AnticonvulsantUS FDA Database Verified

vigabatrin (Rx)

Generic: Vigabatrin

Brand: Sabril

(vye-ga'ba-trin)

Pregnancy Category: C

Pharmacological Action

May inhibit reuptake and metabolism of GABA, may increase seizure threshold; structurally similar to GABA

Therapeutic outcome: Prevention of seizure activity

Uses

Adjunct treatment of partial seizures in adults and children ≥ 12 yr, infantile spasm

Contraindications

Hypersensitivity to this product

BLACK BOX WARNING: Visual disturbance

Precautions: Pregnancy C, breastfeeding, children < 2 yr, geriatric patients, renal/hepatic disease, suicidal ideation/behavior, abrupt discontinuation

Dosage & Routes

Partial seizures

Adult: PO 500 mg bid, titrate in 500-mg increments at weekly intervals, up to 1.5 g bid Infantile spasm Infant > 1 mo, child ≤ 2 yr: PO 50 mg/kg/day in 2 divided doses titrate in 25-50 mg/kg/day increments q3 days, max 150 mg/kg/day Renal dose

Adult: PO CCr 50-80 ml/min, reduce dosage by 25%; PO CCr 30-50 ml/min, reduce dosage by 50%; PO CCr 10-30 ml/min, reduce dosage by 75%

Available forms: Powder for oral sol 500 mg; tablet 500 mg

Implementation PO route (tab) - Give without regard to meals PO route (oral solution) - Reconstitute immediately before using - Empty contents of appropriate number of packets into a clean cup - For each packet, dissolve 10 ml of water, conc. 50 mg/ml; do not use other liquids - Stir until dissolved; solution should be clear - Use calibrated oral syringe to measure correct dosage - Discard any unused solution

Adverse Effects

CNS: Headache, memory impairment, dizziness, irritability, lethargy, malignant hyperthermia, insomnia, suicidal ideation

CV: Edema

EENT: Vision impairment

GI: Nausea, vomiting, diarrhea, increased appetite, abdominal pain, GI bleeding, hemorrhoids, weight gain, constipation

GU: Impotence, dysmenorrhea

HEMA: Anemia

INTEG: Pruritus, rash

RESP: Coughing, respiratory depression, pulmonary embolism

Pharmacokinetics

Absorption: > 95%

Distribution: Widely; no protein binding

Metabolism: Not metabolized

Excretion: Urine 80% parent drug, slowed in renal disease

Half-life: 7.5 hr

Pharmacodynamics

Onset: Unknown

Peak: 2 hr

Duration: Unknown

Interactions

Individual drugs AzaTHIOprine, chloroquine, deferoxamine, ethambutol, hydroxychloroquine, interferons, loxapine, mecasermin, rh-IGF-1, pentostatin, tamoxifen, thiothixene: increased serious ophthalmic effects (glaucoma, retinopathy); avoid concurrent use

Drug classifications CNS depressants: increased CNS depression Corticosteroids, phenothiazines, phosphodiesterase inhibitors: increased serious ophthalmic effects (glaucoma, retinopathy)

Drug/lab test

Decreased: ALT/AST

Nursing Considerations

Assessment - Visual impairment: prescribers must be registered with the SHARE program due to risk of permanent vision loss; if no clinical response in 2-4 wk in pediatric patients or 3 mo in adults, provide vision assessment; assess again after ≤ 4 wk, at least q3 mo, and 3-6 mo after stopping product - Monitor renal studies: urinalysis, BUN, urine creatinine q3 mo in those with renal disease - Monitor hepatic studies: ALT, AST, bilirubin - Assess description of seizures: location, duration, presence of aura - Assess mental status: mood, sensorium, affect, behavioral changes; if mental status changes, notify prescriber Perform/provide - Store at room temperature - Provide assistance with ambulation during early part of treatment; dizziness occurs - Provide seizure precautions: padded side rails; move objects that may harm patient

Patient/family education - Teach patient to carry emergency ID stating patient’s name, products taken, condition, prescriber’s name and phone number - Advise patient to avoid driving, other activities that require alertness - Inform patient not to discontinue medication quickly after long-term use - Instruct patient to notify prescriber if pregnancy is planned or suspected - Instruct patient to report suicidal thoughts/behaviors immediately - Instruct patient to avoid alcohol; drowsiness, dizziness may occur

Evaluation

Positive therapeutic outcome: Decreased seizure activity; document on patient’s chart

Reference

Mosby's Drug Guide; Davis Drug Guide

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