lamotrigine (redirected from Lamictal)

lamotrigine /la·mo·tri·gine/ (lah-mo´tri-jen) an anticonvulsant used in the treatment of certain forms of epilepsy.

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lamotrigine

(lmōt´rijēn´),
n brand name: Lamictal;
drug class: antiepileptic;
action: may be result of blockage of voltage-dependent sodium channels with inhibition of excitatory amino acids;
uses: adjunctive treatment of refractive partial seizures in adults.

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lamotrigine

Lamictal, Lamictal Chewable Dispersible

Pharmacologic class: Phenyltriazine

Therapeutic class: Anticonvulsant

Pregnancy risk category C

FDA Boxed Warning

• Drug has been linked to serious rashes (including Stevens-Johnson syndrome) requiring hospitalization and drug discontinuation; one rash-related death occurred. Rare postmarketing cases of toxic epidermal necrolysis and rash-related death have occurred worldwide. Nearly all cases of life-threatening rashes have arisen within 2 to 8 weeks of treatment initiation. However, isolated cases have been reported after prolonged treatment (such as 6 months). Withdraw drug at first sign of rash, unless rash clearly isn't drug-related. However, know that withdrawal may not prevent rash from becoming life-threatening or permanently disabling or disfiguring.

Action

Unknown. Thought to block sodium channel membranes, which in turn inhibits release of the neurotransmitters glutamate and aspartate in brain.

Availability

Tablets: 25 mg, 100 mg, 150 mg, 200 mg

Tablets (chewable): 2 mg, 5 mg, 25 mg

⊘Indications and dosages

➣ Partial seizures, generalized seizures of Lennox-Gastaut syndrome, and primary generalized tonic-clonic seizures in patients receiving valproate

Adults and children ages 12 and older: 25 mg P.O. every other day during weeks 1 and 2; then 25 mg daily during weeks 3 and 4. Then week 5 onwards to maintenance, increase dosage by 25 to 50 mg/day every 1 to 2 weeks. Usual maintenance dosage is 100 to 400 mg/day in one or two divided doses. For those taking valproate alone, maximum dosage is 200 mg/day.

Children ages 2 to 12: 0.15 mg/kg/day P.O. (rounded down to nearest whole tablet) in one or two divided doses during weeks 1 and 2; then 0.3 mg/kg/day P.O. (rounded down to nearest whole tablet) in one or two divided doses during weeks 3 and 4. Then week 5 onwards to maintenance, increase every 1 to 2 weeks as 0.3 mg/kg/day (rounded down to nearest whole tablet) added to previously administered daily dose. Usual maintenance dosage is 1 to 5 mg/kg/day. Maximum dosage is 200 mg/day in one or two divided doses. For patients taking valproate alone, maintenance dosage is 1 to 3 mg/kg/day. May need to increase maintenance dose by as much as 50% in patients weighing less than 30 kg (66 lb), based on clinical response.

➣ Partial seizures, generalized seizures of Lennox-Gastaut syndrome, and primary generalized tonic-clonic seizures in patients receiving antiepileptic drugs (AEDs) other than carbamazepine, phenytoin, phenobarbital, primidone, or valproate

Adults and children ages 12 and older: 25 mg P.O. every day during weeks 1 and 2; then 50 mg daily during weeks 3 and 4. Increase by 50 mg/day every 1 to 2 weeks. Usual maintenance dosage is 225 to 375 mg/day in two divided doses.

Children ages 2 to 12: 0.3 mg/kg/day P.O. in one or two divided doses (rounded down to nearest whole tablet) during weeks 1 and 2; then 0.6 mg/kg/day P.O. in two divided doses (rounded down to nearest whole tablet) during weeks 3 and 4. Then week 5 onwards to maintenance, increase every 1 to 2 weeks as 0.6 mg/kg/day (rounded down to nearest whole tablet) added to previously administered daily dose. Usual maintenance dosage is 4.5 to 7.5 mg/kg/day (maximum, 300 mg/day) in two divided doses. May need to increase maintenance dose by as much as 50% in patients weighing less than 30 kg, based on clinical response.

➣ Partial seizures, generalized seizures of Lennox-Gastaut syndrome, and primary generalized tonic-clonic seizures in patients receiving carbamazepine, phenytoin, phenobarbital, or primidone, but not receiving valproate

Adults and children ages 12 and older: 50 mg/day P.O. during weeks 1 and 2; then 100 mg/day in two divided doses during weeks 3 and 4. Then week 5 onwards to maintenance, increase by 100 mg/day every 1 to 2 weeks. Usual maintenance dosage is 300 to 500 mg/day in two divided doses.

Children ages 2 to 12: 0.6 mg/kg/day P.O. in two divided doses (rounded down to nearest whole tablet) during weeks 1 and 2; then 1.2 mg/kg/day in two divided doses (rounded down to nearest whole tablet) during weeks 3 and 4. Then week 5 onwards to maintenance, increase every 1 to 2 weeks as 1.2 mg/kg/day (rounded down to nearest whole tablet) added to previously administered daily dose. Usual maintenance dosage is 5 to 15 mg/kg/day (maximum, 400 mg/day) in two divided doses. May need to increase maintenance dose by as much as 50% in patients weighing less than 30 kg, based on clinical response.

➣ Conversion to monotherapy for seizures in patients receiving carbamazepine, phenytoin, phenobarbital, primidone, or valproate as a single agent

Adults and children ages 16 and older: Usual maintenance dosage is 500 mg/day P.O. in two divided doses.

➣ Conversion from carbamazepine, phenytoin, phenobarbital, or primidone to monotherapy with lamotrigine for seizures

Adults and children ages 16 and older: 50 mg/day P.O. during weeks 1 and 2; then 100 mg/day in two divided doses during weeks 3 and 4. Then week 5 onwards to maintenance, increase by 100 mg/day every 1 to 2 weeks. Usual maintenance dosage is 300 to 500 mg/day in two divided doses. After achieving lamotrigine maintenance dosage of 500 mg/day P.O., withdraw concomitant AED by 20% decrements each week over 4-week period.

➣ Conversion from adjunctive therapy with valproate to monotherapy with lamotrigine for seizures

Adults and children ages 16 and older: Achieve lamotrigine dosage of 200 mg/day P.O. and maintain previous stable valproate dosage. Maintain lamotrigine dosage of 200 mg/day and decrease valproate dosage to 500 mg/day by decrements no greater than 500 mg/day; maintain regimen for 1 week. Then increase lamotrigine dosage 300 mg/day while simultaneously decreasing valproate to 250 mg/day; maintain regimen for 1 week. Then discontinue valproate completely and increase lamotrigine dosage by 100 mg/day every week to 500 mg/day.

➣ Maintenance treatment of bipolar I disorder to delay time to occurrence of mood episodes in patients treated with standard therapy for acute mood episodes

Adults: Target dosage is 200 mg P.O. daily titrated over 7 weeks (or 100 mg daily in patients taking valproate, or 400 mg daily in patients not taking valproate who are receiving carbamazepine, rifampin, phenytoin, phenobarbital, or primidone). If other psychotropic drugs are withdrawn following stabilization, adjust lamotrigine dosage as indicated.

Dosage adjustment

• Moderate to severe hepatic dysfunction
• Renal impairment
• Heart disease
• Starting or stopping estrogen-containing oral hormonal contraceptives
• Concurrent use of valproate

Off-label uses

• Drug-resistant seizures
• Mood stabilization in rapid-cycling bipolar II disorder

Contraindications

• Hypersensitivity to drug or its components

Precautions

Use cautiously in:
• renal or hepatic impairment or other diseases or conditions that affect metabolism or elimination
• concurrent use of other anticonvulsants or estrogen-containing oral contraceptives
• history of allergy to or rash from other AEDs
• pregnant or breastfeeding patients
• children younger than age 2 children younger than age 18 with mood disorders (safety and efficacy).

Administration

• Give with or without food.
• Don't crush or break regular tablets; make sure patient swallows them whole.
• Crush chewable tablets or mix in diluted fruit juice if patient can't chew them.
• Be aware that effectiveness of drug in treating acute mood episodes hasn't been established.
☞ Be aware that abrupt drug withdrawal may induce seizures. If drug must be discontinued, decrease dosage by 50% per week over at least 2 weeks.
☞ Don't confuse Lamictal with other drugs having sound-alike names (such as Lamisil, Lomotil, and Ludiomil).

Route	Onset	Peak	Duration
P.O.	Unknown	1.4-4.8 hr	Unknown

Adverse reactions

CNS: dizziness, vertigo, headache, drowsiness, ataxia, incoordination, insomnia, sleep disorders, tremor, depression, anxiety, irritability, impaired memory, poor concentration, emotional lability, racing thoughts, dysarthria, malaise, asthenia, somnolence, amnesia, hypoesthesia, decreased or increased reflexes, fatigue, migraine, dream abnormality, suicidal ideation, seizures

CV: palpitations, hemorrhage

EENT: diplopia, nystagmus, blurred vision, possible long-term ophthalmologic effects, ear disorder, rhinitis, epistaxis, sinusitis, pharyngitis

GI: nausea, vomiting, diarrhea, constipation, abdominal pain, dyspepsia, dry mouth, anorexia, peptic ulcer, flatulence, rectal hemorrhage

GU: dysmenorrhea, amenorrhea, vaginitis, increased libido, urinary tract infection, urinary frequency, penis disorder

Musculoskeletal: muscle spasm, neck pain, back pain, arthralgia, myalgia

Respiratory: cough, dyspnea, bronchitis, bronchospasm

Skin: pruritus, contact dermatitis, dry skin, sweating, photosensitivity, eczema, alopecia, rash, urticaria, erythema multiforme, toxic epidermal necrolysis, Stevens-Johnson syndrome

Other: infection, pain, weight changes, chest pain, accidental injury, lymphadenopathy, flulike syndrome, fever, tooth disorder, edema, peripheral edema, facial edema, hypersensitivity reactions (rare) including anaphylaxis

Interactions

Drug-drug. Carbamazepine, phenobarbital, phenytoin, primidone: decreased lamotrigine steady-state level

Estrogen-containing oral contraceptives, rifampin: increased lamotrigine clearance

Folate inhibitors (such as methotrexate, co-trimoxazole): additive effects of lamotrigine

Topiramate: increased topiramate concentrations

Valproate: decreased lamotrigine clearance, increased steady-state level

Drug-diagnostic tests. Liver function tests: abnormal

Drug-behaviors. Sun exposure: photosensitivity

Patient monitoring

☞ Watch for signs and symptoms of hypersensitivity reaction (Stevens-Johnson syndrome or anaphylaxis).
☞ Monitor patient with bipolar disorder closely for clinical worsening and suicidality.
• Monitor vital signs regularly.
• Monitor CNS status carefully, noting adverse reactions and changes in seizure pattern.
• Monitor lamotrigine blood levels, especially during dosage adjustments.

Patient teaching

• Tell patient or caregiver that drug may be taken with or without food.
• Instruct patient or caregiver that regular tablets must be swallowed whole without crushing or breaking.
• Instruct patient or caregiver to crush chewable tablets or mix them in diluted fruit juice if patient can't chew them. Tell patient to add dispersed tablets to approximately 1 teaspoon of liquid in glass or spoon, mix solution when tablets are completely dispersed, and then take entire amount immediately.
• Inform patient or caregiver that dosage is adjusted slowly, as indicated.
☞ Advise patient or caregiver to stop drug and notify prescriber immediately at first sign of rash.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.