Immunopharm - Antihistamines and Migraines Flashcards
A migraine is a ___ headache. The inflammatory response spreads along the ___ system and arrives in the ___ ___ ___ and other areas to convey pain.
A migraine is a neurovascular headache. The inflammatory response spreads along the trigeminovascular system and arrives in the trigeminal nucleus caudalis and other areas to convey pain
Histamine:
Derived from ___ of ___, catalyzed by L-___ ____. Once formed it is stored or inactivated by ___-N-____ (in the CNS) or diamine oxidase (resulting in ____)
Histamine:
Derived from decarboxylation of histidine catalyzed by L-_histidine decarboxylase_. Once formed, it is stored or inactivated by histamine-N-_methyltransferase_ (in the CNS) or diamine oxidase (resulting in deamination)
Histamine:
- Where is it stored? Speed of turnover?
- Where does it have rapid turnover?
Histamine:
- Stored in mast cells and basophils with slow turnover
- Rapid turnover in neurons and enterochromaffin-like cells in the gastric mucosa
Histamine:
The allergen stimulates __ cells to produce ___ antibodies that then bind to ___ receptors on mast cells and basophils. This causes _____ and further allergen binding causes ___ of __/___ receptors producing degranulation (____ release)
Histamine:
The allergen stimulates B cells to produce IgE antibodies that then bind to Fc receptors on mast cells and basophils. This causes sensitization and further allergen binding causes crosslinking of IgE/Fc receptors producing degranulation (histamine release)
Function of Histamine:
- ____ responses: rhinitis and ___ (hives)
- 4 cardiovascular effects?
- What does it do to the airways?
Function of Histamine:
- Allergic response: rhinitis and urticaria
- CV: vasodilation, increased vascular permeability, injection produces a triple response (red spot/flare/wheal), and increase force of contraction of the heart
- Causes bronchoconstriction
Function of Histamine:
- Increases ___ ___ secretion
- Causes itch and potential ____ (severe hypotension, bronchoconstriction, and ____ swelling)
Function of Histamine:
- Increases gastric acid secretion
- Causes itch and potential anaphylaxis (severe hypotension, bronchoconstriction, and epiglottal swelling)
Histamine receptors:
H1:
- Distribution?
- Function?
Function of Histamine:
H1:
- In smooth muscle, vascular endothelium, and brain
- Bronchoconstriction, separation of endothelial cells (hives), pain, and itching
Histamine Receptors:
H2:
- Distribution?
- Function?
Histamine Receptors:
H2:
- Gastric mucosa, cardiac muscle, and brain
- vasodilation and stimulation of gastric acid secretion
Histamine Receptors:
H3:
- Distribution?
- Function?
Histamine Receptors:
H3:
- CNS and some PNS (autoreceptor in the PNS)
- Decreases NT release: histamine, ACh, NE, 5-HT
Histamine Receptors:
- All receptor subtyptes are ___ ____ ___.
- H1 receptors activate __ ___ that convert ____ to IP3 and ___ and are primarily involved in ___ and ___.
Histamine Receptors:
- All receptor subtypes are G protein couples
- H1 receptors activate G proteins that convert phosphatidylinositol to IP3 and DAG and are primarily involved in inflammation and allergy
Histamine Receptors:
- H2 receptors linked through G proteins to increase ___ with its primary function to regulate ___ ___ ___.
- H3 receptors function as ____ ____ in the CNS and PNS
Histamine Receptors:
- H2 increase cAMP and regulate gastric acid secretion
- Function as feedback inhibitors
3 strategies to inhibit histamine’s actions?
a. Administer drugs to counter pathology (Ep for aniphylaxis)
b. Prevent mast cell degeneration - cromolyn
c. Use Histamine receptor antagonists
H1 receptor antagonists:
- All agents are ___, ___, inhibitors.
- They all ___ the effects at H1 receptors and thus are useful in treating?
- What are the NOT effective in treating?
H1 receptor antagonists:
- All agents are reversible, competitive, inhibitors
- They all attenuate the effects at H1 and are good for allergic reactions, rhinitis, urticaria, itch, and flare
- DRUGS NOT EFFECTIVE FOR BRONCHOCONSTRICTION
H1 receptor antagonists:
First vs. Second generation Antagonists:
- First generation are highly ___ soluble and distribute to the ___ whereas second do not.
- First generation drugs produce ___ and ___ and exhibit some anti-_____ activity. Second generation in comparison?
H1 receptor antagonists:
First vs. Second generation Antagonists:
- First generation are highly lipid soluble and distribute to the CNS whereas second do not
- First generation drugs produce drowsiness and sedation and exhibit some anti-_muscarinic_ activity. Second generation has no anti-muscarinic activity and much less drowsiness/sedation
H1 receptor antagonists:
First vs. Second generation Antagonists:
- Why dont second generation drugs readily penetrate the CNS?
- Example of a girst generation drug with anti-muscarinic activity? Uses?
H1 receptor antagonists:
First vs. Second generation Antagonists:
- Dont penetrate because they are ionized at pH=7.4 and they are highly bound to albumin
- 1st generation: meclozine –> antiemetic or some antiparkinsons
First generation H1 receptor Antagonists:
- 5 drugs?
- Absorption? Distribution? Metabolization?
First generation H1 receptor Antagonists:
- Diphenhydramine, chorphenamine, dimenhydrinate, hydroxyzine, and promethazine
- Well absorbed, widely distributed (even to CNS), and extensively metabolized
First generation H1 receptor Antagonists:
- The major side effect? Which drug thus is best and why?
- What are the anticholinergic SE?
- Other SE?
First generation H1 receptor Antagonists:
- Major SE: sedation - chlorphenamin is best because its the least sedating
- Anticholinergic SE: dry mouth, cough, urinary retention, and blurred vision
- Other SE: loss of appetitie, N/V, dizziness, fatigue, tremor, hypersensitivity reactions
First generation H1 receptor Antagonists:
Dimenhydrinate and diphenhydramine have a ___ therapeutic index and often are used ____ as OTC ____.
First generation H1 receptor Antagonists:
Dimenhydrinate and diphenhydramine have a low therapeutic index and are often used recreationally as OTC hallucinogens
Second Generation H1 Receptor Antagonists:
- Drugs?
- Absorption? Distribution? Metabolism?
- SE?
Second Generation H1 Receptor Antagonists:
- Cetirizine, loratedine, desloratadine, and fexofenadine
- Well absorbed; no distribution to CNS; CYP450
- Minimal SE: sedation/drowsiness –> no anticholinergic effects
Therapeutic Actions of Antihistamines:
- Acute ____ reactions
- Reduce ___
- Diminish symptoms of ___ and ___
- What first generation drugs are used for prophylaxis and treatment of motion sickness?
Therapeutic Actions of Antihistamines:
- Acute allergic reactions
- Reduce itching
- Diminish symptoms of cold and flu
- Motion sickness: diphenhydramine and promethazine
Therapeutic Actions of Antihistamines:
- What can diphenhydramine reduce?
- What can promethazine treat?
- First generation drugs are used for ___ and occassionally for ___ but routine use is not recommended.
Therapeutic Actions of Antihistamines:
- Diphenhydramine can reduce Parkinson’s symptoms
- Promethazine can treat nausea and vomitting
- 1st generation: somnolence and occasionally insomnia but shouldnt be used long term
H2 receptor antagonists:
- Drugs?
- Function?
H2 receptor antagonists:
- Cimetidine, famotidine, ranitidine, and nizatidine
- Inhibits stomach acid production
H2 receptor antagonists:
- Indicatons?
- Why is cimetidine no longer recommended?
Therapeutic Actions of Antihistamines:
- Indications: GERD, peptic ulcer disease, and heartburn
- Cimetidine: no longer recommended because it is used as a suicide substrate for CYP 3A4 and potential toxicity of concurrently ingested drugs that are metabolized by this CYP isoform