GI: ANTIEMETICS - PHENOTHIAZINES

Question 1

ANTIEMETICS PHENOTHIAZINE: INDICATIONS

Answer 1

• Prophylaxis and Tx of Nausea and Vomiting - particularly when due to vertigo
• Psychotic disorders (eg Schizophrenia) - 1st gen Antipsychotics

Question 2

ANTIEMETICS PHENOTHIAZINE: MOA

Answer 2

• Blockade of various receptors (D2 in the CTZ and gut), lesser extent H1 and Ach (Muscarinic) receptors in the vomiting and vestibular system
• Effective for nausea and vomiting in a variety of settings (eg chemo, radio therapy, vertigo)

Question 3

ANTIEMETICS PHENOTHIAZINE: ADVERSE EFFECTS

Answer 3

• Drowsiness and postural hypertension
• Movement abnormalities (eg EXTRAPYRAMIDAL SYNDROMES - arising from D1 receptor blockade)
• Acute dystonic rxn (such as an oculogyric crisis) - ST
• Extrapyramidal syndromes (TARDIVE DYSKINESIA)
• QT-interval prolongation

Question 4

ANTIEMETICS PHENOTHIAZINE: WARNINGS

Answer 4

• Sedative effect
• Potential for hepatotoxicity -> avoided in severe liver dx patients
• Avoided in patients susceptible to anticholinergic SEs - PROSTATIC HYPERTROPHY ( who may develop urinary rtn)
• Reduced doses in the elderley

Question 5

ANTIEMETICS PHENOTHIAZINE: INTERACTIONS

Answer 5

• Extensive list of interactions, consult the BNF

- Drugs that prolong QT interval (eg antipsychotics, amiodarone, ciprofloxacin, maroclides, quinine, SSRIs)

Question 6

ANTIEMETICS PHENOTHIAZINE: EXAMPLES

Answer 6

• Prochlorperazine

- Chloropromazine