antihistamines

What is histamine primarily generated by in the body?

Histamine is mostly generated in mast cells.

What are the major functions of histamine?

Histamine mediates allergic and inflammatory reactions, gastric acid secretion, and neurotransmission in the brain.

What is the primary use of antihistamines?

Antihistamines inhibit the action of histamine and have important therapeutic applications.

Where is histamine predominantly found in the body?

Histamine is found in practically all tissues, especially in the lungs, skin, blood vessels, and GI tract.

Which enzyme is responsible for the synthesis of histamine?

Histamine is synthesized by the enzyme histidine decarboxylase from the amino acid histidine.

What are the stimuli that can trigger the release of histamine?

Stimuli include cell destruction from cold, toxins, insect venoms, and trauma.

What types of receptors does histamine bind to exert its effects?

Histamine binds to H1, H2, H3, and H4 receptors.

What are the differences between first-generation and second-generation H1-receptor blockers?

First-generation drugs may cause sedation and penetrate the CNS, while second-generation agents are less sedating and do not penetrate the blood-brain barrier.

What are common therapeutic uses of H1-receptor blockers?

They are used to treat allergic reactions, allergic rhinitis, urticaria, nausea and motion sickness.

What is the role of epinephrine in treating anaphylaxis?

Epinephrine reverses the effects of histamine and acts via β2 receptors to cause relaxation of smooth muscles.

What is the most frequent adverse reaction associated with first-generation H1 antihistamines?

Sedation is the most commonly observed adverse reaction.

What are some common side effects of first-generation H1 antihistamines?

Common side effects include sedation, dizziness, dry mouth, and urinary retention.

How long does it typically take for H1-receptor blockers to reach maximum serum levels after oral ingestion?

Maximum serum levels usually occur within 1 to 2 hours.

List the four H2-receptor blockers mentioned in the notes.

Cimetidine, ranitidine, famotidine, and nizatidine.

What is a common adverse effect of second-generation antihistamines?

The most common adverse reaction associated with second-generation antihistamines is headache.

Histamine is primarily generated in __________.

mast cells.

The major functions of histamine include mediating __________ and inflammatory reactions.

allergic.

Antihistamines are used to __________ the action of histamine.

inhibit.

Histamine is predominantly found in the lungs, skin, blood vessels, and __________.

GI tract.

The enzyme that synthesizes histamine is called __________ decarboxylase.

histidine.

Histamine release can be triggered by __________ from toxins, insect venoms, and trauma.

cell destruction.

Histamine binds to H1, H2, H3, and __________ receptors.

H4.

First-generation H1-receptor blockers may cause __________ due to CNS penetration.

sedation.

Therapeutic uses of H1-receptor blockers include treating allergic reactions and __________ sickness.

motion.

The adverse reaction most frequently associated with second-generation antihistamines is __________.

headache.