Gabapentin's anti-nausea and anti-emetic effects: a review

Preoperative Gabapentin for Pain Control: A Randomized, Placebo-controlled Clinical Trial in Patients Undergoing Inguinal Hernioplasty

PURPOSE

The perioperative use of gabapentin has been suggested to reduce postoperative pain and opioid consumption. However, there is a variation in clinical practice, the type of surgery and the administration time seem to be distinct between the available studies. We assess whether gabapentin administered before surgery reduces postoperative pain in patients who have undergone inguinal hernioplasty.

DESIGN

This is a double-blind, randomized, and placebo-controlled trial.

METHODS

Seventy-seven patients scheduled for inguinal hernioplasty were randomized in two groups to receive gabapentin (900 mg) or placebo in the perioperative period. The primary outcome was analgesia measured by visual analog scale up to 30 days after surgery. The secondary outcomes such as morphine consumption, nausea, headache, and sedation have been also described.

FINDINGS

Patients who received gabapentin had lower postoperative pain scores compared to the control group, P < .001. The postoperative morphine use was significantly lower in the gabapentin (5.3%) versus placebo group (74.4%), P < .001. No significant difference between groups was observed for the occurrence of adverse events.

CONCLUSIONS

The perioperative administration of gabapentin was effective in reducing postoperative pain and had an important effect in decreasing morphine use. Together, our data reveal a long-lasting opioid-sparing effect of gabapentin in patients who underwent inguinal hernioplasty.

Inpatient Management of Hyperemesis Gravidarum

Hyperemesis gravidarum has a reported incidence of approximately 0.3-3% of pregnancies. Without treatment, refractory hyperemesis gravidarum can result in dehydration, electrolyte deficiencies, and severe nutritional deficiencies, resulting in significant maternal morbidity. The overall goals of inpatient management of refractory hyperemesis gravidarum are the resumption of oral intake to an adequate level to maintain hydration and nutrition, including the ability to tolerate oral pharmacotherapy. Patients initially are stabilized with rehydration and electrolyte repletion. There are numerous pharmacotherapeutics available that can be administered intravenously to control symptoms when oral intake is not an option. However, despite maximizing typical antiemetics, there will be cases refractory to these medications, and alternative pharmacotherapeutics and nutrition-support modalities must be considered. Mirtazapine, olanzapine, corticosteroids, and gabapentin are examples of alternative pharmacotherapeutics, and enteral and parenteral nutrition are alternative therapies that can be used when oral intake is not tolerated for prolonged time periods with ongoing weight loss. In refractory cases of hyperemesis gravidarum, the risks and benefits of these alternative forms of management must be considered, along with the risks of undertreated hyperemesis gravidarum and the overall effect of hyperemesis gravidarum on patients' quality of life.

GIP receptor agonism blocks chemotherapy-induced nausea and vomiting

OBJECTIVE

Nausea and vomiting remain life-threatening obstacles to successful treatment of chronic diseases, despite a cadre of available antiemetic medications. Our inability to effectively control chemotherapy-induced nausea and vomiting (CINV) highlights the need to anatomically, molecularly, and functionally characterize novel neural substrates that block CINV.

METHODS

Behavioral pharmacology assays of nausea and emesis in 3 different mammalian species were combined with histological and unbiased transcriptomic analyses to investigate the beneficial effects of glucose-dependent insulinotropic polypeptide receptor (GIPR) agonism on CINV.

RESULTS

Single-nuclei transcriptomics and histological approaches in rats revealed a topographical, molecularly distinct, GABA-ergic neuronal population in the dorsal vagal complex (DVC) that is modulated by chemotherapy but rescued by GIPR agonism. Activation of DVCGIPR neurons substantially decreased behaviors indicative of malaise in cisplatin-treated rats. Strikingly, GIPR agonism blocks cisplatin-induced emesis in both ferrets and shrews.

CONCLUSION

Our multispecies study defines a peptidergic system that represents a novel therapeutic target for the management of CINV, and potentially other drivers of nausea/emesis.

Impact of timing of preoperative gabapentin administration on postoperative somnolence

Context

Enhanced Recovery After Surgery (ERAS) is a multimodal protocol aimed to improve quality of postoperative recovery, minimize complications, and optimize overall self-regulation. Preoperative gabapentin decreases postoperative pain but can be associated with prolonged postoperative somnolence and respiratory depression risk. Although it is known that gabapentin affects the postoperative course, it is unclear if the timing of preoperative administration affects this finding.

Objectives

This study aims to assess the optimal preoperative timing for gabapentin administration in patients undergoing gynecologic surgery to minimize postoperative somnolence risk.

Methods

A retrospective cohort study evaluated patients who underwent major gynecologic surgery and received preoperative gabapentin. Patients were grouped based on timing from gabapentin administration to surgical incision (<4 h group vs. ≥4 h group). Preoperative, intraoperative, and postoperative data were abstracted and compared. Univariate associations between the timing of gabapentin administration and the patient and surgical characteristics and outcomes were tested utilizing two-sample equal-variance t-tests, linear model ANOVA, or Fisher’s exact tests. Associations between the timing of gabapentin administration and the time until the Richmond Agitation Sedation Scale (RASS) score of 0 were modeled utilizing linear regression, adjusted for age, initial postoperative anesthesia care unit (PACU), RASS score, and postoperative narcotics.

Results

Each group contained 127 patients. Demographics were similar except for age (<4 h group mean=44.2 years; ≥4 h group mean=40.5 years; p=0.021), chronic pain (<4 h group=17.6%; ≥4 h group=43.3%; p<0.001), and surgical indication (<4 h group=pelvic pain [29.1%]; ≥4 h group=pelvic pain [51.2%]; p=0.007). The <4 h group had a similar postoperative narcotic administration (<4 h group mean morphine milligram equivalents [MME]=3.667; ≥4 h group mean MME=4.833; p=0.185). The minutes from surgical closure until the patient received a RASS score of 0 and initial PACU pain score (Visual Analogue Scale [VAS]) were similar. The initial PACU oxygen administration volume, hours from surgical closure until the patient transitioned to room air, and initial PACU respiratory rate were similar. The PACU duration, admission secondary to somnolence, and initial PACU Glasgow Coma Scale (GCS) score showed no difference. Postoperative nausea/vomiting was decreased in the ≥4 h group (<4 h group=24.4%; ≥4 h group=13.4%; p-value=0.036), and urinary retention (<4 h group=14.2%; ≥4 h group=5.5%; p-value=0.033) was decreased in the ≥4 h group.

Conclusions

The timing of gabapentin administration less than or more than 4 h preoperatively in patients ≥18 years does not significantly affect postoperative somnolence or respiratory depression. Further, it does not have a significant effect on GCS scores or VAS scores.

Gabapentin and intrathecal morphine combination therapy results in decreased oral narcotic use and more consistent pain scores after posterior spinal fusion for adolescent idiopathic scoliosis

Background

Gabapentin and intravenous patient-controlled analgesia (PCA) can reduce postoperative pain scores, postoperative opioid use, and time to completing physical therapy compared to PCA alone after posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). Gabapentin combined with intrathecal morphine has not been studied. The primary purpose of this retrospective study was to evaluate whether perioperative gabapentin and intrathecal morphine provide more effective pain control than intrathecal morphine alone after PSF for AIS.

Methods

Patients aged 11 to 18 years who underwent PSF for AIS were identified. Patients who received intrathecal morphine only (ITM group) were matched by age and sex to patients who received intrathecal morphine and perioperative gabapentin (ITM+GABA group). The ITM+GABA group received gabapentin preoperatively and for up to 2 days postoperatively. Both groups received oxycodone and the same non-narcotic adjuvant medications.

Results

Our final study group consisted of 50 patients (25 ITM, 25 ITM+GABA). The ITM+GABA group had significantly lower mean total oxycodone consumption during the hospitalization (0.798 vs 1.036 mg/kg, P<0.015). While the ITM group had a lower mean pain score between midnight and 8 am on POD 1 (2.4 vs 3.7, P=0.026), pain scores were significantly more consistent throughout the postoperative period in ITM+GABA group. The ITM+GABA group experienced less nausea/vomiting (52% vs 84%, P=0.032) and pruritus (44% vs 72%, P=0.045). Time to physical therapy discharge and length of hospital stay were similar.

Conclusion

Addition of gabapentin resulted in reduced oral opioid consumption and more consistent postoperative pain scores after PSF for AIS. The patients who received intrathecal morphine and gabapentin also experienced a lower rate of nausea/vomiting and pruritus.

Trial registration

All data was collected retrospectively from chart review, with institutional IRB approval. Trial registration is not applicable.

Toxicity assessment of concurrent gabapentin/pregabalin administration with high-dose melphalan in autologous hematopoietic cell transplant recipients

A theoretical pharmacokinetic interaction mediated through L-amino acid transporter 1 and 2 exists between gabapentin (GP) and pregabalin (PG) with melphalan. Peripheral neuropathy is a common toxicity of various multiple myeloma regimens commonly utilized prior to autologous hematopoietic cell transplant (auto-HCT) with high-dose melphalan (HD-Mel). Therefore, it is likely concurrent administration of either GP or PG will occur in patients receiving HD-Mel conditioning for auto-HCT, which could potentially increase cellular uptake and worsen the mucosal injury. A retrospective chart review of adult patients from January 2012 to July 2016 who received HD-Mel (140-200 mg/m²) at West Virginia University Medicine was performed to assess toxicity and outcomes in these patients. A total of 80 patients were included in the study, with 30 patients receiving GP or PG and 50 control patients. There were no significant differences in grade 2 or higher mucositis, admissions for nausea/vomiting/diarrhea, intravenous opioid requirements, oral topical therapies, antidiarrheal medication use, rescue anti-emetics, days of nausea or vomiting, pain scores, neutrophil or platelet engraftment, treatment-related mortality, progression-free survival, or overall survival. Our data suggest that it is safe to continue GP/PG therapy throughout HD-Mel therapy, with no negative transplant outcomes. Prospective studies or evaluations of larger databases are necessary to better characterize the clinical effect of concomitant therapy.

The Management of Nausea and Vomiting Not Related to Anticancer Therapy in Patients with Cancer

OPINION STATEMENT

In cancer patients, the management of nausea and vomiting that is not directly related to treatment is challenging. Much current practice is based on expert opinion and anecdote. Fortunately, over recent years, a number of quality trials have been undertaken to strengthen the evidence base that guides the care of our patients with these distressing symptoms. Much is still unknown however. In this article, we present the latest literature that addresses some of the outstanding issues.

Effect of gabapentin on hyperemesis gravidarum: a double-blind, randomized controlled trial

BACKGROUND

Hyperemesis gravidarum is a disabling disease of nausea, vomiting, and undernutrition in early pregnancy for which there are no effective outpatient therapies. Poor weight gain in hyperemesis gravidarum is associated with several adverse fetal outcomes including preterm delivery, low birthweight, small for gestational age, low 5-minute Apgar scores, and neurodevelopmental delay. Gabapentin is most commonly used clinically for treating neuropathic pain but also substantially reduces chemotherapy-induced and postoperative nausea and vomiting. Pregnancy registry data have shown maternal first-trimester gabapentin monotherapy to be associated with a 1.2% rate of major congenital malformations among 659 infants, which compares favorably with the 1.6% to 2.2% major congenital malformation rate in the general population. Open-label gabapentin treatment in hyperemesis gravidarum was associated with reduced nausea and vomiting and improved oral nutrition.

OBJECTIVE

This study aimed to determine whether gabapentin is more effective than standard-of-care therapy for treating hyperemesis gravidarum.

STUDY DESIGN

A double-blind, randomized, multicenter trial was conducted among patients with medically refractory hyperemesis gravidarum requiring intravenous hydration. Patients were randomized (1:1) to either oral gabapentin (1800-2400 mg/d) or an active comparator of either oral ondansetron (24-32 mg/d) or oral metoclopramide (45-60 mg/d) for 7 days. Differences in Motherisk-pregnancy-unique quantification of nausea and emesis total scores between treatment groups averaged over days 5 to 7, using intention-to-treat principle employing a linear mixed-effects model adjusted for baseline Motherisk-pregnancy-unique quantification of nausea and emesis scores, which served as the primary endpoint. Secondary outcomes included Motherisk-pregnancy-unique quantification of nausea and emesis nausea and vomit and retch subscores, oral nutrition, global satisfaction of treatment, relief, desire to continue therapy, Nausea and Vomiting of Pregnancy Quality of Life, and Hyperemesis Gravidarum Pregnancy Termination Consideration. Adjustments for multiple comparisons were made employing the false discovery rate.

RESULTS

A total of 31 patients with hyperemesis gravidarum were enrolled from October 2014 to May 2019. Among the 21 patients providing primary outcome data (12 assigned to gabapentin and 9 to the active comparator arm), 18 were enrolled as outpatients and all 21 were outpatients from days 5 to 7. The study groups' baseline characteristics were well matched. Gabapentin treatment provided a 52% greater reduction in days 5 to 7 baseline adjusted Motherisk-pregnancy-unique quantification of nausea and emesis total scores than treatment with active comparator (95% confidence interval, 16-88; P=.01). Most secondary outcomes also favored gabapentin over active comparator treatment including 46% and 49% decreases in baseline adjusted Motherisk-pregnancy-unique quantification of nausea and emesis nausea (95% confidence interval, 19-72; P=.005) and vomit and retch subscores (95% confidence interval, 21-77; P=.005), respectively; a 96% increase in baseline adjusted oral nutrition scores (95% confidence interval, 27-165; P=.01); and a 254% difference in global satisfaction of treatment (95% confidence interval, 48-459; P=.03). Relief (P=.06) and desire to continue therapy (P=.06) both showed trends favoring gabapentin treatment but Nausea and Vomiting of Pregnancy Quality of Life (P=.68) and Hyperemesis Gravidarum Pregnancy Termination Consideration (P=.58) did not. Adverse events were roughly equivalent between the groups. There were no serious adverse events.

CONCLUSION

In this small trial, gabapentin was more effective than standard-of-care therapy for reducing nausea and vomiting and increasing oral nutrition and global satisfaction in outpatients with hyperemesis gravidarum. These data build on previous findings in other patient populations supporting gabapentin as a novel antinausea and antiemetic therapy and support further research on gabapentin for this challenging complication of pregnancy.

A Comparative Study Between Ondansetron and Gabapentin for Prevention of Postoperative Nausea and Vomiting Following Maxillofacial Surgery

Background and Aim

Gabapentin is an antiepileptic drug with antiemetic properties. We evaluated prophylactic oral gabapentin as compared with ondansetron for postoperative nausea and vomiting (PONV) in patients undergoing maxillo facial surgery.

Settings and Design

A double-blind, randomized study in a teaching hospital.

Materials and Methods

Seventy patients of ASA physical status I and II, scheduled to undergo maxillofacial surgery, were randomly assigned into two groups to receive 300 mg gabapentin or 8 mg ondansetron 1 h before surgery. Standard anaesthesia technique was used in all patients. Students' t test for difference of means between two groups was used for continuous variables. Chi square or Fisher's exact test was used for comparing proportion between two groups. Kaplan-Meier survival analysis was performed to compare the time to event observed between ondansetron and gabapentin groups. Log-rank test was performed to detect statistical significance of time to events between two groups.

Results

There was no significant difference in incidence of PONV between two groups within 2 h postoperatively. No incidence of PONV was observed in gabapentin group within 2-24 h as compared to ondansetron group in which PONV was observed in five cases.

Conclusion

Gabapentin effectively suppresses PONV in maxillo facial surgery.

Gabapentinoid prescription in Oral Medicine and Oral Surgery practice. Part II − a systematic scoping review of the literature

Introduction: Gabapentinoids, pregabalin and gabapentin, neuronal voltage-gated calcium channel inhibitors are first-line treatments for painful neuropathic conditions (and several non-neuropathic painful conditions). Nevertheless, their efficacy and prescription in Oral Medicine and Oral Surgery practice has received little attention so far. A previous article, the first of a two-part series, presented the experience of a French tertiary orofacial pain clinic regarding the prescription of gabapentinoids in orofacial conditions. This second article aimed to explore the scientific literature on the subject. Material and methods: A systematic scoping review was conducted on multiple relevant databases (MEDLINE®, Cochrane®, Agence Nationale de Sécurité du Médicament et des produits de santé, Haute Autorité de Santé) and journal archives (JOMOS, JSOMFS) to assess the indications, non-indications and contraindications of gabapentinoids in an Oral Medicine/Oral Surgery context. Results: Out of 131 records selected during the initial screening, 34 matched the inclusion criteria and were used for subsequent analyses. Gabapentinoids were prescribed in three clinical contexts: orofacial pain management (32 studies), anxiolysis (1 study) and prevention of postoperative nausea/vomiting (1 study), with variable quality of evidence: high (6 studies), moderate (3 studies), low (5 studies) and very low (20 studies) quality studies (GRADE scale). Untoward effects of gabapentinoids were reported in 16 studies, mainly neurological (vertigo, drowsiness, sedation) and gastro-intestinal (nausea, vomiting, diarrhea, constipation). Gabapentinoids were ineffective in preemptive and postoperative analgesia and for the management of mucositis-related pain. Discussion: There is some evidence supporting the use of gabapentinoids in Oral Medicine/Oral Surgery in adherence with current practices observed in France and other countries (practices often extrapolated from their use in other non-orofacial painful conditions). The methodological quality of the studies included in this scoping review is often poor and publication bias is most probable in this field. Therefore, any conclusion drawn from such studies must be subject to circumspection. Conclusion: Data obtained from the present scoping review suggests the potential use of gabapentinoids as second-line treatments for anxiolysis, prevention of postoperative nausea/vomiting and the management of trigeminal neuralgia and masticatory myalgia. Other potential indications of gabapentinoids in Oral Medicine/Oral Surgery practice include cranial neuralgias, post-traumatic trigeminal neuropathies, first bite syndrome, burning mouth syndrome and migraine prophylaxis, when other treatment options are inefficient or unavailable.

Trends in Gabapentin Prescribing in a Commercially Insured U.S. Adult Population, 2009-2016

BACKGROUND

Gabapentin is prescribed for a variety of conditions and is often used off label. It is important to understand the prevalence of gabapentin prescribing and the characteristics of individuals who are prescribed gabapentin, given increasing concern regarding its potential for misuse.

OBJECTIVES

To (a) examine state- and region-level prevalence and trends in gabapentin prescribing from 2009 to 2016 and (b) characterize demographic and clinical characteristics of individuals prescribed gabapentin in a nationwide population of commercially insured adults.

METHODS

This retrospective, longitudinal study examined trends in gabapentin prescribing from 2009 to 2016. The study population included individuals aged 18-64 years who were enrolled in a commercial insurance plan at any point from 2009 to 2016. Individuals who were prescribed gabapentin were defined as beneficiaries with at least 1 gabapentin prescription claim in a calendar year (CY). A cross-sectional descriptive analysis was performed to examine differences in demographic and clinical characteristics of individuals prescribed or not prescribed gabapentin in CY 2016.

RESULTS

The prevalence of gabapentin prescribing nearly doubled from 2009 to 2016. During this time, gabapentin prescribing increased in every state (range: 44%-179%). State-specific prevalence rates in 2016 varied from 12.7 to 43.9 per 1,000 beneficiaries. Overall, 2.7% of beneficiaries filled ≥ 1 gabapentin prescription in 2016. Individuals prescribed gabapentin were more likely to fill opioid prescriptions (60.8% vs. 16.5%, P < 0.01); reside in the South (53.7% vs. 47%, P < 0.01); be female (62.5% vs. 52.3%, P < 0.01); and be aged 55-64 years (41.7% vs. 21.2%, P < 0.01) compared with the comparator. Individuals who were prescribed gabapentin also had significantly higher rates of seizure disorders, neuropathic pain, mental health disorders, substance use disorders, and diabetes.

CONCLUSIONS

The prevalence of gabapentin prescribing among a U.S. privately insured population has increased steadily in recent years. Additional research should examine coprescribing of gabapentin in the context of the opioid epidemic.

DISCLOSURES

The project described in this study was supported by the NIH National Center for Advancing Translational Sciences through grant number UL1TR001998. This study was also partially supported by grant number 2017-PM-BX-K026 (Data-Driven Responses to Prescription Drug Misuse in Kentucky) awarded by the Bureau of Justice Assistance. Viewpoints or opinions in this document are those of the authors and do not necessarily represent the official position or policies of the U.S. Department of Justice or the official views of the NIH. The authors do not have any conflicts of interest to report. Portions of this study have been previously presented in poster presentations at the 2019 Academy Health Annual Research Meeting; June 2-4, 2019; Washington, DC, and the 2019 University of Kentucky Substance Use Research Day; March 3, 2019; Lexington, KY.

An investigation into the effect of gabapentin capsules on the reduction of nausea and vomiting after chemotherapy in cancerous patients under platinum-based treatment

Introduction and Objective:

Chemotherapy-induced nausea and vomiting (CINV) is a condition that occur in most patients. This study aimed to investigate the effect of gabapentin capsules on the reduction of chemotherapy-induced nausea and vomiting in patients admitted in the hematological ward for adult patients with platinum-based treatment.

Materials and Methods:

The present study was a randomized clinical trial, which consisted of a control group and an experimental one. The study population consisted of 126 women and men with colonic and gastric cancer who were admitted to Ahwaz Shafa Hospital of adult hematology ward. Of these, 120 subjects were eligible to enter the study. Immediately after chemotherapy, gabapentin capsules were taken. Up to 72 hours later, nausea and vomiting were compared. Descriptive statistics was used to investigate the demographic characteristics. Paired t-test, independent t-test and ANOVA were used to compare the results.

Results:

The results showed that most of the patients had gastric cancer in the experimental (70%) and control group (66.66%). The results also showed that chemotherapy-induced nausea and vomiting in gabapentin recipient group was different from the placebo group. Accordingly, chemotherapy induced nausea and vomiting in gabapentin group was lower than the placebo group.

Conclusion:

Post-operative nausea and vomiting is an unpleasant experience. Today, the patients find it worse than pain, and they believe it is hard to afford the cost of treatment. Gabapentin seems to be a good drug for reducing nausea and vomiting.

Practical Perspectives in the Treatment of Nausea and Vomiting

Nausea and vomiting result from complex interactions between afferent and efferent pathways of the gastrointestinal tract, central nervous system, and autonomic nervous system. Afferent pathways from the vagus nerve, vestibular system, and chemoreceptor trigger zone project to nucleus tractus solitarius, which in turn relays signals to the central pattern generator to initiate multiple downstream pathways resulting in symptoms of nausea and vomiting. There is increasing evidence that the central pathway of chronic nausea is different from that of acute nausea and vomiting-and closely resembles that of neuropathic pain. This improved understanding of chronic nausea has resulted in a paradigm shift with regard to management strategy. Although conventional therapies such as antiemetics and prokinetics are commonly used to manage acute nausea and vomiting, they are historically not as effective in treating chronic nausea. Recently, neuromodulator agents, such as tricyclic antidepressants, gabapentin, olanzapine, mirtazapine, and benzodiazepines, and cannabinoids have been shown to be efficacious in the treatment of nausea and vomiting, and may be useful in the treatment of chronic symptoms. There is a need to study these agents, especially in the management of chronic functional nausea. Improved understanding of the central and peripheral circuitry of nausea and vomiting symptoms will allow for enhanced utilization of the currently available medications, and the development of novel therapeutic options.

Regulating gabapentin as a drug of abuse: A survey study of Kentucky community pharmacists

OBJECTIVES

As the number of gabapentin prescriptions has increased, so have reports of its misuse and diversion. This trend has led some states to closer monitoring of gabapentin dispensing through prescription drug monitoring programs (PDMPs). The objective of this study was to collect and analyze Kentucky community pharmacists' perceptions of gabapentin misuse and diversion, and their support or opposition to regulatory efforts to reclassify the drug as a controlled substance (CS).

METHODS

Responses were collected using an online survey sent by e-mail to all pharmacists practicing in Kentucky in August 2016. The survey collected basic demographic characteristics and pharmacists' experience with gabapentin dispensing. Descriptive statistics were calculated using question response frequencies. Pearson's chi-squared statistics were calculated to examine the distribution of support for gabapentin as a CS in Kentucky across each of the categories of the individual variables. Logistic regression was used to estimate the effects of pharmacist demographic characteristics and experiences with gabapentin on their support of gabapentin reclassification as a CS.

RESULTS

One thousand seven hundred sixty-nine surveys were collected (response rate = 34.2%). Responding community pharmacists (n = 1084) believe that the abuse and diversion of gabapentin are a problem in their communities, with 9 in 10 (89.6%) indicating that they agree or strongly agree. More than three-fourths (87.5%) indicated support for reclassifying gabapentin as a CS. Common reasons for opposition to gabapentin regulatory changes were that they would not reduce or eliminate abuse (45.8%) and that they would be an inconvenience to patients (17.0%). Pharmacists practicing in independent pharmacies and pharmacists in practice greater than 20 years were less likely to indicate support for gabapentin reclassification.

CONCLUSION

Kentucky community pharmacists express considerable concern over the possible misuse and diversion of gabapentin and widely support regulatory changes reclassifying gabapentin as a CS.

A History of Drug Discovery for Treatment of Nausea and Vomiting and the Implications for Future Research

The origins of the major classes of current anti-emetics are examined. Serendipity is a recurrent theme in discovery of their anti-emetic properties and repurposing from one indication to another is a continuing trend. Notably, the discoveries have occurred against a background of company mergers and changing anti-emetic requirements. Major drug classes include: (i) Muscarinic receptor antagonists-originated from historical accounts of plant extracts containing atropine and hyoscine with development stimulated by the need to prevent sea-sickness among soldiers during beach landings; (ii) Histamine receptor antagonists-searching for replacements for the anti-malaria drug quinine, in short supply because of wartime shipping blockade, facilitated the discovery of histamine (H1) antagonists (e.g., dimenhydrinate), followed by serendipitous discovery of anti-emetic activity against motion sickness in a patient undergoing treatment for urticaria; (iii) Phenothiazines and dopamine receptor antagonists-investigations of their pharmacology as "sedatives" (e.g., chlorpromazine) implicated dopamine receptors in emesis, leading to development of selective dopamine (D2) receptor antagonists (e.g., domperidone with poor ability to penetrate the blood-brain barrier) as anti-emetics in chemotherapy and surgery; (iv) Metoclopramide and selective 5-hydroxytryptamine3(5-HT3) receptor antagonists-metoclopramide was initially assumed to act only via D2 receptor antagonism but subsequently its gastric motility stimulant effect (proposed to contribute to the anti-emetic action) was shown to be due to 5-hydroxytryptamine4 receptor agonism. Pre-clinical studies showed that anti-emetic efficacy against the newly-introduced, highly emetic, chemotherapeutic agent cisplatin was due to antagonism at 5-HT3 receptors. The latter led to identification of selective 5-HT3 receptor antagonists (e.g., granisetron), a major breakthrough in treatment of chemotherapy-induced emesis; (v) Neurokinin1receptor antagonists-antagonists of the actions of substance P were developed as analgesics but pre-clinical studies identified broad-spectrum anti-emetic effects; clinical studies showed particular efficacy in the delayed phase of chemotherapy-induced emesis. Finally, the repurposing of different drugs for treatment of nausea and vomiting is examined, particularly during palliative care, and also the challenges in identifying novel anti-emetic drugs, particularly for treatment of nausea as compared to vomiting. We consider the lessons from the past for the future and ask why there has not been a major breakthrough in the last 20 years.

A novel α-conopeptide Eu1.6 inhibits N-type (CaV2.2) calcium channels and exhibits potent analgesic activity

We here describe a novel α-conopeptide, Eu1.6 from Conus eburneus, which exhibits strong anti-nociceptive activity by an unexpected mechanism of action. Unlike other α-conopeptides that largely target nicotinic acetylcholine receptors (nAChRs), Eu1.6 displayed only weak inhibitory activity at the α3β4 and α7 nAChR subtypes and TTX-resistant sodium channels, and no activity at TTX-sensitive sodium channels in rat dorsal root ganglion (DRG) neurons, or opiate receptors, VR1, KCNQ1, L- and T-type calcium channels expressed in HEK293 cells. However, Eu1.6 inhibited high voltage-activated N-type calcium channel currents in isolated mouse DRG neurons which was independent of GABA_B receptor activation. In HEK293 cells expressing Ca_V2.2 channels alone, Eu1.6 reversibly inhibited depolarization-activated Ba²⁺ currents in a voltage- and state-dependent manner. Inhibition of Ca_V2.2 by Eu1.6 was concentration-dependent (IC₅₀ ~1 nM). Significantly, systemic administration of Eu1.6 at doses of 2.5–5.0 μg/kg exhibited potent analgesic activities in rat partial sciatic nerve injury and chronic constriction injury pain models. Furthermore, Eu1.6 had no significant side-effect on spontaneous locomotor activity, cardiac and respiratory function, and drug dependence in mice. These findings suggest α-conopeptide Eu1.6 is a potent analgesic for the treatment of neuropathic and chronic pain and opens a novel option for future analgesic drug design.

Cannabinoid Hyperemesis Syndrome and the Consulting Psychiatrist: A Case Study of Diagnosis and Treatment for an Emerging Disorder in Psychiatric Practice

The increasing prevalence of cannabis use in the United States requires awareness of cannabis-related disorders and familiarity with treatment options. We present a case of cannabinoid hyperemesis syndrome that required psychiatric consultation for diagnostic clarification and effective treatment with intravenous haloperidol. Literature from emergency medicine, toxicology, and gastroenterology is reviewed, including proposed diagnostic criteria for cannabinoid hyperemesis syndrome and reported off-label treatment options, with a specific focus on clinical questions facing the practicing psychiatrist regarding this emerging disorder.

The Effect of Preoperative Pregabalin on Postoperative Nausea and Vomiting: A Meta-analysis

BACKGROUND

Nonopioid adjuvant medications are increasingly included among perioperative Enhanced Recovery After Surgery protocols. Preoperative pregabalin has been shown to improve postoperative pain and limit reliance on opioid analgesia. Our group investigated the ability of preoperative pregabalin to also prevent postoperative nausea and vomiting (PONV).

METHODS

Our group performed a meta-analysis of randomized trials that report outcomes on the effect of preoperative pregabalin on PONV endpoints in patients undergoing general anesthesia.

RESULTS

Among all included trials (23 trials; n = 1693), preoperative pregabalin was associated with a significant reduction in PONV (risk ratio [RR] = 0.53; 95% confidence interval [CI], 0.39-0.73; P = 0.0001), nausea (RR = 0.62; 95% CI, 0.46-0.83; P = 0.002), and vomiting (RR = 0.68; 95% CI, 0.52-0.88; P = 0.003) at 24 hours. Subgroup analysis designed to account for major PONV confounders, including the exclusion trials with repeat dosing, thiopental induction, nitrous oxide maintenance, and prophylactic antiemetics and including high-risk surgery, resulted in similar antiemetic efficacy. Preoperative pregabalin is also associated with significantly increased rates of postoperative visual disturbance (RR = 3.11; 95% CI, 1.34-7.21; P = 0.008) compared with a control.

CONCLUSIONS

Preoperative pregabalin is associated with significant reduction of PONV and should not only be considered as part of a multimodal approach to postoperative analgesia but also for prevention of PONV.

Combination of gabapentin and ramosetron for the prevention of postoperative nausea and vomiting after gynecologic laparoscopic surgery: a prospective randomized comparative study

Background

As a drug originally introduced for its anticonvulsant effects, gabapentin has been recently shown to be effective in the treatment of nausea and vomiting in various clinical settings. This study compared the antiemetic efficacy of oral gabapentin, intravenous ramosetron and gabapentin plus ramosetron in patients receiving fentanyl-based patient-controlled analgesia after laparoscopic gynecologic surgery.

Methods

One hundred and thirty two patients undergoing laparoscopic gynecologic surgery under general anesthesia were allocated randomly into three groups: group G received 300 mg oral gabapentin 1 h before anesthesia, group R received 0.3 mg intravenous ramosetron at the end of surgery, and group GR received a combination of 300 mg oral gabapentin 1 h before anesthesia and 0.3 mg intravenous ramosetron at the end of surgery. Postoperative nausea, retching, vomiting, rescue antiemetic drug use, pain, rescue analgesic requirements and adverse effects were assessed at 0–2, 2–24 and 24–48 h after surgery. Postoperative nausea and vomiting (PONV) was defined as the presence of nausea, retching or vomiting.

Results

The incidence of complete response (no PONV and no rescue antiemetics up to 48 h postoperatively) was significantly higher in group GR (26/40, 65%) than group G (16/40, 40%; P = 0.025) and group R (18/44, 41%; P = 0.027), whereas there was no significant difference between group G and group R (P = 0.932). There were no significant between-group differences in the incidence of emetic episodes, use of rescue antiemetics, severe emesis, use of rescue analgesics or any adverse effects. Postoperative pain scores were also similar among groups.

Conclusions

The combination with gabapentin and ramosetron is superior to either drug alone for prevention of PONV after laparoscopic gynecologic surgery.

Trial registration

ClinicalTrials.gov NCT02617121, registered November 25, 2015.

The comparative preemptive analgesic efficacy of addition of vitamin B complex to gabapentin versus gabapentin alone in women undergoing cesarean section under spinal anesthesia: A prospective randomized double-blind study

BACKGROUND

Development of new multimodal analgesic regimens have led to substantial improvement in postoperative pain relief. We designed this study to compare the effect of combined vitamin B complex-gabapentin versus gabapentin alone on postoperative pain in women undergoing cesarean section under spinal anesthesia.

METHODS

One hundred twenty-eight women who underwent cesarean section under spinal anesthesia were randomized to receive orally 300 mg gabapentin (group G) or 300 mg of gabapentin plus 2 vitamin B complex (group GB) tablets 30 minutes before surgery. Postoperative pain intensity and total analgesic consumption during 12 hours after surgery, vomiting, and drowsiness during recovery were assessed.

RESULTS

The pain intensity in the gabapentin plus vitamin B complex group was lower than gabapentin group during 12 hours after surgery (95% CI: 1.4-2.2; P < .001). Meanwhile, the total analgesic consumption in this group was less than gabapentin alone (95% CI: 1.07-1.24; P = 0.034). The incidence of vomiting in patients who receive combined gabapentin-vitamin B complex group was similar to gabapentin alone (P = .206). The difference of the distribution of the relative frequency of sedation according to Ramsay sedation scores in patients between 2 groups were insignificant (P = .82). All newborns in our study were free of any adverse effects.

CONCLUSION

Addition of vitamin B complex to gabapentin reduced intensity of postoperative pain and also the total amount of analgesic consumption within the first 12 hours postoperative following cesarean section.

Central Aspects of Nausea and Vomiting in GI Disorders

OPINION STATEMENT

Nausea and vomiting result from continuous interactions among gastrointestinal, central nervous system, and autonomic nervous system. Despite being closely associated, central pathways of nausea and vomiting appear to be at least partly different and nausea is no longer considered only a penultimate step of vomiting. Although our understanding of central pathways of nausea has improved over the last one decade, it is still very basic. Afferent pathways from gastrointestinal tract via vagus, vestibular system, and chemoreceptor trigger zone project to nucleus tractus solitarius which, in turn, relays the signal to central pattern generator initiating multiple downstream pathways. This central nausea pathway appears to be under constant modulation by autonomic nervous system and cerebral cortex. There is also some evidence that central pathway of chronic nausea is different from that of acute nausea and closely resembles that of neuropathic pain. This improved understanding has modified the way we can approach the treatment of acute and chronic nausea. While conventional therapies such as antiemetics (antiserotoninergic, antihistaminic, antidopaminergic) and prokinetics are commonly used to manage acute nausea, they are not as effective in improving chronic nausea. Recently, neuromodulators such as tricyclic antidepressants, gabapentin, olanzapine, benzodiazepines, and cannabinoids have been shown to have antinausea effect. There is a need to study the utility of these drugs in managing chronic functional nausea. Improving our understanding of central and peripheral circuitry of nausea will allow us to better utilize the currently available drugs and develop new therapeutic options.

The Effect of Preoperative Gabapentin on Postoperative Nausea and Vomiting: A Meta-Analysis

BACKGROUND

Preoperative gabapentin has been shown to improve postoperative pain and limit reliance on opioid analgesia. On the basis of an alternative mechanism, our group investigated the ability of preoperative gabapentin to prevent postoperative nausea and vomiting (PONV).

METHODS

We performed a meta-analysis of trials that reported outcomes on the effect of preoperative gabapentin on PONV end points in patients undergoing general anesthesia. In our primary analysis, we calculated the pooled antiemetic effects of preoperative gabapentin in studies with PONV as the primary end point. In our secondary analysis, we calculated the pooled effects in trials involving preoperative gabapentin that reported on the side effects, nausea and vomiting.

RESULTS

Among the trials designed with PONV as a primary end point (8 trials; n = 838), preoperative gabapentin was associated with a significant reduction in PONV (risk ratio [RR] = 0.60; 99% confidence interval [CI], 0.50-0.72; P < 0.0001), nausea (RR = 0.34; 99% CI, 0.20-0.56; P < 0.0001), and vomiting (RR = 0.34; 99% CI, 0.19-0.61; P = 0.0002) at 24 hours. Among all included trials (44 trials; n = 3489) that reported on the side effects, nausea and vomiting, similar reductions were noted in PONV with preoperative gabapentin administration. Subgroup analysis of trials excluding repeat dosing, thiopental induction, and nitrous oxide maintenance and including high-risk surgery resulted in similar PONV efficacy. Preoperative gabapentin is also associated with significantly increased rates of postoperative sedation (RR = 1.22; 95% CI, 1.02-1.47; P = 0.03) compared with control.

CONCLUSIONS

Preoperative gabapentin is associated with a significant reduction in PONV among studies designed to investigate this end point. Preoperative gabapentin should be considered not only as part of a multimodal approach to postoperative analgesia, but also for prevention of PONV.

Nausea: a review of pathophysiology and therapeutics

The sensation of nausea is a common occurrence with diverse causes and a significant disease burden. Nausea is considered to function as a protective mechanism, warning the organism to avoid potential toxic ingestion. Less adaptive circumstances are also associated with nausea, including post-operative nausea, chemotherapy-induced nausea, and motion sickness. A common definition of nausea identifies the symptom as a precursor to the act of vomiting. The interaction, though present, does not appear to be a simple relationship. Nausea is unfortunately the 'neglected symptom', with current accepted therapy generally directed at improving gastrointestinal motility or acting to relieve emesis. Improved understanding of the pathophysiological basis of nausea has important implications for exploiting novel mechanisms or developing novel therapies for nausea relief.

Gabapentin prophylaxis for postoperative nausea and vomiting in abdominal surgeries: a quantitative analysis of evidence from randomized controlled clinical trials

INTRODUCTION

Postoperative nausea and vomiting (PONV) is frequently encountered in the surgical recovery room. Abdominal surgery is one important risk factor for increased incidence of PONV. Gabapentin, an anticonvulsant with known postoperative analgesic properties, has shown some activity against PONV. Results from clinical trials evaluating the anti-emetic efficacy of gabapentin are conflicting. The present meta-analysis was performed to examine this issue.

METHODS

Seventeen randomized placebo-controlled trials reporting PONV with preoperative gabapentin administration in patients undergoing abdominal surgery were included for analysis. Outcomes evaluated were nausea, vomiting, composite PONV and the use of rescue anti-emetic medication in the postoperative period.

RESULTS

The pooled relative risk (RR), estimated using the random effects model of the metafor package for R, was 0.76 (95% CI 0.58-0.98) for nausea, 0.62 (0.45-0.85) for vomiting, 0.71 (0.39-1.28) for data represented as composite PONV (possibly biased by a single study, as observed in the sensitivity analysis), and 0.6 (0.41-0.89) for rescue anti-emetic use. There was a significant RR reduction for nausea and vomiting when propofol was not used as induction and/or maintenance for anaesthesia. In the abdominal hysterectomy subgroup, there was a significant RR reduction for vomiting but not for nausea.

DISCUSSION

The present analysis provides evidence supporting preoperative gabapentin as a pharmacotherapy for prevention of PONV in patients undergoing abdominal surgeries. Future studies comparing preoperative gabapentin with 5HT3 antagonists are needed to precisely define its role in PONV.

Potential maternal symptomatic benefit of gabapentin and review of its safety in pregnancy

Restless legs syndrome (RLS) and nausea and vomiting of pregnancy (NVP) are both common maternal conditions affecting quality of life. Gabapentin is currently FDA-approved for treating RLS and preliminary results have shown it may be effective for treating the most severe form of NVP, hyperemesis gravidarum (HG). Because NVP and HG symptoms peak early in pregnancy, the potential teratogenicity of gabapentin needs to be considered. We reviewed published pregnancy registries and cohorts for pregnancy outcomes associated with maternal gabapentin use. Gabapentin exposures from 5 pregnancy registries, 1 HG pilot study and 2 additional cases were reviewed. Among 294 first trimester gabapentin-monotherapy exposures, there were 5 major congenital malformations (MCMs) reported (1.7%), which favorably compares to the MCM rate in the general population (1.6-2.2%). Two of the registries reported maternal gabapentin use among 261 singleton pregnancies to be associated with roughly equivalent rates of premature birth, birth weight after correction for gestational age at delivery and maternal hypertension/eclampsia as those that have been reported in the general population. These data support the safety of gabapentin use in pregnancy; however, the number of exposures to date is still small. If future pregnancy registry data confirm this positive safety profile, gabapentin therapy would likely be a safe and effective treatment for RLS during pregnancy. Controlled, clinical trials are needed to assess gabapentin's effectiveness for HG.