Vitamin B6 as a potential antiemetic
Limited evidence suggests pyridoxine can reduce the incidence of postoperative nausea and vomiting
As early as 1995, a double-blind, randomized controlled trial (RCT) demonstrated the effectiveness of using pyridoxine (vitamin B6) for the treatment of nausea during pregnancy. Women who took 10 mg of pyridoxine every 8 hours had significantly lower nausea scores compared to controls. There was no significant difference in episodes of vomiting. In 2023, a meta-analysis reaffirmed the benefits of using pyridoxine to reduce nausea during pregnancy.
If pyridoxine can reduce nausea during pregnancy, could it also help reduce postoperative nausea and vomiting (PONV)? To my knowledge, only one double-blind RCT exists to begin answering this question. Researchers looked at patients undergoing laparoscopic gynecologic surgery and randomized them to receive pyridoxine 200 mg prior to induction of anesthesia (n = 120) or to a control group (n = 120). Both groups received 10 mg of dexamethasone and 8 mg of ondansetron during their anesthetics.
Participants in the pyridoxine group experienced significantly lower rates of nausea compared to controls (12.5% vs. 35.0%; relative risk [RR] 0.36; 95% confidence interval [CI] 0.21 to 0.61; p < 0.001). There was no difference in the incidence of postoperative vomiting.
While these results seem promising, the study had several limitations. Most significantly, it is unclear how these effects would translate to patients undergoing non-gynecologic surgeries. Second, patients in the control group experienced significantly more hypotension compared to those in the pyridoxine group (52.5% vs. 30.8%). As hypotension is associated with an increased incidence of PONV, this difference alone could potentially have biased the results toward showing a benefit.1
Even with this limited evidence, I wanted to write about this study because pyridoxine is cheap and very well tolerated in a single dose.2 It is certainly safer than some other widely used medications, such as scopolamine, which is associated with increased postoperative mortality.3
The fifth consensus guidelines for the treatment of PONV were released in 2025 and made no mention of pyridoxine. Hopefully by the time the sixth revision is published, we will have more robust RCT data evaluating this affordable, low-risk B vitamin. Perhaps, one of you readers will want to do some of that research?
An oddity of this trial is the average of zero morphine milligram equivalents consumed in both groups.
Chronic, high doses can cause neuropathy.
While the fifth PONV consensus guidelines mention its risk of urinary retention, they fail to mention the association with increased mortality. We don’t know if causality exists, but given the plethora of other available drugs, I fail to see any compelling reason to use scopolamine.