Ondansetron

• 5-HT₃ receptor blocker

  • minimal effects on dopamine, histamine, adrenergic or cholinergic receptor activity

• very effective for prevention of nausea and vomiting caused by chemotherapy or surgery. -- major role in management of severe nausea and vomiting due to anticancer drugs

• Clinical Use:

  • Dosage: 4-8 mg IV (administered over 2-5 minutes just before anesthesia induction)

  • Highly effective in reducing postoperative nausea/vomiting incidents -- particularly in susceptible patient groups:

    • ambulatory gynecologic surgery

    • middle ear surgery

  • Oral or IV reduces incidence of postoperative vomiting and preadolescent children undergoing:

    • ambulatory surgery, e.g. tonsillectomy, strabismus surgery

  • Ondansetron: effective both for prophylaxis and treatment of postoperative nausea/vomiting

    • decreases incidents & intensity of postoperative nausea & vomiting -- but does not totally eliminate this problem

    •  Major advance: reduced side effects compared to previously used antiemetic drugs such as:

      • phenothiazines, antihistamines, butyrophenones

  • Propofol for induction and maintenance of anesthesia may be as effective as ondansetron in reducing/preventing postoperative nausea & vomiting

• Side Effects:

  • Surgical patients:

    • 3% increased liver transaminase enzyme levels

    • 3% headache

  • No sedation, hypotension, dysphoria, extrapyramidal reactions -- side effects associated with other antiemetic drugs

Tropisetron:

• 5-HT₃ receptor blocker

• Effective in managing symptoms induced by carcinoid syndrome-- also some gastrokinetic characteristics

• Effective in preventing chemotherapy/radiotherapy-induced emesis

• Effective in preventing postoperative nausea/vomiting when administered before general anesthetic induction

Granisetron

• More selective 5-HT₃ receptor blocker compared to ondansetron

•  Clinical Use:

  • Effective in the chemotherapy-induced emesis prevention

  • Effective in preventing postoperative nausea/vomiting

• Elimination half-life: nine hours, compared to about three hours for ondansetron: suggesting less frequent dosing with granisetron.

• Significantly higher cost-- could limit clinical use

Dolasetron:

• Highly potent/selective 5-HT₃ receptor blocker

•  Clinical Use:

  • Effective in preventing chemotherapy-induced nausea/vomiting

  • Effective in reducing likelihood of postoperative nausea & vomiting

  • Antiemetic effect due to long-acting, active metabolite (hydrodolasetron; elimination half-life = approximately 8 hours)