AntiHistamines Flashcards
1st. generation H1 blockers EXAMPLES
PROMETHZIAZINE MECLIZINE CLEMASTINE CYCLIZINE HYDROXYZINE Diphenhydramine Dimenhydrinate Chlorpheniramine
PROMETHZIAZINE MECLIZINE CLEMASTINE CYCLIZINE HYDROXYZINE
USE
Allergies insomnia antiemetic anti nausea ● Hay fever ● Angioedema ● Motion sickness ● OTC sleep aid ● Dystonias
PROMETHZIAZINE MECLIZINE CLEMASTINE CYCLIZINE HYDROXYZINE
MOA
Competitive pharmacological block of Peripheral and CNS H1 receptors plus alpha and muscarinic block
● Causes anti motion sickness effect
● Most of these compounds do not influence the formation or release of histamine.
● they block the receptor-mediated response of a target tissue
● These agents have additional effects unrelated to their ability to block H1 receptors.
● These effects reflect binding of the H1-receptor antagonists to cholinergic, adrenergic, or serotonin receptors
blocks H1 receptors
+cholinergic
+alpha-adrenergic
+serotonin
PROMETHZIAZINE MECLIZINE CLEMASTINE CYCLIZINE HYDROXYZINE
Side Effects
● Autonomic block ● Rare CNS excitation ● Hallucinations ● Excitations ● Ataxia Allergic & Inflammatory reactions Allergic rhinitis Urticaria (Eg. RED MAN SYNDROME Vancomycin) Angioedema Contact dermatitis To induce sedation (somnifacient) (1st gen only) Motion sickness & Nausea (taken before symptoms arise) Pruritus & anaphylactic shock Sedation hypotension tachycardia incr. apetite ABCDs
PROMETHZIAZINE MECLIZINE CLEMASTINE CYCLIZINE HYDROXYZINE
Contraindications
Severe HF
Asthma
2nd. gen, H1. blockers
EXAMPLE
CETRIZINE LORATIDINE KETOIFEN DESLORATIDINE Fexofenadine
CETRIZINE
LORATIDINE
KETOIFEN
DESLORATIDINE
USE
● Hay fever
● Angioedema
allergies
CETRIZINE
LORATIDINE
KETOIFEN
DESLORATIDINE
MOA
Competitive pharmacological block of Peripheral H1 receptors
● No automatic or anti motion sickness effect
● Most of these compounds do not influence the formation or release of histamine.
● they block the receptor-mediated response of a target tissue
● These agents have additional effects unrelated to their ability to block H1 receptors.
● These effects reflect binding of the H1-receptor antagonists to cholinergic, adrenergic, or
serotonin receptors
blocks H1, higher selectivity
CETRIZINE
LORATIDINE
KETOIFEN
DESLORATIDINE
SIDE EFFECTS
● Minimal toxicities compared to gen 1
● Acute poisoning due to overdose
● Sedation
● Autonomic block
● Rare CNS excitation
● Hallucinations
● Excitations
● Ataxia
● Polymorphic ventricular tachycardia (cardiovascular effect)
Allergic & Inflammatory reactions
Allergic rhinitis
Urticaria (Eg. RED MAN SYNDROME Vancomycin) Angioedema
Contact dermatitis
To induce sedation (somnifacient) (1st gen only)
Motion sickness & Nausea (taken before symptoms arise) Pruritus & anaphylactic shock
Headaches
Decreased hepatic metabolism of certain drugs like warfarin
CETRIZINE
LORATIDINE
KETOIFEN
DESLORATIDINE
CONTRAINDICATIONS
Glaucoma
Liver problems
Decreased kidney function
Polymorphic ventricular tachycardia
H2 blockers/antagonists
EXAMPLES
CIMETIDINE
RANITIDINE
FAMOTIDINE
NIZATIDINE
CIMETIDINE
RANITIDINE
FAMOTIDINE
NIZATIDINE
USE
GERD,
gastritis,
peptic ulcers
Heartburn
CIMETIDINE
RANITIDINE
FAMOTIDINE
NIZATIDINE
MOA
● Competitive pharmacological block
● No H1, autonomic or anti motion effects
● block the actions of histamine at all H2 receptors
● inhibits of gastric acid secretion
● Inhibition of H2 → ↓ cAMP → ↓ gastric acid secretion
decreases activity of K/H pump, decreasing acid secretion by blocking H2 receptor in parietal cells
CIMETIDINE
RANITIDINE
FAMOTIDINE
NIZATIDINE
SIDE EFFECTS
Drug interactions ● → inhibition of Cyt P450 which causes inhibitions of all other drugs. ● · Loss of appetite Generally well tolerated Headache common Cimetidine can cause drug interaction ● Gynecomastia -Galactorrhea (androgenic and prolactin effect) ● · ↓ creatinine secretion ● · ↓libido Headaches Gynecomastia galactorrhea
CIMETIDINE
RANITIDINE
FAMOTIDINE
NIZATIDINE
CONTRAINDICATIONS
Stomach cancers
Chronic kidney disease (worse than moderate)
