We found eight drugs that reliably prevented nausea or vomiting after surgery. The drugs prevented nausea or vomiting in three or four people out of every 10 who would have vomited or felt nauseated with a placebo. We did not find reliable evidence that one drug was better than another. A person's age or sex, the type of surgery, or the time the drug was given did not change the effect of a drug. When drugs were given together, their effects simply added. Side effects were mild and affected four out of 100 people for the two drugs most studied.
Either nausea or vomiting are reported to affect, at most, 80 out of 100 people after surgery. If all 100 of these people are given a drug, about 28 would benefit and 72 would not. Nausea or vomiting are usually less common and therefore drugs are usually less useful.
Doctors should research how often drugs cause severe side effects.