Anti-Histamine Drugs Flashcards
What are 3 other terms for histamine?
Biogenic amine, vasoactive amine, autacoid
Is serotonin a vasoactive amine?
Yes
What does autacoid mean?
“Self-remedy” or local
What are some other examples of autacoids?
Endogenous peptides; prostaglandins; leukotrienes; and cytokines.
It what tissue areas is histamine most highly distributed?
Skin; GI and Nasal Mucosa; Lung; Stomach
What is histamine storage content directly related to in peripheral tissues?
The mast cell content. More mast cells = more stored histamine.
Is histamine stored in mast cells of the central nervous system?
No. The CNS is the notable exception to histamine storage in mast cells.
Aside from mast cells, where else is histamine stored?
In basophils, histaminergic neurons, and enterochromaffin-like cells.
What is the function of the subclass of G-proteins, Gs?
Gs proteins stimulate adenylyl cyclases.
What is the function of the subclass of G-proteins, Gq?
Gq proteins stimulate phospholipase C-beta.
What is the function of the subclass of G-proteins, Gi?
Gi proteins inhibit adenylyl cyclase.
What is the function of the subclass of G-proteins, G12/13?
G12/13 stimulate low molecular weight G protein Rho.
What is the post-receptor mechanism of the H1 receptor?
Increased levels of IP3 and DAG(Gq).
What is the post-receptor mechanism of the H2 receptor?
Increased levels of cAMP(Gs).
True or false: Drugs to block all 4 subtypes of histamine receptors are clinically available.
False. Only drugs for H1 and H2 are clinically available.
Intracellulary, how is histamine stored?
In granules.
What receptor subtype of histamine is involved in sensory nerve endings, stimulating pain and itching?
H1 receptor.
Which histamine receptors are involved in modulating release of acetylcholine, amine, and peptide transmitters?
H1, H2, H3.
True or false: In modulating the release of acetylcholine, amine, and peptide transmitters, the H3 receptor is post-synaptic.
False. The H3 receptor is presynaptic in modulating the release of acetylcholine, amine, and peptide transmitters.
True or false: H1 and H2 receptors are post synaptic in modulating the release of acetylcholine, amine, and peptide transmitters.
True.
Histamine binding to endothelial H1 receptors causes what effect?
Release of NO and subsequent smooth muscle relaxation (vasodilation).
True or false. Binding of histamine to endothelial H1 receptors results in decreased peripheral resistance and lowered systemic blood pressure.
True.
Define chronotropism and give an example of it.
Modification of the rate of a periodic movement, such as the heartbeat, through some external influence.
Define ionotropism and give an example.
A process leading to shortening and/or development of tension in muscle tissues, e.g. increased contractile force of the heart.
True or false: Binding of histamine to H1 receptors on the heart affects atrial-ventricular conductance.
True.
Histamine binding to H1/H2 receptors on smooth muscle results in rapid smooth muscle relaxation.
False. Slow smooth muscle relaxation.
What are examples of histamine’s actions on nonvascular smooth muscle?
Bronchioconstriction (H1) and intestine cramps and diarrhea (H1).
Which histamine receptor is involved in promoting gastric acid secretion?
H2.
What is the effect of histamine binding to H1 receptors in the adrenal medulla and ganglia?
High concentration of histamine causes adrenal medullary discharge (epinephrine, catecholamines, etc)
Which histamine receptor is involved with metabolic effects and what are these effects?
H3. Inhibits food intake; increases energy expenditure; reduces obesity.
What is the “triple response” of an intradermal injection of histamine?
Erythema, wheal, and flare.
Which histamine receptors are involved in the “triple response” of an intradermal injection of histamine?
Mostly H1; but also some H2 and H3.
What effect does histamine have on the exocrine glands of the nasal and respiratory areas?
Binds to H1 and increases production of nasal and bronchial mucus.
What are 4 clinical uses of histamine?
Bronchial hyperreactivity testing; integrity test of sensory nerves; assess ability of stomach to secrete acid; test for pheochromocytoma.
What has replaced histamine in testing stomach acid secretion?
Pentagastrin is now used.
How does epinephrine act as an histamine antagonist?
It quickly reverses histamine’s effects on smooth muscle (treat acute anaphylaxis).
What is cromolyn?
A histamine release inhibitor and mast cell stabilizer.
What is the mechanism of action of cromolyn?
Acts on pulmonary mast cells to 1) Inhibit release of histamine and other autacoids during allergic runs; 2) inhibit the function of cells.
How does suppression via cromolyn work?
Cromolyn blocks membrane chloride channels.
True or false: Cromolyn is not useful for skin allergies.
True, it does not inhibit mast cell degranulation in skin.
True or false: Cromolyn is easily absorbed orally.
False. Cromolyn is poorly absorbed orally.
How is cromolyn administered?
Either as a powder (inhalation), a liquid nasal spray (Nasalcrom). or an ophthalmic solution (Opticrom).
What are the clinical uses of cromolyn?
Prophylactic treatment for bronchial asthma. Also for allergic rhinoconjuctivitis.
How is Cromolyn excreted?
Unchanged in bile and urine.
True or false: Cromolyn is ineffective in reversing asthmatic bronchospasm.
True.
What is nedocromil?
A histamine release inhibitor and mast cell stabilizer.
What is the mechanism of action of nedocromil?
Acts on pulmonary mast cells to inhibit release of histamine and other autacoids during allergic rxns; inhibits the function of cells.
How does suppression via nedocromil work?
Blocks membrane chloride channels.
What are some toxic effects of cromolyn?
Wheezing, bronchospasm. Rarely: laryngeal edema. Nasal solution may cause nasal stinging, burning, and irritation.
How is nedocromil administered?
In aerosol form.
What is the toxicity of nedocromil?
Minor: Throat irritation, cough, mouth dryness, chest tightness, and wheezing.
What is the clinical use of nedocromil?
Prophylactic treatment for bronchial asthma.
True or false: Nedocromil is ineffective in reversing asthmatic bronchospasm.
True.
Adding Nedocromil to a standard dose of inhaled corticosteroid appears to improve what?
It improves the control of asthma.
True or false: Cromolyn is more effective than Nedocromil in reducing bronchospasm caused by exercise or cold air.
False. Nedocromil is more effective at reducing bronchospasm caused by exercise of cold air.
What is the mechanism of action of histamine antagonists?
They occupy receptors on the effector cells completely and reversibly, which stops histamine from initiating a response.
What is the name of the H3 blocker currently still under research?
Clobenpropit.
What are the first generation of H1 blockers derivatives of?
They are derivatives of ethyl amine.
What are the characteristics of H1 receptor blockers?
Strong sedative effects; actions at autonomic receptors.
What class of compounds does diphenhydramine belong to?
Ethanol amines
What class of compounds does Chlorpheniramine belong to?
Alkylamines
What class of compounds does Promethazine belong to?
Ethylene diamines.
True or false: Alkylamines has slight sedation.
True.
True or false; Ethanolamines have marked sedation.
True.
What is a common component of OTC cold medication?
Chlorpheniramine (an alkylamine)
True or false: Promethazine is used as a pre-operative drug.
True.
Pyrilamine
An ethylaminediamine. Moderate sedation. Present in OTC sleep aids.
Hydroxyzine
A piperzine derivative. Moderate sedation.
Cyproheptadine.
Moderate sedation; anti-serotonin activity.
