6582348
Description
Flashcards by Andrew Street, updated more than 1 year ago
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Created by Andrew Street
almost 8 years ago
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| Question | Answer |
| Give eg's of & indications for histamine H1-receptor antagonists. | eg's: cyclizine, cinnarizine, promethazine Indications: • Prophylaxis & Rx of N & V, particularly in the context of motion sickness or vertigo |
| MOA of histamine H1-receptor antagonists. | N & V are triggered by a variety of factors, including gut irritation, drugs, motion & vestibular disorders, as well as higher stimuli (sights, smells, emotions). The various pathways converge on a ‘vomiting centre’ in the medulla, which receives inputs from the chemoreceptor trigger zone (CTZ), the solitary tract nucleus (which is innervated by the vagus nerve), the vestibular system & higher neurological centres. Histamine (H1) and acetylcholine (muscarinic) receptors predominate in the vomiting centre & in its communication with the vestibular system. Drugs such as cyclizine block both of these receptors. This makes them useful treatments for N & V in a wide range of conditions (e.g. drug-induced, post-operative, radiotherapy), but most particularly when associated with motion or vertigo. |
| SE's of histamine H1-receptor antagonists. | SE's: • Drowsiness - cyclizine causes the least drowsiness in this class • Dry throat & mouth • Tachycardia (palpitations) after an IV injection • Excitation or depression due to central anticholinergic effects |
| CI's, cautions, & important interactions of histamine H1-receptor antagonists. | CI's: • Avoid in pt's at risk of hepatic encephalopathy due to their sedative effects • Avoid in pt's susceptible to anticholinergic side effects, such as those with prostatic hypertrophy (who may develop urinary retention) Cautions: • See above Important interactions: Sedation may be greater when combined with other sedative drugs (eg benzodiazepines, opioids). Anticholinergic effects may be more pronounced in pt's taking ipratropium or tiotropium. |
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