DR.LEAL - DRUGS WITH IMPORTANT ACTIONS ON SMOOTH MUCLES PART1 Flashcards
released when there are allergies, asthma, and rhinitis, thereby antihistamines are
taken.
HISTAMINE
Examples of antihistamines:
Cetirizine,
Loratadine
Hydroxyzine
happy neurotransmitter that affects mood
and sleep
SEROTONIN
Important mediator of immediate allergic (such as urticaria) and inflammatory reactions (Type I hypersensitivity reactions)
HISTAMINE
Role in gastric acid secretion
○ Attachment of histamine to H2 receptors
will promote gastric acid secretion; hence,
H2 blockers are given
○ Example of H2 blockers (antacids):
Famotidine, Cimetidine, Ranitidine
HISTAMINE
anesthetic drug classified under opioids; pain reliever
MORPHINE
neuromuscular blocking agent
TUBOCURARINE (CURARE)
requiring energy and calcium
○ A drug that can release histamine in its bulk form
Compound 48/80
Four Histamine receptors:
○ H1: Smooth muscle, endothelium, brain
○ H2: Gastric mucosa, cardiac muscle, mast
cells, brain
○ H3: Presynaptic autoreceptors and
heteroreceptors: brain, myenteric plexus,
other neurons
○ H4: Eosinophils, neutrophils, CD4 T cells
Smooth muscle, endothelium, brain
H1
Gastric mucosa, cardiac muscle, mast
cells, brain
H2
Presynaptic autoreceptors and
heteroreceptors: brain, myenteric plexus,
other neurons
H3
Eosinophils, neutrophils, CD4 T cells
H4
action of histamine on arterioles and
precapillary sphincters
○ Result: ↓ Blood pressure (Anaphylactic shock)
○ Anaphylactic shock: Allergy + Hypotension
VASODILATION
Intradermal injection of histamine:
characteristic
RED SPOT
EDEMA
FLARE
vasoconstrictor; have smooth
muscle actions opposite to those of histamine (act on different receptors)
EPINEPHRINE
causes vasodilation, consequently lowering blood pressure.
HISTAMINE
a vasoconstrictor, is given to counteract the effects of histamine.
EPINEPHRINE
○ Drugs that inhibit the release of histamine
○ Reduce the degranulation of mast cells that results from immunologic triggering by antigen-IgE interaction
RELEASE INHIBITORS
treatment of asthma
CROMOLYN
NEDOCROMIL
Selective H2-receptor antagonists:
therapy for peptic disease (Ex. antacids -
drugs used for hyperacidity)
Histamine Receptor Antagonists
Thioperamide and Clobenpropit
H3 RECEPTOR ANTAGONIST
ANTIHISTAMINE THAT Can cross the blood-brain barrier → effect
in the central nervous system → Strong
sedative effects
1ST GEN
antihistamine that is Less sedating (reduced distribution into the CNS) treatment of allergic rhinitis and chronic urticaria.
○ Example: Cetirizine
2ndGEN
H1 antagonists
○ First generation antihistamine
SEDATION
Scopolamine, Dimenhydrinate
○ Prevents motion sickness
○ Example: Bonamine® generic name:
meclizine hydrochloride
Antinausea and antiemetic actions
- Significant acute suppressant effects on the extrapyramidal symptoms associated with certain antipsychotic drugs
- Can also be used to sedate the patient
Diphenhydramine
Significant atropine-like effects on peripheral muscarinic
receptors
- During an allergic reaction, the patient can experience drooling. Atropine-like action of antihistamine can cause dry mouth, increased heart rate, etc.
Antimuscarinic actions
○Ethanolamine and Ethylenediamine
- Alpha-receptor-blocking (orthostatic hypotension)
- Used during painful labor of pregnant women. It has localized anesthetic activity and sedative. This can be used to lessen the pain of labor.
Promethazine
Inhibit mast cell release of histamine and some other mediators of inflammation
CETIRIZINE
found in the gastric mucosa. Once histamine is released and attached to the H2 receptors, they promote gastric acid secretion.
H2 RECEPTORS
Medicine used to counteract histamine-2 receptors are:
○ Cimetidine (Prototype)
○ Ranitidine
○ Famotidine
○ Nizatidine