uses?
Hydroxyzine (Atarax, Vistaril): 1st generation H1 antihistamine
uses: skin allergies - urticaria (hives) or contact dermatitis; sedative for anxiety, anti-nausea
Cyclizine/ Meclizine (Marezine, Antivert): 1st generation H1 antihistamine
uses: nausea, dizziness from motion sickness, vertigo (from diseases affecting inner ear)
both have typical 1st gen H1 antihistamine symptoms
what are the special uses of Hydroxyzine, and what kind of antihistamine is it?
bonus: what brand names does it go by?
Hydroxyzine: 1st generation H1 antihistamine
treats allergic skin reactions - urticaria (hives), contact dermitis
also works as sedative for anxiety, and controls nausea
brand names: Atarax, Vistaril
what are the special uses of Cyclizine/ Meclizine (do the same thing), and what kind of antihistamine is it?
bonus: what brand names do these go by?
Cyclizine/ Meclizine: 1st generation H1 antihistamines
treat nausea from motion sickness, vertigo from diseases affecting inner ear
brand names:
Cyclizine = Marezine
Meclizine = Antivert
Cyproheptadine, branded as Periactin, is a ___ generation ____ antihistamine
Cyproheptadine (Periactin): 1st generation H1 antihistamine
uses: symptoms of allergic reactions
significant anti-serotonin and anti-cholinergic properties
side effects typical for 1st gen H1 antihistamine
Periactin is also known as ____ and is what kind of antihistamine?
what is it used for?
Cyproheptadine (Periactin): 1st generation H1 antihistamine
use: symptoms of allergic reactions
significant anti-serotonin and anti-cholinergic properties
which 1st generation H1 antihistamine can treat some symptoms of Parkinson’s?
Diphenhydramine (Benadryl): treats allergy symptoms, motion sickness, insomnia, symptoms of Parkinson’s
which of these 1st generation H1 antihistamines is used to treat nausea/vomiting or pain after surgery?
a. hydroxyzine
b. cyproheptadine
c. promethazine
d. tripelennamine
Promethazine (Phenergan) - can be used to treat N/V/pain after surgery
also used for allergy symptoms, motion sickness, sedative/sleep aid
*Promethazine treats Pain so Peggy can go to Prom after surgery
which of these 1st generation H1 antihistamines is used to treat allergic skin reactions such as urticaria (hives) or contact dermititis?
a. hydroxyzine
b. cyclizine
c. promethazine
d. tripelennamine
Hydroxyzine (Atarax, Vistaril) - treats allergic skin reactions
can also be used as sedative for anxiety, and treats N/V
*Hal got Hydrogen peroxide on his skin, which caused contact dermititis, so he took Hydroxyzine
which of these 1st generation H1 antihistamines is used to treat nausea/dizziness from motion sickness and vertigo caused by diseases of the inner ear?
a. hydroxyzine
b. cyclizine
c. cyproheptadine
d. diphenhydramine
Cyclizine (Marezine) / Meclizine (Antivert) - treat nausea/dizziness caused by motion sickness and vertigo caused by inner ear diseases
*Cindy went on the Cyclone at the Carnival and got so motion sick that she was dizzy, so she took Cyclizine
which of these 1st generation H1 antihistamines is used to treat symptoms of allergic reaction, such as those caused by seasonal allergies, food, blood or plasma? Note that this antihistamine has significant anti-serotonin and anti-cholinergic properties.
a. hydroxyzine
b. promethazine
c. chlorpheniramine
d. cyproheptadine
Cyproheptadine (Periactin) - treats symptoms of allergic reactions, and has significant anti-serotonin and anti-cholingeric reactions
*Cyprus takes Cyproheptadine in Summer for her seasonal allergies, even though it affects her Serotonin
Certirizine, better known as Zyrtec, is a ____ generation ____ antihistamine
Certirizine (Zyrtec): 2nd generation H1 antihistamine
treats cold/allergy symptoms, itching and swelling caused by urticaria (hives)
*has slight BBB passage (it’s a carboxylated hydroxyzine), so slight symptoms similar to 1st gen (drowsy, dizzy, dry mouth - but not severe)
when formulated with pseudoephedrine HCl (Zyrtec-D*) —> treats insomnia, restlessness, elevated heart rate
what is the other name for Zyrtec, what kind of antihistamine is it, and what does it treat? What about Zyrtec-D?
Cetirizine (Zyrtec): 2nd generation H1 antihistamine
treats allergy/cold symptoms, itching/swelling caused by urticaria
Zyrtec-D (has psuedoephidrine HCl): can treat insomnia, restless, elevated heart rate
*has slight BBB passage
Loratadine, better known as Claritin, is a ___ generation ____ antihistamine
Loratadine (Claritin): 2nd generation H1 antihistamine
treats cold/allergy symptoms, hives/itching in people with chronic skin reactions
*metabolized by hepatic cytochrome p450 (CYP3A4, CYP2D6) into active metabolite —> inhibited by food/drugs that inhibit CYPs (erythromycin, grape fruit juice, etc)
*when formulated with pseudoephedrine HCl (Claritin-D) —> can treat insomnia, restless, elevated heart rate
Claritin is also known as what, and is what kind of antihistamine?
what does it do?
Loratadine (Claritin): 2nd generation H1 antihistamine
treats cold/allergy symptoms, hives/itching in people with chronic skin reactions
Claritin-D (with pseudoephidrine HCl) can treat insomnia, restlessness, elevated heart rate
*metabolized into active form via p450 system (CYP3A4, CYP2D6)
How is Loratadine metabolized? What is the significance of this?
Loratadine (Claritin): 2nd generation H1 antihistamine
metabolized to active form via cytochrome p450 systems (CYP3A4, CYP2D6)
—> so food/drugs that inhibit CYPs (erythromycin, grape fruit juice - furanocoumarin) inhibit action of Loratadine
Fexofenadine, better known as Allegra, is a ___ generation ____ antihistamine
Fexofenadine (Allegra): 2nd generation H1 antihistamine
treats hay fever (seasonal allergies), itching/hives caused by chronic idiopathic urticaria
Allegra-D (with psuedoephidrine HCl) —> treats insomnia, restlessness, elevated heart rate
side effects: N/V, menstrual cramps, headache, muscle pain
Allegra is also called what, and what kind of antihistamine is it? What is it used for? What are the specific side effects?
Fexofenadine (Allegra): 2nd generation H1 antihistamine
treats hay fever (seasonal allergies), itching/hives caused by chronic idiopathic urticaria
Allegra-D can also treat insomnia, restlessness, elevated heart rate (with psuedoephidrine HCl)
side effects: N/V, menstrual cramps, headache, muscle pain
What is different about Zyrtec-D, Claritin-D, and Allegra-D compared to their original formulation?
Give the alternative names for each of these
these forms have pseudoephidrine HCl, and can treat insomnia, restlessness, elevated heart rate
Zyrtec = Cetirizine
Claritin = Loratadine
Allegra = Fexofenadine
Name 3 common 2nd generation H1 antihistamines
(hint: think brand names first, then think of their names)
name the special uses for each (other than cold/allergy symptoms)
Cetirizine (Zyrtec): itching/swelling of urticaria
Loratadine (Claritin): hives/itching in people with chronic skin reactions
Fexofenadine (Allegra): itching/hives caused by chronic idiopathic urticaria
(all treat cold/allergy symptoms, all are available as “___-D” form which additionally treats insomnia, restlessness, elevated heart rate)
Which of these 2nd generation H1 antihistamines can treat skin hives and itching in patients with chronic skin reactions?
a. cetirizine
b. loratadine
c. fexofenadine
b. loratadine (Claritin): can treat chronic skin reaction symptoms
*CYP3A4 and CYP2D6 metabolize into active form
a. certirizine = Zyrtec
c. fexofenadine = Allegra
*Claritin (loratadine) treats Chronic skin reactions
Which of these 2nd generation H1 antihistamines can treat itching and hives caused by chronic idiopathic urticaria?
a. certirizine
b. loratadine
c. fexofenadine
c. fexofenadine (Allegra): can treat chronic idiopathic urticaria
a. certirizine = Zyrtec
b. loratadine = Claritin
Which 2nd generation H1 antihistamine would have decreased effectiveness in a patient who regularly drinks grape fruit juice, which contains furanocoumarin?
Loratadine (Claritin): metabolized by hepatic cytochrome p450 system (CYP3A4, CYP2D6) into active form
Which antihistamine of those below can be given after surgery to treat nausea, vomiting, and pain?
a. meclizine
b. fexofenadine
c. promethazine
d. diphenhydramine
e. tripelennamine
c. promethazine (Phenergan): 1st generation H1 antihistamine, can treat N/V/pain after surgery, also sedative and prevents motion sickness
a. meclizine (Antivert) = cyclizine (Marezine) - 1st gen
b. fexofenadine (Allegra) - 2nd gen
d. diphenhydramine (Benadryl) - 1st gen
e. tripelennamine (PBZ) - 1st gen
*Promethazine treats Pain so Peggy can go to Prom after surgery
Your patient has an inner ear disease that causes her to experience vertigo. She also tends to get very motion sick during car rides to school. While taking her history, she tells you that she takes an antihistamine for these symptoms, but she can’t remember the name. It is most likely:
a. cyclizine
b. chlorpheniramine
c. hydroxyzine
d. cetirizine
e. tripelennamine
a. cyclizine (Marezine), meclizine (Antivert): prevents N/V/dizziness caused by motion sickness, symptoms of vertigo from inner ear disease (1st generation H1 antihistamine)
b. chlorpheniramine (Chlor-Trimeton) - 1st gen
c. hydroxyzine (Atarax, Vistaril) - 1st gen
d. cetirizine (Zyrtec) - 2nd gen
e. tripelennamine (PBZ) - 1st gen
*Cindy went on the Cyclone at the Carnival and got so motion sick that she was dizzy, so she took Cyclizine
Levocetirizine (Xyzal) is a 3rd generation H1 antihistamine that is the active R-enantiomer of ______
Levocetirizine (Xyzal): 3rd gen H1 antihistamine, active R-enantiomer of cetirizine - more potent
remember that cetirizine (Zyrtec) is 2nd gen H1 antihistamine
***levoCETIRIZINE
the R-enantiomer of cetirizine is _____, which is more potent
Levocetirizine (Xyzal): 3rd gen H1 antihistamine
cetirizine (Zyrtec): 2nd gen H1 antihistamine
Desloratadine (Clarinex) is the active/major metabolite of ______
Desloratadine (Clarinex): active/major metabolite Loratadine —> more potent and not affected by CYP inhibitors
loratadine (Claritin): 2nd gen H1 antihistamine, requires CYP metabolism to be active
***desLORATADINE
the active/major metabolite of loratadine is _______, which has greater potency and is not affected by CYP metabolism
desloratadine (Clarinex): 3rd gen H1 antihistamine
loratadine (Claritin): 2nd gen H1 antihistamine
what is the immediate treatment for anaphylaxis?
epinephrine !
*antihistamines are not enough because there are more inflammatory mediators than just histamine
how does overdose of 1st generation H1 antihistamines affect the CNS?
hyperstimulates CNS —> restlessness, tremors, nervousness, anxiety, hallucinations, convulsions
*note that 1st gen H1 antihistamines are metabolized by CYP enzymes, so drugs that inhibit CYP enzymes can induce overdoes (except for Loratadine, which needs to be CYP metabolized to be active)
what kinds of antihistamines are contraindicated for pregnant/nursing women and newborns/young infants?
1st generation H1 antihistamines - hydrophobic, can cross placenta
What kind of antihistamines have anticholinergic (antimuscarinic) effects? Name 3 of these effects
1st generation H1 antihistamines (can cross BBB)
examples: dilated pupils, blurred vision, diplopia, dry eyes, dry mouth
describe the mechanism and use of Cromolyn and Nedocromil
block histamine action by inhibiting mast cell degranulation
(block Cl- channels and subsequent Ca2+ mobilization)
used prophylactically, must be inhaled (inhaler, nasal spray)
used to prevent asthma attacks, especially in children
name 2 drugs that block histamine action by inhibiting mast cell degranulation
what is their specific mechanism?
- Cromolyn
- Nedocromil
stabilize the cell membrane - block Cl- channels and subsequent Ca2+ mobilization (which causes degranulation)
must be inhaled, prevent allergic bronchospasm (inhaler), rhinoconjunctivitis (nasal spray), asthma attacks (esp. children)
epinephrine is a potent, rapid treatment for anaphylaxis, inducing bronchodilation and vasoconstriction
epinephrine is an agonist of _____ receptors
epinephrine: agonist of alpha (—> vasoconstriction) and Beta (—> Bronchodilation) adrenergic receptors
secreted by adrenal medulla
what is the general effect of H2 antihistamines?
decreased gastric acid secretion, vasoconstriction, decreased heart rate
remember that H2 receptors are found on parietal cells, cardiomyocytes, smooth muscle, mast cells, basophils, postsynaptic histaminergic neurons
name 4 H2 antihistamines and indicate which exhibit CYP interference
which is the most potent?
- cimetidine (Tagamet): inhibits multiple cytochrome p450 (CYP) drug metabolism pathways - potential for adverse drug-drug interactions
- ranitidine (Zantac): some CYP interference
- Famotidine (Pepcid): most potent H2 antihistamine
- nizatidine (Tazac, Axid)
*hint: they all end in “-tidine”
*Famous Clementine Ran it Nicely:
Famous = Famotidine
Clementine = Cimetidine
Ran it = Ranitidine
Nicely = Nizatidine
what kind of antihistamines end in “-tidine”?
H2:
Famous Clementine Ran it Nicely:
Famous = Famotidine
Clementine = Cimetidine
Ran it = Ranitidine
Nicely = Nizatidine
which H2 antihistamine inhibits multiple hepatic cytochrome p-450 (CYP) drug metabolism pathways? What is the significance of this?
Cimetidine (Tagamet)
potential for adverse drug-drug interactions
what is the most potent H2 antihistamine?
Famotidine (Pepcid)
One of your patients is experiencing serious adverse drug-drug interactions. A resident tells you they just gave the patient an antihistamine for their heartburn, but didn’t document it and now they forget which one they prescribed (whoops!). The resident most likely gave the patient:
a. Levocetirizine
b. Loratadine
c. Cetirizine
d. Cimetidine
e. Cyproheptadine
f. Hydroxyzine
H2 antihistamines lower gastric acid secretion
*remember that H2 antihistamines end in “-tidine”
d. Cimetidine: H2 antihistamine that inhibits several CYP pathways (adverse drug-drug interactions)
a. Levocetirizine: 3rd gen H1
b. Loratadine (Claritin): 2nd gen H1 (needs to be CYP metabolized to be active)
c. Cetirizine (Zyrtec): 2nd gen H1
e. Cyproheptadine: 1st gen H1
f. Hydroxyzine: 1st gen H1
what kind of antihistamine can treat Zollinger-Ellison syndrome?
Zollinger-Ellison syndrome: caused by hyper-gastrin-secreting tumors of pancreas or duodenum
treat with H2 antihistamines (which treat GERD, gastric/duodenal ulcers, stress-induced gastritis)
Your patient has a tumor in their duodenum that is hyper-gastrin-secreting. What is this syndrome called and what type of antihistamine can you treat them with?
Zollinger-Ellison syndrome: caused by hyper-gastrin-secreting tumors of pancreas or duodenum
treat with H2 antihistamines (which treat GERD, gastric/duodenal ulcers, stress-induced gastritis)
dyspepsia
aka GERD or heart burn
can H2 antihistamines enter the CNS
NO - hydrophilic
also highly specific (do not affect H1 or H3 receptor signaling)
which H2 antihistamines interfere with CYP drug metabolism (2)? How does this effect the half life of other drugs metabolized by these pathways?
Cimetidine, Ranitidine (less so)
potentially increases half life of other drugs
why should you be careful giving an H2 antihistamine to a patient with impaired renal or hepatic function?
which patients does this particularly impact?
can cause neurological effects - confusion, slurred speech, delirium, hallucination, agitation
primarily elderly patients receiving IV administration
Which of these antihistamines is an active R-enantiomer of cetirizine?
a. desloratadine
b. cyproheptadine
c. ranitidine
d. levocetirizine
e. loratadine
f. diphenhydramine
g. nizatidine
d. levocetirizine: 3rd gen H1 antihistamine, more potent than cetirizine (Zyrtec)
a. desloratadine: 3rd gen H1, metabolite of Loratadine
b. cyproheptadine: 1st gen H1
c. ranitidine: H2
e. loratadine: 2nd gen H1
f. diphenhydramine (Benadryl): 1st gen H1
g. nizatidine: H2
which of these antihistamines is the major active metabolite of Loratadine, increasing its potency without influence by CYP inhibitors?
a. desloratadine
b. famotidine
c. promethazine
d. chlorpheniramine
e. tripelennamine
a. desloratadine: 3rd gen H1, metabolite of Loratadine
b. famotidine: H2
c. promethazine: 1st gen H1
d. chlorpheniramine: 1st gen H1
e. tripelennamine: 1st gen H1
which of these antihistamines has significant anti-serotonin and anti-cholinergic properties?
a. hydroxyzine
b. fexofenadine
c. cimetidine
d. desloratadine
e. cyproheptadine
e. cyproheptadine: 1st gen H1, treats symptoms of allergic reactions
a. hydroxyzine: 1st gen H1
b. fexofenadine: 2nd gen H1
c. cimetidine: H2
d. desloratadine: 3rd gen H1 (Loratadine metabolite)
which of these antihistamines treats N/V/pain after surgery?
a. piperazine
b. piperidine
c. promethazine
c. promethazine: 1st gen H1, treats N/V/pain after surgery
[piperazine and piperidine are organic chemistry terms for structures of other antihistamines]
hint: of the antihistamines you have to learn, those ending in “-amine”, “-zine”, and “-tidine” belong to what families, respectively?
“-amine” - 1st gen H1 (diphenhydramine, tripelennamine, chlorpheniramine)
“-zine” - 1st gen H1 (promethazine, hydroxyzine, cyclizine, meclizine)
“-tidine” - H2 (cimetidine, ranitidine, famotidine, nizatidine)
what happens during anaphylactic shock
allergen is distributed systematically, get systemic Type I hypersensitivity
systemic mast cell and basophil degranulation
life-threatening bronchoconstriction and vasodilation which leads to severe drop in bp
laryngeal swelling, angioedema, increased capillary permeability, reflex tachycardia (rapid weak pulse)
