The most common side effects of gabapentin in adult patients include dizziness, fatigue, drowsiness, weight gain, and peripheral edema (swelling of extremities). Gabapentin may also produce sexual dysfunctionin some patients, symptoms of which may include loss of libido, inability to reach orgasm, and erectile dysfunction. Gabapentin should be used carefully in patients with renal impairment due to possible accumulation and toxicity.
An increase in formation of adenocarcinomas was observed in rats during preclinical trials; however, the clinical significance of these results remains undetermined. Gabapentin is also known to induce pancreatic acinar cell carcinomas in rats through an unknown mechanism, perhaps by stimulation of DNA synthesis; these tumors did not affect the lifespan of the rats and did not metastasize
Gabapentin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- tiredness or weakness
- uncontrollable shaking of a part of your body
- double or blurred vision
- memory problems
- strange or unusual thoughts
- unwanted eye movements
- dry mouth
- increased appetite
- weight gain
- swelling of the hands, feet, ankles, or lower legs
- back or joint pain
- runny nose, sneezing, cough, sore throat, or flu-like symptoms
- ear pain
- red, itchy eyes (sometimes with swelling or discharge)
Some side effects may be serious. If you experience any of the following symptoms, call your doctor immediately:
- swelling of the face, throat, tongue, lips, or eyes
- difficulty swallowing or breathing
Gabapentin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online [at http://www.fda.gov/Safety/MedWatch] or by phone [1-800-332-1088].
In 2009 the U.S. Food and Drug Administration issued a warning of an increased risk of depression and suicidal thoughts and behaviors in patients taking gabapentin, along with other anticonvulsant drugs modifying the packaging insert to reflect this. A 2010 meta analysis confirmed the increased risk of suicide associated with gabapentin use.
Persons who accidentally or intentionally ingested overdoses may have drowsiness, sedation, blurred vision, slurred speech, somnolence and possibly death, if a very high amount was taken, particularly if combined with alcohol. Serum gabapentin concentrations may be measured to confirm diagnosis.