Horizant Side Effects

Generic name: gabapentin enacarbil

Medically reviewed by Drugs.com. Last updated on Oct 28, 2023.

Note: This document provides detailed information about Horizant Side Effects associated with gabapentin enacarbil. Some dosage forms listed on this page may not apply specifically to the brand name Horizant.

Applies to gabapentin enacarbil: oral tablet extended release.

Serious side effects of Horizant

Along with its needed effects, gabapentin enacarbil (the active ingredient contained in Horizant) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking gabapentin enacarbil:

More common

• bloating or swelling of the face, arms, hands, lower legs, or feet
• discouragement
• feeling sad or empty
• irritability
• lack of appetite
• loss of interest or pleasure
• rapid weight gain
• tingling of the hands or feet
• tiredness
• trouble concentrating

Incidence not known

• black, tarry stools
• bloody or cloudy urine
• changes in behavior
• chest pain or discomfort
• chills or fever
• confusion
• difficulty with breathing
• dizziness or lightheadedness
• fainting
• fast heartbeat
• nausea or vomiting
• painful or difficult urination
• rapid, shallow breathing
• rash
• sore throat
• sores, ulcers, or white spots on the lips or in the mouth
• swelling of the face, feet, or lower legs
• swollen, painful, or tender lymph glands in the neck, armpit, or groin
• thoughts of killing oneself
• unusual bleeding or bruising
• upper right abdominal or stomach pain
• yellow eyes and skin

Other side effects of Horizant

Some side effects of gabapentin enacarbil may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• lack or loss of strength
• sleepiness or unusual drowsiness

Less common

• blurred vision
• decreased interest in sexual intercourse
• dry mouth
• excess air or gas in the stomach or intestines
• inability to have or keep an erection
• sensation of spinning
• weight gain

For healthcare professionals

Applies to gabapentin enacarbil: compounding powder, oral capsule, oral solution, oral tablet, oral tablet extended release.

General

The most common adverse reactions associated with the use of this drug were dizziness, somnolence, and peripheral edema.^[Ref]

Nervous system

• Very common (10% or more): Somnolence (21%), dizziness (17%), ataxia (13%)
• Common (1% to 10%): Abnormal gait, incoordination, neuralgia, tremor, dysarthria, hyperkinesia, seizures, dysarthria, paresthesia, hypesthesia, coordination abnormal, increased/decreased/absent reflexes, vertigo
• Uncommon (less than 1%): Hypokinesia
• Rare (less than 0.1%): Movement disorders (e.g., choreoathetosis, dyskinesia, dystonia), loss of consciousness
• Frequency not reported: Withdrawal precipitated seizure/status epilepticus
• Postmarketing reports: Movement disorder^[Ref]

Respiratory

• Common (1% to 10%): Pharyngitis, dyspnea, cough, bronchitis, respiratory infection, rhinitis
• Rare (less than 0.1%): Pulmonary thrombosis, pulmonary embolism
• Frequency not reported: Pseudo-croup, hoarseness
• Postmarketing reports: Respiratory depression^[Ref]

Reports of life-threatening or fatal respiratory depression have been reported in patients taking this drug with CNS depressants including opioids, or in the setting of underlying respiratory impairment.^[Ref]

Hypersensitivity

• Very rare (less than 0.01%): Hypersensitivity syndrome, a systemic reaction with a variable presentation that can include fever, rash, hepatitis, lymphadenopathy, eosinophilia, and sometimes other signs and symptoms
• Frequency not reported: Anaphylaxis, angioedema^[Ref]

Psychiatric

• Common (1% to 10%): Abnormal thinking, amnesia, depression, hostility, confusion, emotional lability, anxiety, nervousness, insomnia
• Uncommon (0.1% to 1%): Mental impairment
• Rare (less than 0.1%): Hallucinations
• Frequency not reported: Suicidal behavior and ideation, hypomania
• Postmarketing reports: Agitation, withdrawal symptoms^[Ref]

There are postmarketing reports of withdrawal symptoms shortly after discontinuing this drug. The most frequently reported reactions with abrupt discontinuation have included anxiety, insomnia, nausea, pain, and sweating. Discontinuation at higher than recommended doses have been associated with agitation, disorientation and confusion. These symptoms have resolved after restarting this drug. The dependence potential of gabapentin has not been evaluated in human studies.^[Ref]

Immunologic

• Frequency not reported: Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)^[Ref]

Dermatologic

• Common (1% to 10%): Abrasion, facial edema, purpura, rash, pruritus, acne
• Uncommon (0.1% to 1%): Alopecia, eczema, dry skin, increased sweating, urticaria, hirsutism, seborrhea, cyst, herpes simplex
• Rare (less than 0.1%): Stevens-Johnson syndrome, angioedema, erythema multiforme, drug rash (with eosinophilia and systemic symptoms), herpes zoster, skin discolor, skin papules, photosensitive reaction, psoriasis, desquamation, maceration, skin nodules, subcutaneous nodule, melanosis, skin necrosis, local swelling
• Frequency not reported: Bullous pemphigoid^[Ref]

Cardiovascular

• Common (1% to 10%): Peripheral edema, vasodilation, hypertension
• Rare (less than 0.1%): Atrial fibrillation, heart failure, myocardial infarction, cerebrovascular accident, ventricular extrasystoles, bradycardia, premature atrial contraction, pericardial rub, heart block, pericardial effusion, pericarditis
• Postmarketing reports: Cardiac arrest, chest pain, palpitation, tachycardia^[Ref]

Endocrine

• Rare (less than 0.1%): Hyperthyroid, hypothyroid, goiter, hypoestrogenism, ovarian failure, epididymitis, cushingoid appearance
• Postmarketing reports: Breast enlargement, breast hypertrophy, gynecomastia^[Ref]

Gastrointestinal

• Common (1% to 10%): Diarrhea, dry mouth or throat, constipation, nausea, vomiting, dyspepsia, dental abnormalities, gingivitis, abdominal pain, flatulence
• Uncommon (0.1% to 1%): Glossitis, gum hemorrhage, thirst, stomatitis, increased salivation, gastroenteritis, hemorrhoids, bloody stools, fecal incontinence
• Rare (less than 0.1%): Pancreatitis, dysphagia, eructation, pancreatitis, peptic ulcer, colitis, blisters in mouth, tooth discoloration, perlèche, salivary gland enlarged, lip hemorrhage, esophagitis, hiatal hernia, hematemesis, proctitis, irritable bowel syndrome, rectal hemorrhage, esophageal spasm
• Frequency not reported: Dehydration^[Ref]

Genitourinary

• Common (1% to 10%): Incontinence, impotence
• Uncommon (0.1% to 1%): Hematuria, dysuria, urinary frequency, cystitis, urinary retention, vaginal hemorrhage, amenorrhea, dysmenorrhea, menorrhagia
• Frequency not reported: Sexual dysfunction (including changes in libido, ejaculation disorders, and anorgasmia)^[Ref]

Hematologic

• Common (1% to 10%): Leucopenia, purpura
• Uncommon (0.1% to 1%): Anemia, lymphadenopathy
• Rare (less than 0.1%): Thrombocytopenia, thrombophlebitis, leukocytosis, lymphocytosis, increased bleeding time
• Frequency not reported: Blood creatine phosphokinase increased, coagulation defect^[Ref]

Hepatic

• Rare (less than 0.1%): Hepatitis, jaundice, elevated liver function tests (AST, ALT), and bilirubin, hepatomegaly, hepatotoxicity^[Ref]

Metabolic

• Common (1% to 10%): Weight gain, hyperglycemia
• Postmarketing reports: Hyponatremia^[Ref]

Musculoskeletal

• Common (1% to 10%): Back pain, arthralgia, myalgia, twitching
• Uncommon (0.1% to 1%): Tendonitis, arthritis, joint stiffness, joint swelling
• Frequency not reported: Rhabdomyolysis, myoclonus
• Postmarketing reports: Elevated creatine kinase, rhabdomyolysis^[Ref]

Ocular

• Common (1% to 10%): Amblyopia, conjunctivitis, diplopia, nystagmus
• Uncommon (0.1% to 1%): Cataract, dry eyes, eye pain, visual field defect, photophobia, bilateral or unilateral ptosis, eye hemorrhage, hordeolum, eye twitching
• Rare (less than 0.1%): Eye itching, abnormal accommodation, eye focusing problem, watery eyes, retinopathy, glaucoma, iritis, corneal disorders, lacrimal dysfunction, degenerative eye changes, blindness, retinal degeneration, miosis, chorioretinitis, strabismus^[Ref]

Oncologic

• Uncommon (0.1% to 1%): Breast cancer
• Rare (less than 0.1%): Non-Hodgkin's lymphoma^[Ref]

Other

• Very common (10% or more): Fatigue (11%), fever (11%)
• Common (1% to 10%): Asthenia, accidental injury, otitis media, tremor, pain
• Rare (0.01% to 0.1%): Tinnitus
• Very rare (less than 0.01%): Sudden unexplained death in patients with epilepsy
• Frequency not reported: Sleepwalking, withdrawal symptoms, hearing loss, earache, tinnitus, inner ear infection, otitis, taste loss, unusual taste, ear fullness, perforated ear drum, sensitivity to noise, eustachian tube dysfunction, otitis externa, odd smell, labyrinthitis^[Ref]

Renal

• Rare (less than 0.1%): Acute renal failure^[Ref]

Frequently asked questions

• Should gabapentin be taken with food?

Further information

Horizant side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer