What the label lists and what reports show
Gabapentin enacarbil side effects
Gabapentin enacarbil's FDA label: “Most common adverse reactions (≥10% and at least 2 times the rate of placebo) were somnolence/sedation and dizziness.” FAERS holds 2,830 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is toxicity to various agents (594 reports).
- No generic listed
Check it at the source: the gabapentin enacarbil FDA label on DailyMed (effective April 28, 2025, Azurity Pharmaceuticals, Inc. (formerly Arbor Pharmaceuticals)); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of HORIZANT?See " What is the most important information I should know about HORIZANT? " The most common side effects of HORIZANT include: sleepiness dizziness headache Tell your healthcare provider if you have any side effect that bothers you or that does not go away. These are not all the possible side effects of HORIZANT. For more information, ask your healthcare provider or pharmacist. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
Source: FDA drug label, Azurity Pharmaceuticals, Inc. (formerly Arbor Pharmaceuticals), effective April 28, 2025 (SPL set 4c486fc7-c8c4-4c6c-b30c-366dabaeaadd), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (≥10% and at least 2 times the rate of placebo) were somnolence/sedation and dizziness.
Table 4. Incidence of Adverse Reactions in 12-Week RLS Studies Reported in ≥2% of Patients Treated With 600 or 1,200 mg of HORIZANT and Numerically Greater Than Placebo
| Body System/Adverse Reaction | Placebo a (N = 245) % | HORIZANT 600 mg/day b (N = 163) % | HORIZANT 1,200 mg/day c (N = 269) % |
|---|---|---|---|
| Somnolence/sedation | 6 | 20 | 27 |
| Dizziness | 4 | 13 | 22 |
| Headache | 11 | 12 | 15 |
| Nausea | 5 | 6 | 7 |
| Dry mouth | 2 | 3 | 4 |
| Flatulence | <1 | 3 | 2 |
| Fatigue | 4 | 6 | 7 |
| Irritability | 1 | 4 | 4 |
| Feeling drunk | 0 | 1 | 3 |
| Feeling abnormal | <1 | <1 | 3 |
| Peripheral edema | 1 | <1 | 3 |
| Weight increased | 2 | 2 | 3 |
| Increased appetite | <1 | 2 | 2 |
| Vertigo | 0 | 1 | 3 |
| Depression | <1 | <1 | 3 |
| Libido decreased | <1 | <1 | 2 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are described in more detail in the Warnings and Precautions section of the labeling: Effects on Driving [see Warnings and Precautions (5.1) ] Somnolence/Sedation and Dizziness [see Warnings and Precautions (5.2) ] Suicidal Behavior and Ideation [see Warnings and Precautions (5.4) ] Increased Risk of Seizures and Other Adverse Reactions with Abrupt or Rapid Discontinuation [see Warnings and Precautions (5.5) ] Respiratory Depression [see Warnings and Precautions (5.6) ] Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity [see Warnings and Precautions (5.7) ] RLS: Most common adverse reactions (≥10% and at least 2 times the rate of placebo) were somnolence/sedation and dizziness. ( 6.1 ) PHN: Most common adverse reactions (≥10% and greater than placebo) were dizziness, somnolence, and headache. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Azurity Pharmaceuticals, Inc. at 1-800-461-7449 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice. …
Source: FDA drug label, Azurity Pharmaceuticals, Inc. (formerly Arbor Pharmaceuticals), effective April 28, 2025 (SPL set 4c486fc7-c8c4-4c6c-b30c-366dabaeaadd), via openFDA; the full label on DailyMed
What do FAERS reports show?
2,830 reports list gabapentin enacarbil among the medicines taken, each a report of something that happened, not proof the medicine caused it; 700 are coded as a death and 393 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 17 reactions below, 8 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Gabapentin enacarbil: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions