↓ or prevents histamine effects on smooth muscle, immune cells; blocks muscarinic and α adrenoceptors; highly sedative

Sedation when used in hay fever, muscarinic blockade symptoms, orthostatic hypotension, anticholinergic effects, drowsiness

IgE immediate allergies, especially hay fever, urticarial, sedative, antiemetic ( pregnancy), antimotion sickness drug

slight sedation with fewer autonomic effects

anticholinergic effects, drowsiness

Moderate sedation, also has antiserotonin activity

anticholinergic effects, drowsiness

Potent H₁-receptor-blocking as well as 5-HT₂-blocking actions; prevents smooth muscle effects of both amines;  antimuscarinic effects and sedation

drowsiness

Carcinoid tumor (secrete excessive levels of serotonin) and cold-induced urticarial (hives)

↓ or prevents histamine effects on smooth muscle, immune cells

Sedation and arrhythmias in overdose

IgE immediate allergies, especially hay fever, urticaria

↓ or prevents histamine effects on smooth muscle, immune cells

Sedation and arrhythmias in overdose

IgE immediate allergies, especially hay fever, urticaria

↓ or prevents histamine effects on smooth muscle, immune cells

Sedation and arrhythmias in overdose

IgE immediate allergies, especially hay fever, urticaria

(See CH 62) H₂ receptor antagonist, blocks acid secretion in stomach; ↓ cAMP, ↓ gastric acid secretion, ↓ pepsin/intrinsic factor production

Mental status changes, gynecomastia (men), galactorrhea (women)

Rx: peptic ulcer disease

Prevents: gastroesophageal reflux

disease (GERD), bleeding from stress related gastritis

Inhibit CYP450

Partial agonist at 5-HT_1B/1D receptors; may reduce release of calcitonin gene-related peptide and perivascular edema in cerebral circulation

Paresthesias, dizziness, coronary vasoconstriction

Migraine and cluster headaches

5-HT₃ antagonist; blocks 5-HT₃ in gut and CNS
(See CH 62)

Very low toxicity but may slow colonic transit

Prevention of nausea and vomiting associated with surgery and cancer chemotherapy

Mixed partial agonist effects at 5-HT₂ and α adrenoceptors and CNS dopamine receptors; causes marked smooth muscle contraction but blocks α-agonist vasoconstriction

GI disturbances most common; prolonged vasospasm causing gangrene; uterine spasm; cardiovascular toxicity; ergot poisoning called St. Anthony’s fire

Migraine and cluster headache, pituitary dysfunction (hyperprolactinemia), postpartum hemorrhage

Agonist at dopamine D2 receptors and various serotonin receptors

Vasospasm

Parkinson’s disease, pituitary tumor → hyperprolactinemia