vye-GAH-bat-rin

Therapeutic Classification: anticonvulsants

• Refractory complex partial seizures in patients who have responded inadequately to several alternative treatments (and where potential benefits outweigh the risk of vision loss) (as adjunctive therapy).
• Infantile spasms in patients in whom potential benefits outweigh the risk of vision loss.

• Acts an irreversible inhibitor of -aminobutyric acid transaminase (GABA-T), the enzyme responsible for the metabolism of the inhibitory neurotransmitter GABA. This action results in increased levels of GABA in the central nervous system.

• Decreased incidence and severity of refractory complex partial seizures.
• Decreased incidence of spasms in infants.

Absorption: Completely absorbed following oral administration.

Distribution: Enters breast milk, remainder of distribution unknown.

Metabolism/Excretion: Minimal metabolism, mostly eliminated unchanged in urine.

Half-life: 7.5 hr.

(anticonvulsant effect)

†blood level.

†clinical benefit should be seen in 2–4 wk for IS or within 3 mo for complex partial seizures.

Contraindicated in:

• History or high risk of other types of irreversible vision loss unless benefits of treatment clearly outweigh risks
• Lactation: Lactation.

Use Cautiously in:

• Renal impairment (↓ dose if CCr <50 mL/min)
• History of suicidal ideation
• OB: Use during pregnancy only if the potential maternal benefit justifies the potential fetal risk
• Pedi: Abnormal MRI signal changes have been seen in infants
• Geri: Consider age-related ↓ in renal function (↑ risk of sedation/confusion).

CV: edema.

Derm: STEVENS-JOHNSON SYNDROME (SJS), TOXIC EPIDERMAL NECROLYSIS (TEN).

EENT: blurred vision, nystagmus, vision loss, tunnel vision.

Hemat: anemia.

Metab: weight gain.

MS: arthralgia.

Neuro: abnormal coordination, confusion, drowsiness, fatigue, memory impairment, tremor, INTRAMYELINIC EDEMA, peripheral neuropathy, SUICIDAL THOUGHTS.

Drug-Drug:

• Should not be used concurrently with other drugs having adverse ocular effects; ↑ risk of additive toxicity.
• May ↓ phenytoin levels and effectiveness.

Refractory Complex Partial Seizures

• PO (Adults and Children 17 yr): 500 mg twice daily initially; may ↑ in 500-mg increments every 7 days, depending on response, up to 1500 mg twice daily.
• PO (Children 2–16 yr and >60 kg): 500 mg twice daily initially; may ↑ in 500-mg increments every 7 days, depending on response, up to 1500 mg twice daily.
• PO (Children 2–16 yr and 26–60 kg): 250 mg twice daily initially; may ↑ every 7 days, depending on response, up to 1000 mg twice daily.
• PO (Children 2–16 yr and 21–25 kg): 250 mg twice daily initially; may ↑ every 7 days, depending on response, up to 750 mg twice daily.
• PO (Children 2–16 yr and 16–20 kg): 225 mg twice daily initially; may ↑ every 7 days, depending on response, up to 650 mg twice daily.
• PO (Children 2–16 yr and 10–15 kg): 175 mg twice daily initially; may ↑ every 7 days, depending on response, up to 525 mg twice daily.

Infantile Spasms

• PO (Children 1 mo–2 yr): 25 mg/kg twice daily initially; may be ↑ by 25–50 mg/kg/day increments every 3 days up to a maximum of 150 mg/kg/day (75 mg/kg twice daily); dosage adjustments are necessary for renal impairment.

(Generic available)

• Tablets: 500 mg;
• Powder for oral solution: 500 mg/pkt;

• Assess location, duration, and characteristics of seizure activity. Institute seizure precautions. Assess response to and continued need for vigabatrin periodically during therapy.
• Monitor closely for notable changes in behavior that could indicate the emergence or worsening of suicidal thoughts or behavior or depression.
• Test vision at baseline (no later than 4 wk after starting), at least every 3 mo during, and 3–6 mo after discontinuation of therapy. Vision loss is irreversible and may not be noticed by patient or caregiver until severe; consider discontinuation of therapy if vision loss occurs. Vision loss may continue after discontinuation of therapy. Risk of vision loss increases with dose and cumulative exposure.
• Assess for signs and symptoms of peripheral neuropathy (numbness or tingling or toes or feet, reduced lower limb vibration or position sensation, progressive loss of reflexes, starting at ankles).
• Assess for rash periodically during therapy. May cause SJS or TEN. Discontinue therapy if severe or if accompanied with fever, general malaise, fatigue, muscle or joint aches, blisters, oral lesions, conjunctivitis, hepatitis, and/or eosinophilia.

• Monitor CBC periodically during therapy. May cause anemia.
  • May cause ↓ AST and ALT levels precluding use to detect hepatic injury.
  • May ↑ amino acids in urine causing false positive results of genetic metabolic diseases.

• Do not confuse vigabatrin with dabigatran.
• Available only through Vigabatrin REMS program of restricted distribution. Only prescribers and pharmacies registered in the program and patients enrolled in the program have access. Patients receive vigabatrin from a specialty pharmacy. Further information is available at , or call 1-866-244-8175.
• PO: Administer twice daily without regard to food.
  • Mix oral solution for babies by mixing each 500 mg packet with 10 mL of water for a concentration of 50 mg/mL; may be cold or room temperature. Solution is clear and colorless; do not administer solutions that are discolored or contain particulate matter. Follow manufacturer's instruction for mixing oral solution. Administer resulting solution using the 3 mL or 10 mL oral syringe provided by the pharmacy. Oral solution may be administered at the same time as food but should only be mixed with water.

• Enroll patient in Vigabatrin REMS Program. Instruct patient to take vigabatrin around the clock, as directed. Discuss with health care professional what to do if a dose is missed. Medication should be gradually discontinued to prevent seizures. Advise patient to read the Medication Guide before starting therapy and with each Rx refill in case of changes.
• Educate patient on risks of vigabatrin. Inform patient of the risk of permanent vision loss, particularly loss of peripheral vision, and that vision loss may not be detected before it is severe and is irreversible. Emphasize the importance of monitoring vision every 3 mo. Advise patient to notify health care professional immediately if changes in vision (not seeing as well as before starting therapy, tripping, bumping into things, more clumsy than usual, surprised by people or things coming in front of you that seem to come out of nowhere) or changes in infant's vision are suspected.
• May cause drowsiness, ataxia, fatigue, and confusion. Caution patient to avoid driving or other activities requiring alertness until response to medication is known. Tell patient not to resume driving until physician gives clearance based on control of seizure disorder.
• Inform patients and families of risk of suicidal thoughts and behavior and advise that behavioral changes, emergency or worsening signs and symptoms of depression, unusual changes in mood, or emergence of suicidal thoughts, behavior, or thoughts of self-harm or rash should be reported to health care professional immediately.
• Advise patient to notify health care professional if an increase in seizures, weight gain, or edema occurs or if sleepiness, ear infection, or irritability occurs in an infant.
• Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken, to consult health care professional before taking any new medications and to avoid taking alcohol or other CNS depressants concurrently with vigabatrin
• May cause fetal harm. Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected and to avoid breastfeeding during therapy. Encourage pregnant patients to enroll in the North American Antiepileptic Drug Pregnancy Registry by calling 1-888-233-2334; information is available at . This must be done by the patient herself.

• Decreased seizure activity. If no substantial clinical benefit within 3 mo of initiation, discontinue vigabatrin.
• Decreased in infantile spasms. If no substantial clinical benefit within 2–4 wk of initiation, discontinue vigabatrin.

Sabril, Vigadrone