Can a motion sickness pill stop semaglutide vomiting? What Vanda's Phase 3 trial found

A Phase 3 trial of tradipitant, a pill already approved in the United States to prevent vomiting from motion sickness, reduced vomiting after a dose of semaglutide, the drug in Ozempic and Wegovy. Vomiting struck 43.0% of people given tradipitant and 58.5% of those given placebo, an absolute difference of 15.5 percentage points, according to results Vanda Pharmaceuticals released on October 27, 2026 [1]. The test used a deliberately harsh single 1 mg semaglutide dose with no gradual escalation, the full data have not been published, and tradipitant is not approved for GLP-1 side effects.

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Why vomiting matters for GLP-1 drugs

Nausea and vomiting are the most familiar costs of semaglutide. In the three placebo-controlled trials behind Wegovy's 2021 approval, which treated 2,116 people for up to 68 weeks, 44% of people on the drug reported nausea and about a quarter reported vomiting, compared with 16% and 6% on placebo. These reactions rose during dose escalation, and 4.3% of people on Wegovy stopped treatment permanently because of a gastrointestinal side effect, against 0.7% on placebo [5].

That is why the label starts semaglutide at 0.25 mg a week and raises it in four-week steps: slow escalation is the standard way to limit gastrointestinal effects [5]. Vanda argues that vomiting and nausea are among the main reasons people stop or never reach a full dose, and cites real-world studies in which roughly half of patients discontinue within a year [1]. That figure is the company's reading of outside studies, not a result of its own trial.

What Study 3601 tested

Study 3601, registered as NCT07446439, is a randomized, quadruple-blind trial comparing tradipitant capsules with placebo capsules taken twice a day for about two weeks [2]. The registry lists adults aged 18 to 65 with a body mass index from 25 to under 40 and no diabetes or other serious chronic disease. People with conditions that independently cause gastrointestinal symptoms were excluded [2].

The challenge was intentionally severe. Every participant received a single 1 mg dose of semaglutide without the weeks of escalation used in practice, a dose Wegovy's label schedules only from week 9, after eight weeks of escalation [1][5]. Vanda describes this as a rigorous test of prevention under a strong vomiting stimulus [1].

The registered primary outcome is the share of participants with at least one vomiting episode over one week, recorded in a daily symptom diary. The key secondary outcome adds severity: at least one vomiting episode together with a worst nausea score of 3 or more [2]. In Vanda's earlier Phase 2 study, that score sat on a 0 to 5 scale where 3 meant moderate or worse [3].

The results, in absolute numbers

Participants in the results: 142 on tradipitant and 164 on placebo, 306 in all [1].
Any vomiting, the primary endpoint: 43.0% (61 of 142) on tradipitant vs 58.5% (96 of 164) on placebo, p=0.006. That is 15.5 points lower in absolute terms, which Vanda reports as a 27% relative reduction [1].
Vomiting with worst nausea of 3 or more, the key secondary endpoint: 33.1% (47 of 142) vs 50.6% (83 of 164), p=0.002, or 17.5 points lower [1].
More than 2 vomiting episodes on more than one day: 6.3% (9 of 142) vs 15.9% (26 of 164) [1].
More than 10 vomiting episodes in total: 2.8% (4 of 142) vs 14.6% (24 of 164) [1].

Where the biggest effects sat

The last two measures carry the largest relative reductions, 60% and 81%. Vanda states they are post hoc and exploratory, meaning they were chosen after the data were in hand, so they describe a pattern rather than confirm one. The p values for the primary and key secondary results were adjusted for trial site [1].

Timing matters too. Almost every vomiting episode in both groups happened by day 2, peaking on day 1, and the gap between drug and placebo was widest on days 1 and 2 [1]. That fits a drug used around the first doses rather than for months.

How a motion sickness drug could block semaglutide vomiting

Tradipitant blocks the neurokinin-1 (NK-1) receptor, which responds to a signalling peptide called substance P. Vanda says it acts on the brainstem vomiting centre, including the area postrema and the nucleus tractus solitarius [1]. FDA approved it as Nereus on December 30, 2025, for preventing vomiting induced by motion in adults [6][7].

The same brainstem region is where semaglutide's unpleasant effects appear to start. In a 2024 Nature study in mice, a team at the Monell Chemical Senses Center found that GLP-1 receptor neurons in the area postrema drove strong aversion along with reduced eating, while neighbouring neurons in the nucleus tractus solitarius produced fullness without aversion. GLP-1 drugs still reduced food intake in mice when the aversion pathway was blocked [8].

That is the hopeful version of the idea: in principle, the sickness and the appetite effect run on separate wiring. It is a mouse finding about circuits, not evidence about tradipitant, and Study 3601 used one semaglutide dose over about a week, so it says nothing about whether blocking vomiting changes weight loss over months [1][8].

What the trial does not show yet

The numbers above come from Vanda's own announcement. No peer-reviewed paper or registry results have been posted, and the registry entry, last updated in April 2026, still lists the trial as recruiting with an estimated 280 participants, fewer than the 306 participants (142 plus 164) in the release's results [1][2]. Vanda has not published a full safety table for the study, saying only that tradipitant was generally well tolerated with no new safety signals [1].

The approved label gives a fuller picture of side effects. In single-dose motion sickness trials, somnolence was reported by 6% of people on the 85 mg dose versus 4% on placebo, and by 12% on 170 mg versus 6%, and fatigue rose in the same way. The label warns that tradipitant can impair driving, and that strong CYP3A4 inhibitors, drugs that slow its breakdown in the liver, can increase exposure [6]. Those findings come from single doses for motion, not from two weeks alongside semaglutide.

The effect also shrank between studies. In Vanda's Phase 2 study, registered as NCT06804603 [4], 116 people received the same single unescalated 1 mg semaglutide dose, and vomiting fell from 58.6% on placebo to 29.3% on tradipitant [3]. In the larger Phase 3, the placebo rate was almost identical but the tradipitant rate was 43.0% [1]. Vanda has not explained the difference in its release.

Most of all, the trial tested the worst case. Real patients climb from 0.25 mg over months, on a schedule the label uses to reduce gastrointestinal reactions [5]. Vanda says a pooled exposure analysis of its two trials showed the benefit held steady across the semaglutide concentrations it observed, and it uses that to argue the effect should carry over to normal dosing [1]. Whether it does is the question a treatment-length trial in people escalating normally would answer.

What happens next

Vanda says it will discuss the results with the FDA and plans to submit a supplemental new drug application to add prevention of GLP-1-associated vomiting to Nereus's label [1]. Unless the FDA approves that, tradipitant's only approved use is preventing motion-induced vomiting [6].

The FDA's review, and any published paper with the full safety data, will show whether a 15-point drop in vomiting under a harsh single-dose test holds up as a reason to add a second drug at the start of GLP-1 treatment. For now the better-established tool remains the one in the label: slow escalation [5].

Frequently asked questions

Is tradipitant approved for Ozempic or Wegovy nausea?

No. The FDA approved tradipitant, sold as Nereus, on December 30, 2025, only for preventing vomiting induced by motion in adults. Vanda plans to ask the FDA to add prevention of GLP-1-associated vomiting after its Phase 3 results.

[6] [7] [1]

How much did tradipitant reduce vomiting in the Phase 3 trial?

After a single 1 mg semaglutide dose, 43.0% of participants on tradipitant vomited, against 58.5% on placebo. That is a 15.5 percentage point absolute difference, which Vanda describes as a 27% relative reduction. The figures come from a company release, not a peer-reviewed paper.

[1]

Why did the trial use a 1 mg semaglutide dose straight away?

Vanda designed the test to provoke a high rate of vomiting so that prevention could be measured clearly. In normal use, Wegovy starts at 0.25 mg and is raised every four weeks, partly to limit gastrointestinal side effects.

[1] [5]

What are tradipitant's side effects?

In single-dose motion sickness trials summarised in its FDA label, the most common side effects were somnolence, headache and fatigue. The label warns it may impair driving and that strong CYP3A4 inhibitors can raise its levels. Vanda has not published a full safety table for the semaglutide study.

[6] [1]

Does blocking nausea reduce semaglutide's effect on appetite?

No human trial has answered that. A 2024 mouse study found that separate brainstem neurons drive aversion and fullness, and that GLP-1 drugs still reduced food intake when the aversion pathway was blocked. Study 3601 used one dose over about a week and did not measure weight loss.

[8] [1]