NEW ORLEANS – Adding gabapentin to standard therapy did not significantly reduce vaso-occlusive pain in most patients with sickle cell disease enrolled in a phase 2 trial.
In the entire cohort, there were no significant differences in pain response between patients who received gabapentin and those who received placebo. However, patients with the HbSS genotype had a significantly greater decrease in pain score from baseline to discharge if they received gabapentin rather than placebo.
Additional studies are needed to confirm these findings because this trial was limited by a small sample size, according to study investigator, of St. Jude Children’s Research Hospital in Memphis. Dr. Puri presented the trial at the annual meeting of the American Society of Pediatric Hematology/Oncology.
Theincluded 86 evaluable patients who had vaso-occlusive pain and a pain score of at least 4. All patients received standard therapy for vaso-occlusive pain and were randomized to receive placebo (n = 44) or a single oral dose of gabapentin at 15 mg/kg (n = 42).
Baseline characteristics were similar between the treatment arms. For the entire cohort, the mean age was 11.8 years (range, 1-21 years), and 51% of patients were male. Forty-four patients had the HbSS genotype, 25 had the HbSC genotype, 8 had HbS/beta0-thalassemia, and 9 had other genotypes.
The mean pain score at baseline was 7.8 for the entire cohort, 8.0 for the gabapentin arm, and 7.7 for the placebo arm.
For the entire cohort, there was no significant difference in pain response between the gabapentin and placebo arms.
The proportion of patients who experienced a greater than 33% decrease in pain from baseline to 3 hours posttreatment was 67% in the gabapentin arm and 59% in the placebo arm (P = .23). The proportion of patients who experienced a greater than 33% decrease from baseline to discharge from the acute care clinic was 75% and 61%, respectively (P = .18).
In the entire cohort, decreases in pain scores from baseline to 3 hours posttreatment were not significantly different between the gabapentin and placebo arms, at 1.3 and 0.7, respectively (P = .74). Likewise, decreases in pain scores from baseline to discharge were not significantly different, at 1.6 and 0.8 (P = .38).
Among patients who had the HbSS genotype, there was a significantly greater decrease in pain score from baseline to discharge in the gabapentin arm than in the placebo arm, 5.9 versus 3.6 (P = .03). However, there were no other significant differences in pain response for the HbSS subgroup.
There were no significant differences in opioid consumption or hospitalization for the HbSS subgroup or the entire cohort. For the entire cohort, the mean morphine equivalent dose from baseline to 3 hours posttreatment was 0.16 mg/kg in the gabapentin arm and 0.17 mg/kg in the placebo arm (P = .89). For the HbSS subgroup, the mean dose was 0.16 mg/kg and 0.15 mg/kg, respectively (P = .93).
In the entire cohort, 24% of patients in the gabapentin arm and 27% of those in the placebo arm were hospitalized (P = .71). In the HbSS subgroup, hospitalizations occurred in 11% and 35% (P = .15).
Dr. Puri pointed out several challenges that led to limitations in this study. Specifically, the investigators had to obtain patient consent while delivering standard treatment, while patients were in pain and distress, and from patients who had already received opioids and were sleepy. Additionally, gabapentin had to be delivered within 1 hour of opioid administration, and a lack of after-hours staff limited enrollment.
“These challenges led to one of our biggest limitations, which was a small sample size, leading to a limited power to observe real differences,” Dr. Puri said. “We also defined a very short time period of evaluation for the primary outcomes; that was 3 hours from the gabapentin dose or placebo dose. This limited our capability to see real differences if they existed.”
Dr. Puri said additional studies with larger sample sizes are needed to confirm these findings. She added that efforts to better characterize pain in sickle cell disease could reveal patients who may benefit from gabapentin because they have a neuropathic component to their pain.
The trial was sponsored by St. Jude Children’s Research Hospital in collaboration with Scan|Design Foundation. Dr. Puri did not provide disclosure information at the meeting.