title: No more than necessary: safety and efficacy of low-dose promethazine.
abstract: BACKGROUND
  Limitations in antiemetic options have resulted in increased use of intravenous promethazine. However, this drug has significant sedative effects with its standard dosage of 25 mg, especially when used in conjunction with narcotic analgesics. While studies have revealed the bioavailability of enteric promethazine to be 25%, current dosing references suggest identical dosing regardless of the route of administration.
  
  
  OBJECTIVE
  To compare the antiemetic efficacy and sedative effects of low-dose intravenous promethazine (6.25 or 12.5 mg) with intravenous ondansetron 4 mg.
  
  
  METHODS
  We assessed inpatients with noncritical conditions at Anne Arundel Medical Center who were treated for nausea or vomiting from any cause except chemotherapy or pregnancy. Forty-six patients received low-dose promethazine and 41 received ondansetron. Statistical analysis was carried out for significant differences in efficacy and sedation.
  
  
  RESULTS
  For patients who received intravenous promethazine 6.25 or 12.5 mg, nausea and vomiting were relieved at one hour in 74% and 68%, respectively, compared with 59% for intravenous ondansetron 4 mg. Results at 3 hours were 67% and 80% for promethazine and 71% for ondansetron. Median sedation scores at one hour were equal at 3 for promethazine and ondansetron (4 = fully awake); at 3 hours, the median scores were 4 and 3.5, respectively. There were no statistically significant differences among any of these results.
  
  
  CONCLUSIONS
  Low-dose (6.25 mg) intravenous promethazine relieves nausea and vomiting as effectively as intravenous ondansetron 4 mg.
authors.affiliation: Anne Arundel Medical Center, Annapolis, MD 21401-3019, USA. jdmoser@aahs.org
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Moser
authors.forename: James B
authors.initials: JB
authors.lastname: Caldwell
authors.forename: F Jane
authors.initials: FJ
authors.lastname: Rhule
mesh_terms: D000932:Antiemetics / Q000008:administration & dosage / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D009325:Nausea / Q000188:drug therapy*; D017294:Ondansetron / Q000008:administration & dosage / Q000627:therapeutic use*; D011398:Promethazine / Q000008:administration & dosage / Q000627:therapeutic use*; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D014839:Vomiting / Q000188:drug therapy*
chemical_list: D000932:Antiemetics; D017294:Ondansetron; D011398:Promethazine