Histamine and Serotonin (pharmacology) Flashcards
What is histamine?
It is a biogenic monoamine autacoids, which is found in non-neural tissues and functions as a neurotransmitter.
What are the major histamine-producing cells? (4)
Mast cells, basophils, ECL cells and histaminergic neuron.
What activates the release of histamine? (4)
-IgE crosslinking
-allergy inducing drugs
-somatostatin
-dopamine d2
From which amino acid is histamine derived from?
Histidine
What type of amino acid is histidine?
Essentially amino acid
Which enzyme catalyzes the formation of histamine from histidine?
Histamine decarboxylase enzyme
What are the characteristics of H1 receptor (histamine receotor)
LOCATION-Throughout the body, skin, CNS, heart, nerve cells.
TYPE OF RECEPTOR- G-protein coupled receptor, activates phospholipase C.
EFFECTS- Increases vascular permeability.
TREATMENT- Nausea, allergies, sleep disorder.
What are the characteristics of H2 receptor?
LOCATION-Throughout the body, gastric mucosa parietal cells, heart.
TYPE OF RECEPTOR- G-protein coupled receptor, it activates adenyl cyclase.
EFFECTS- Increases secretion of gastric acid.
TREATMENT- Stomach ulcers
Clinical relevance of antihistamines (4)
Relief from allergies and immune reactions.
Relief from gastric distress
Relief from certain nausea and vomiting conditions
Used to treat insomnia
Side effects of 1st generation H1 antihistamines (4)
Anticholinergic, antiadrenergic and antiserotonin.
-They can cross the BBB and causes sedation.
-Increased appetite
-Cognitive impairment
What are the H1 antihistamines correctly called?
H1 receptor inverse agonists
What are the differences between first generation and second generation H1 antihistamines? (8)
First genaration
-Lipophilic
-Crosses BBB easily
-Less selective for H1 receptor
-Anticholinergic, antiadrenergic, antisorotonergic and antidopaminergic.
Second generation
-Lipophobic
-Does not cross BBB easily, affects CNS less.
-More selective for H1 receptor
-Less effect on other receptors
Name two first generation antihistamines, what they are used for as well as a special note regarding them (6)
Promethazine
-Used as sedative anti-emetic
-Special note:It is sedative and has anti-emetic effect due to CNS effects.
Cyproheptadine
-Eroxigenic (appetite stimulant)
-Special note: It has eroxigenic effects due to antiserotonergic activity.
Name two second generation antihistamines, what they are used for and a special note about them.
Desloratadine
-Allergies
-Active metabolite of loratadine.
Terfenadine
-Allergies
-Withdrawn due to cardiotoxicity.
Name three receptors that histamine can bind in and the effects it causes.
Alpha 1- smooth muscle contraction
Alpha 2-Smooth muscle relaxation
-Inhibition of transmitter release
Beta -Smooth muscle relaxation
-Heart muscle contraction
-Glycogenolysis
What are the side effects for antihistamines?
CNS effects-Causes sedation, drowsiness and loss of coordination.
Anticholinergic effects- causes tachycardia, dry mouth and urinary retention.
Anti-alpha-adrenergic effects- hypotension leading to dizziness.
Antiserotonergic effects- causes orexigenesis which can lead to weight gain.
Name the two mast cell stabilisers that are used for asthma
Cromoglicic acid
Nedocromil
Name the four H2 receptor antagonists, what they are used as and special notes regarding them
Cimetidine- they have severe side effects.
Nizatidine
Ranitidine
Famotidine
The last three are more potent that cimetidine.
-They are all used as antacid in gastric distress
What are the clinical indications for H2 receptor blockers? (5)
-Duodenal and gastric ulcer disease.
-Stress ulcer and gastritis
-Ellison syndrome
-Gastroesophageal reflux disease (GERD)
-Prophylaxis of aspiration pneumonia
What are some of the side effects of H2 receptor antagonists? (4)
GIT upset
Dizziness
Repetitive use causes low efficacy
Confusion
What is anaphylaxis?
Acute and severe hypersensitivity reaction
Symptoms of anaphylaxis
Immune reactions-rashes, oedema
Respiratory distress-Bronchospasms
Cardiovascular distress-hypotension, arrhythmias
What is the 1st line of treatment for anaphylaxis?
Adrenaline
What are other pharmacological treatments for anaphylaxis
-Bronchodilators
-Adrenocorticosteroids
-Antihistamines
Where do we find serotonin?
-Throughout the body
-Gastrointestinal wall
-Blood
-CNS
How do we get serotonin in the CNS?
-Serotonin cannot cross the BBB, but Tryptophan which forms serotonin can cross the BBB.
Which enzyme degrades serotonin?
Monoamine oxidase A
What are the biological effects of serotonin? (4)
-Nausea and vomiting
-Smooth muscle contraction
-Vasodilation and vasoconstriction blood vessels.
-Inhibition of neurotransmitter release
What do high levels of serotonin cause? (5)
-Migraine
-Diarrhoea
-Seizures
-Fever
-Unconsciousness
What are the treatments for serotonin syndrome?
Cyproheptadine
Anticonvulsants
Muscle relaxants
