Gabapentin for pain control after osmotic dilator insertion and prior to dilation and evacuation procedure: A randomized controlled trial
Awarded 2017
Complex Family Planning Fellowship Research
Natasha Schimmoeller, MD, MPH, MA
University of California, Davis

Background: Overnight osmotic dilators are an essential, yet potentially painful, component of cervical preparation prior to dilation and evacuation procedure. Little research has been done evaluating women’s experience with osmotic dilators. Gabapentin is an attractive option for dilator-associated pain due to low cost, no addictive potential, and few medical contraindications.
Statement of purpose: We propose a study to evaluate the effect of gabapentin on the pain experienced with osmotic dilators prior to dilation and evacuation procedure.
Methodology: We conducted a randomized, double-blind, placebo-controlled trial of women presenting for cervical preparation with osmotic dilators at 15w0d – 23w5d gestation, prior to dilation and evacuation procedure scheduled the subsequent day. Women were randomized to gabapentin 600 mg or placebo. Participants took their first dose of their assigned study drug 30 minutes prior to dilator placement, with re-dosing at 8 hours after dilator placement. Women left the clinic with standard options of ibuprofen and acetaminophen with codeine to take as needed overnight for pain.
The primary outcome was the median change in pain score (on a numeric rating scale (NRS) of 0-10) from baseline to 8 hours after dilator placement among women randomized to gabapentin vs. placebo. Secondary outcomes included median change in pain score from baseline to 5 minutes, 2 hours, 4 hours, and 18-24 hours after dilator placement (when women came for dilation and evacuation procedure the next day). We also evaluated analgesic use, gabapentin-related side effects, and aimed to characterize women’s pain experience with osmotic dilators in general. Women were sent text messages while at home to obtain study data.
To detect a 2-point difference on the NRS and account for up to 20% non-response to text messages, a sample size of 60 women was needed. Given the high clinical volume at our site, this sample size was doubled to a total of 120 women to better evaluate secondary outcomes. Randomization was stratified by presence or absence of vaginal parity given possible impact of a parous cervix on dilator-associated pain.
Important findings: From March 2017-May 2018, 121 women were randomized, with 119 women ultimately followed over the course of the study. Demographic details were similar between groups. The median change in pain score was not statistically different among women who received gabapentin compared to placebo at any time point, regardless of prior vaginal parity. Median pain scores were low overall and there was no statistically significant difference between vaginally nulliparous or parous women. However, 64% of women used acetaminophen with codeine and 75% used ibuprofen, suggesting continued demand for analgesics. Women who received gabapentin reported more tiredness and dizziness, consistent with known medication side-effect. Response to text messaging was high, with 84% of women responding to all messages.
Conclusion: Gabapentin does not decrease pain with overnight osmotic dilators and causes expected drug-related side effects. Though most women report low pain scores overnight, some still use narcotic pain medication. Text messaging has high response rates in abortion research.