Horizant Side Effects
Generic Name: gabapentin enacarbil
Note: This page contains information about the side effects of gabapentin enacarbil. Some of the dosage forms included on this document may not apply to the brand name Horizant.
Not all side effects for Horizant may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.
For the Consumer
Applies to gabapentin enacarbil: extended-release tablets
Check with your doctor if any of these most COMMON side effects persist or become bothersome:
Seek medical attention right away if any of these SEVERE side effects occur while taking gabapentin enacarbil (the active ingredient contained in Horizant)
Dizziness; drowsiness; dry mouth; gas; headache; increased appetite; nausea; tiredness; trouble sleeping; weakness; weight gain.
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision; confusion; loss of balance or coordination; new or worsening mental, mood, or behavioral changes (eg, depression, agitation, anxiety, panic attacks, aggressiveness, impulsiveness, irritability, hostility, exaggerated feeling of well-being, restlessness, inability to sit still); new or worsening trouble sleeping; suicidal thoughts or actions; swelling of the hands, legs, or feet.
For Healthcare Professionals
Applies to gabapentin enacarbil: compounding powder, oral capsule, oral solution, oral tablet, oral tablet extended release
Nervous system side effects have been common. Somnolence, dizziness, ataxia, headache, and fatigue have been reported to occur in more than 10% of treated patients. Vertigo, hyperkinesia, paresthesia, decreased or absent reflexes, increased reflexes, anxiety, and hostility have been reported frequently. CNS tumors, syncope, dreaming abnormal, aphasia, hypesthesia, intracranial hemorrhage, hypotonia, dysesthesia, paresis, dystonia, hemiplegia, facial paralysis, stupor, cerebellar dysfunction, positive Babinski sign, decreased position sense, subdural hematoma, apathy, hallucination, decrease or loss of libido, agitation, paranoia, depersonalization, euphoria, feeling high, doped-up sensation, suicide attempt, and psychosis have been reported infrequently. Choreoathetosis, orofacial dyskinesia, encephalopathy, nerve palsy, personality disorder, increased libido, subdued temperament, apraxia, fine motor control disorder, meningismus, local myoclonus, hyperesthesia, hypokinesia, mania, neurosis, hysteria, antisocial reaction, and suicide have been reported rarely. Nystagmus, tremor, nervousness, amnesia, dysarthria and depression have also been reported. A small number of cases of absence status and status epilepticus have occurred in patients taking gabapentin. Cases of delirium tremens have been reported upon gabapentin withdrawal.[Ref]
Gastrointestinal side effects have been reported in one to three percent of treated patients. Anorexia, flatulence, and gingivitis have been reported frequently. Glossitis, gum hemorrhage, thirst, stomatitis, increased salivation, gastroenteritis, hemorrhoids, bloody stools, and fecal incontinence have been reported infrequently. Dysphagia, eructation, pancreatitis, peptic ulcer, colitis, blisters in mouth, tooth discoloration, salivary gland enlarged, lip hemorrhage, esophagitis, hiatal hernia, hematemesis, proctitis, irritable bowel syndrome, rectal hemorrhage, and esophageal spasm have been reported rarely. Dyspepsia, dry mouth, constipation, dental abnormalities, flatulence, increased appetite, breast enlargement, and weight gain have also been reported.[Ref]
Other side effects have been reported to include withdrawal effects. Withdrawal of gabapentin therapy has been reported to cause the following effects in less than 2% of treated patients: somnolence, ataxia, fatigue, nausea, vomiting, and dizziness.
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, and labyrinthitis have also been reported.
Other side effects reported postmarketing have included angioedema, blood glucose fluctuation, breast enlargement, elevated creatine kinase, elevated liver function tests, erythema multiforme, fever, hyponatremia, jaundice, movement disorder, and Stevens-Johnson syndrome.[Ref]
Hematologic side effects have frequently been reported to include purpura. Anemia, thrombocytopenia, and lymphadenopathy have been reported infrequently. Increased WBC count, lymphocytosis, non-Hodgkin's lymphoma, and increased bleeding time have been reported rarely. Isolated cases of decreased white blood cell counts have also been reported.[Ref]
The patients reported to have decreased white blood cell counts were also taking carbamazepine.[Ref]
Cardiovascular side effects including hypertension have been reported to occur in more than one percent of patients taking gabapentin. Hypotension, angina pectoris, peripheral vascular disorder, palpitation, tachycardia, and murmur have been reported infrequently. Atrial fibrillation, heart failure, thrombophlebitis, deep thrombophlebitis, myocardial infarction, cerebrovascular accident, pulmonary thrombosis, ventricular extrasystoles, bradycardia, premature atrial contraction, pericardial rub, heart block, pulmonary embolus, hyperlipidemia, hypercholesterolemia, pericardial effusion, and pericarditis have been reported rarely. A case of gabapentin induced edema has also been reported.[Ref]
Ocular side effects including abnormal vision have been reported frequently. Cataract, conjunctivitis, dry eyes, eye pain, visual field defect, photophobia, bilateral or unilateral ptosis, eye hemorrhage, hordeolum, eye twitching, diplopia and blurred vision have been reported infrequently. Eye itching, abnormal accommodation, eye focusing problem, watery eyes, retinopathy, glaucoma, iritis, corneal disorders, lacrimal dysfunction, degenerative eye changes, blindness, retinal degeneration, miosis, chorioretinitis, and strabismus have been reported rarely. A case of oculogyric crisis has also been reported.[Ref]
Psychiatric side effects including two cases of intolerable aggressive behavior have been reported. One case of hypomania has also been reported.[Ref]
Dermatologic side effects including alopecia, eczema, dry skin, increased sweating, urticaria, hirsutism, seborrhea, cyst, and herpes simplex have been reported infrequently. Herpes zoster, skin discolor, skin papules, photosensitive reaction, leg ulcer, scalp seborrhea, psoriasis, desquamation, maceration, skin nodules, subcutaneous nodule, melanosis, skin necrosis, and local swelling have been reported rarely. One case of alopecia and one case of leukocytoclastic vasculitis have been reported.[Ref]
Hypersensitivity side effects including a case of hypersensitivity syndrome have been reported.[Ref]
Genitourinary side effects including hematuria, dysuria, urination frequency, cystitis, urinary retention, urinary incontinence, vaginal hemorrhage, amenorrhea, dysmenorrhea, menorrhagia, breast cancer, inability to climax, and abnormal ejaculation have been reported infrequently. Kidney pain, leukorrhea, pruritus genital, renal stone, acute renal failure, anuria, glycosuria, nephrosis, nocturia, pyuria, urination urgency, vaginal pain, breast pain, and testicle pain have been reported rarely.[Ref]
Musculoskeletal side effects including arthralgia have been reported frequently. Tendinitis, arthritis, joint stiffness, joint swelling, and positive Romberg test have been reported infrequently. Costochondritis, osteoporosis, bursitis, and contracture have been reported rarely. Myoclonus has also been reported. Postmarketing reports have included rhabdomyolysis and elevated creatine kinase.[Ref]
General side effects have included asthenia, malaise, and facial edema which have been reported frequently. Generalized edema, weight decrease, and chill have been reported infrequently. Lassitude, "strange feelings", alcohol intolerance, and hangover effect have been reported rarely.[Ref]
Endocrine side effects including hyperthyroid, hypothyroid, swollen testicle, goiter, hypoestrogenism, ovarian failure, epididymitis, and cushingoid appearance have been reported rarely. Endocrine side effects reported postmarketing have included breast enlargement.
Respiratory side effects including pneumonia have been reported frequently. Epistaxis, dyspnea, and apnea have been reported infrequently. Mucositis, aspiration pneumonia, hyperventilation, hiccup, laryngitis, nasal obstruction, snoring, bronchospasm, hypoventilation, and lung edema have been reported rarely.
Hepatic side effects including hepatomegaly have been reported infrequently. Several cases of hepatotoxicity have also been reported.[Ref]
Male rats receiving doses of gabapentin of up to 2000 mg/kg for 2 years have developed acinar cell carcinoma of the pancreas.[Ref]
Oncologic side effects have been reported in animal studies.[Ref]
Renal side effects including two cases of marked increase in serum creatinine measurements following the introduction of gabapentin have been reported.[Ref]
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