Term
|
Definition
| mediator of: physiologic response to tissue or cellular injury, inflammatory responses & allergic reactions, cell growth & repair, gastric acid secretion, a neurotransmitter in CNS, & possible regulator of cardiac functions |
|
|
Term
|
Definition
| stored primarily in mast cells & to a lesser extent basophils; found in highest concentrations in skin & mucosa of GI and bronchial tracts; stored in granules, loosely bound to proteoglycans |
|
|
Term
| Mechanisms of Histamine release |
|
Definition
| 1) drug/chemical induced release (displacement by amine drugs, toxins, & venoms); in response to cell or tissue damage; immunologic stimulation (when exposed to appropriate allergen on IgE Abs on mast cells); neuronal & endocrine stimulation (gastric mucosa stimulated by vagal nerve or gastrin) |
|
|
Term
| Physiological Effects of histamine |
|
Definition
| dilates small blood vessels --> flushing, lowered peripheral resistance, fall in BP; increase in capillary permeability --> edema; stimulates peripheral nerve endings --> pain, burning, & itching sensations; "Triple Response" ---> red spot, flare, wheal; Shock --> given in large doses causes anaphylaxis; bronchial constriction; stimulates gastic acid secretion in parietal cells; intense dilation of cerebral vessels; direct effects on heart --> increased force of contraction, slowing of AV conduction |
|
|
Term
|
Definition
| located primarily in skin, BVs, heart, airway, & CNS; mediates rapid vasodilation, increased capillary permeability, irritation of peripheral nerve endings, & bronchoconstriction |
|
|
Term
|
Definition
| located primarily in GI tract, heart, brain, & on various blood vessels; mediates gastric acid secretion; |
|
|
Term
| Therapeutic Uses of Histamine |
|
Definition
| little value in this area; sometimes used in diagnostic tests for allergies, asthma, & for sensory nerve fcn |
|
|
Term
| Pharmacological Effects of H1-histamine antagonists |
|
Definition
| occupy H1 receptor sites as competitive antagonists; Reduce severity of histamine-stimulated: pain, itch, flare response, vasodilation, increase in vascular permeability, & congestion; they DO NOT prevent release of histamine and DO NOT reverse anaphylactic bronchospasm |
|
|
Term
| Therapeutic Uses of H1 Antihistamines |
|
Definition
| treatment of allergies, treatment of common cold, used as antiemetic, sedatives and sleep aids, antisecretory agents, and treatment of Parkinsons disease |
|
|
Term
| Side Effects & Toxicities of H1-Antihistamines |
|
Definition
| Anticholinergic - dry mouth, dry, hot, skin, constipation, urine retention, loss of visual accomodation; sedation, drowsiness, confusion, amnesia, behavioral disturbances; paradoxical CNS stimulation in children; allergic rxns (topical use); lowering of seizure threshold; |
|
|
Term
| Acute poisoning-overdose of H1-Antihistamines |
|
Definition
| Symptoms: excitation, hallucinations, ataxia, incoordination, convulsion, muscular tremors, uncontrollable clonic/tonic jerky motions, fixed dilated pupils, flushed face, fever, coma, cardio-respiratory collapse, death; treat with cholinesterase inhibitors like physostigmine |
|
|
Term
| Drug interactions with H1-Antihistamines |
|
Definition
| potentiation of effects of CNS depressants, alcohol, barbiturates, opioids, benzodiazepines; VERY SERIOUS INTERACTION: with terfenadine or astemizole in conjuction with erythromycin, ketoconazole, or itraconazole --> life threatening arrhythmias (torsades de pointes) due to inhibition of CYP3A4 & subsequent increase in terfenadine & astemizole which block K channels in heart causing serious arrhythmias |
|
|
Term
| Very Sedating H1-Antihistamines |
|
Definition
| doxylamine [Unisom], promethazine HCl [Phenergan], hydroxyzine [Atarax, Vistaril] |
|
|
Term
| Sedating H1-Antihistamines |
|
Definition
| diphenhydramine [Benadryl], dimenhydrinate [Dramamine], brompheniramate maleate [Comtrex, Dimetapp], chlorpheniramine [Chlor-Trimeton], meclizine [Bonine] |
|
|
Term
| Newer, non-sedating H1-Antihistamines |
|
Definition
| loratidine [Claritin, Alavert]/desloratidine [Clarinex], certirizine [Zyrtex], fexofenadine [Allegra] |
|
|
Term
|
Definition
| cimetidine [Tagamet], ranitidine [Zantac], famotidine [Pepcid], nizatidine [Axid] |
|
|
Term
| Pharmacological Effects of H2-Antihistamines |
|
Definition
| inhibition of gastric acid secretion - reduce amount of acid secreted in response to: vagal stimulation, gastrin secretion, stress; |
|
|
Term
| Therapeutic Uses of H2-Antihistamines |
|
Definition
| duodenal & gastric ulcers, gastroesophageal reflux, Zollinger-Ellison syndrome, preoperatively to lessen aspiration damage; prevention of stress ulcers |
|
|
Term
| Side Effects of H2-Antihistamines |
|
Definition
| HA, dizziness, nausea, myalgia, skin rashes, itching; |
|
|
Term
| Side Effects of Cimetidine [Tagament] |
|
Definition
| antiandrogen effect, can cause gynecomastia, decreased libido, & sexual dysfunction in men; sometimes used to treat masculinization (hirsutism) in females; it can intefere with metabolism of other drugs metabolized by cytochrome P450 enzymes |
|
|
Term
| Drug Interactions with Cimetidine |
|
Definition
| potentiates or prolongs actions of drugs metabolized by liver (warfarin, phenytoin, theophylline, phenobarbital, many benzodiazepines, propanolol, nifedipine, digoxin, quinidine, tricyclic antidepressants) |
|
|
