Nalbuphine

PHOENIX,. ARIZ. -- Ondansetron has a dose-related prophylactic effect in relieving pruritus associated with spinal opioids administered for labor analgesia, Dr. Scott Segal said.

Patients who received 8 mg of ondansetron intravenously along with the standard intrathecal analgesic medication reported significantly milder itching than patients who received 2 or 4 mg ondansetron or a saline placebo, Dr. Segal reported at the annual meeting of the Society for Obstetric Anesthesia and Perinatology.

In a randomized double-blinded trial, Dr. Segal and his colleagues at Brigham and Women's Hospital in Boston assigned 40 women planning neuraxial analgesia for labor into four groups. Each patient received spinal analgesia consisting of 25 mg fentanyl plus 2.5 mg bupivacaine. At the same time, they were given intravenous injections of 2, 4, or 8 mg ondansetron or the placebo.

Pruritus and pain were assessed using a 100-mm visual analog scale at the time of the spinal injection and 5,15, 30, 60, and 90 minutes thereafter, Dr. Segal said. Patients were allowed to have 5 mg IV nalbuphine as a rescue medication at any time.

The pattern of pruritus was roughiy similar in all four groups, becoming noticeable within 5 minutes and reaching a peak at 30 minutes in the placebo and highest-dose groups, at about 55 mm and about 25 mm on the visual analog scale, respectively. Peak values in the groups receiving 2 and 4 mg ondansetron were recorded at the 60-minute reading, at approximately 40 mm and 43 mm, respectively.

Analgesia was the same in all four groups. None of the patients required the rescue medication.

Pruritus occurs in 60%-80% of women who receive spinal anesthesia, Dr. Segal said.

These findings suggest that 5-HT3 antagonists such as ondansetron may help relieve that itching, but they're not used routinely because they are very expensive--about $26 for an 8-mg dose at Brigham and Women's.

The fact that not even the patients in he placebo group required the rescue nedication suggests that pruritus is a time-limited problem that may best be treated with reassurance. Dr. Segal added that he now tells his patients that the itching begins to subside within about 30 minutes.

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