Icon Legend

This session is not in your schedule.

This session is in your schedule. Click again to remove it.

Presentation Icons

Additional registration fee required

Faculty have requested this content not be shared outside of the session

CME Credit Offered

Abstract Award

Recording available 2/16-5/2

AIUM Credit

Foundation Awardee

Poster Icons

Abstract Award

Foundation Awardee

Poster Session 3

Category: Clinical Obstetrics

Poster Session 3

(721) Off-label Use of Mirtazapine and Olanzapine for Hyperemesis Gravidarum: A Retrospective Cohort Study

Thursday, February 12, 2026

10:30 AM - 12:00 PM

Submitting Author and Presenting Author(s)

Andrew Housholder, MD (he/him/his)

The Morning Sickness Clinic, LLC
Birmingham, Alabama, United States

Coauthor(s)

MF

Marlena Fejzo, PhD

University of Southern California, Keck School of Medicine
Los Angeles, California, United States
EL

Ellie Lewis, N/A

John Hopkins University
Baltimore, Maryland, United States
IC

Isabella Clements, N/A

University of Alabama at Birmingham
Birmingham, Alabama, United States

Objective:
To evaluate the effectiveness of off-label mirtazapine and olanzapine for managing hyperemesis gravidarum (HG) unresponsive to standard therapies. Mirtazapine’s 5-HT3 and H1 antagonism reduces nausea, while alpha-2 blockade increases appetite. Olanzapine’s D2, 5-HT3, H1, and M1 activity reduces nausea and vomiting, with evidence supporting its use in postoperative, chemotherapy-related, and cyclic vomiting.

Study Design:
A retrospective chart review was conducted at The Morning Sickness Clinic, which treated ~1300 HG patients over 3 years. 100 patients who failed standard antiemetics were prescribed either mirtazapine (7.5–15 mg) or olanzapine (5 mg) based on physician clinical judgment, in addition to other meds and IV fluids. Outcomes were assessed using HELP and PUQE scores, vomiting frequency, and weight change at follow-up 1–3 weeks post-initiation. The study was deemed IRB exempt (BRANY IRB #24-12-337-1652)

Results:
Among 62 patients prescribed mirtazapine, 46 had follow-up visits (mean interval: 11 days; prior meds: 3.3; mean weight loss: 7.8 lbs; mean EGA: 12.8 weeks). At followup, HELP scores decreased by 10.0 points (SD ±10.9; p < 0.001), PUQE scores decreased by 2.4 (SD ±4.2; p < 0.001), vomiting decreased from 4.7x to 2.2x/day (Δ 2.5; SD ±4.1; p < 0.001), and 83% of patients gained weight (mean: 2.9 lbs; SD ±4.5; p < 0.001)
Among 38 patients prescribed olanzapine, 29 had follow-up (mean interval: 10 days; prior meds: 3.9; mean weight loss: 7.9 lbs; mean EGA: 15.2 weeks). At followup, HELP scores decreased by 14.6 (SD ±11.6; p < 0.001), PUQE scores decreased by 3.4 (SD ±3.5; p < 0.001), vomiting decreased from 6.8x to 2.7x/day (Δ 4.1; SD ±4.9; p < 0.001), and 90% of patients gained weight (mean: 6.2 lbs; SD ±5.9; p < 0.001)

Subgroup analysis of patients treated before 12 weeks (mirtazapine 25; olanzapine 10; mean EGA 10.8) showed similar benefit.

Conclusion:
In patients with refractory HG, mirtazapine and olanzapine were associated with reduced nausea and vomiting and improved weight stabilization. These findings support further study of these agents as adjunctive therapies for severe HG.