6596813
Description
Flashcards by Andrew Street, updated more than 1 year ago
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Created by Andrew Street
over 7 years ago
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| Question | Answer |
| Give eg's of & indications for phenothiazines. | eg's: prochloperazine, chlopromazine Indications: • N & V - prophylaxis & Rx especially due to vertigo. Due to SE's other antiemetics are usually preferable. • Psychotic disorders - 1st generation (typical) antipsychotics for Rx eg schizophrenia |
| MOA of phenothiazines. | 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 and higher neurological centres. The antiemetic properties of phenothiazines arise from blockade of various receptors, including dopamine (D2) receptors in the CTZ & gut (see Antiemetics, dopamine D2-receptor antagonists) and, to a lesser extent, histamine (H1) & acetylcholine (muscarinic) receptors in the vomiting centre & vestibular system (see Antiemetics, histamine H1-receptor antagonists). This makes them effective for N & V in a wide range of situations, including chemotherapy, radiotherapy & vertigo. |
| SE's of phenothiazines. | • Drowsiness • Postural hypotension • Extrapyramidal syndromes (due to D2 receptor blockade) - in short term Rx most likely to take the form of an acute dystonic reaction such as oculogyric crises. In longer term Rx extrapyramidal syndromes such as tardive dyskinesia may occur. • Prolonged QT-interval |
| CI's, cautions, & important interactions of phenothiazines. | CI's: • Severe liver DS - due to potential for hepatotoxicity • Avoid in pt's susceptible to anticholinergic side effects, such as those with prostatic hypertrophy (may develop urinary retention) Cautions: • Elderly - reduce dose Important interactions: You should consult the BNF when prescribing for a patient taking these drugs as there is an extensive list of interactions. Prominent among these are drugs that prolong the QT interval, such as antipsychotics, amiodarone, ciprofloxacin, macrolides, quinine & SSRIs. |
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