Lamotrigine Extended Release (Page 7 of 11)

8.2 Lactation

Risk Summary

Lamotrigine is present in milk from lactating women taking lamotrigine extended-release (see Data). Neonates and young infants are at risk for high serum levels because maternal serum and milk levels can rise to high levels postpartum if lamotrigine dosage has been increased during pregnancy but is not reduced after delivery to the pre-pregnancy dosage. Glucuronidation is required for drug clearance. Glucuronidation capacity is immature in the infant and this may also contribute to the level of lamotrigine exposure. Events including rash, apnea, drowsiness, poor sucking, and poor weight gain (requiring hospitalization in some cases) have been reported in infants who have been human milk-fed by mothers using lamotrigine; whether or not these events were caused by lamotrigine is unknown. No data are available on the effects of the drug on milk production.

The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for lamotrigine extended-release and any potential adverse effects on the breastfed infant from lamotrigine extended-release or from the underlying maternal condition.

Clinical Considerations

Human milk-fed infants should be closely monitored for adverse events resulting from lamotrigine. Measurement of infant serum levels should be performed to rule out toxicity if concerns arise. Human milk-feeding should be discontinued in infants with lamotrigine toxicity.

Data

Data from multiple small studies indicate that lamotrigine plasma levels in nursing infants have been reported to be as high as 50% of maternal plasma concentrations.

8.4 Pediatric Use

Lamotrigine extended-release is indicated as adjunctive therapy for PGTC and partial-onset seizures with or without secondary generalization in patients aged 13 years and older. Safety and effectiveness of lamotrigine extended-release for any use in patients younger than 13 years have not been established.

Immediate-release lamotrigine is indicated for adjunctive therapy in patients aged 2 years and older for partial-onset seizures, the generalized seizures of Lennox-Gastaut syndrome, and PGTC seizures.

Safety and efficacy of the immediate-release lamotrigine, used as adjunctive treatment for partial-onset seizures, were not demonstrated in a small, randomized, double-blind, placebo-controlled, withdrawal trial in very young pediatric patients (aged 1 to 24 months). Immediate-release lamotrigine was associated with an increased risk for infectious adverse reactions (lamotrigine 37%, placebo 5%), and respiratory adverse reactions (lamotrigine 26%, placebo 5%). Infectious adverse reactions included: bronchiolitis, bronchitis, ear infection, eye infection, otitis externa, pharyngitis, urinary tract infection, and viral infection. Respiratory adverse reactions included nasal congestion, cough, and apnea.

Juvenille Animal Data

In a juvenile animal study in which lamotrigine (oral doses of 0, 5, 15, or 30 mg/kg) was administered to young rats from postnatal day 7 to 62, decreased viability and growth were seen at the highest dose tested and long-term behavioral abnormalities (decreased locomotor activity, increased reactivity, and learning deficits in animals tested as adults) were observed at the two highest doses. The no-effect dose for adverse developmental effects in juvenile animals is less than the human dose of 400 mg/day on a mg/m2 basis.

8.5 Geriatric Use

Clinical trials of lamotrigine extended-release for epilepsy did not include sufficient numbers of patients aged 65 years and older to determine whether they respond differently from younger patients or exhibit a different safety profile than that of younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

8.6 Hepatic Impairment

Experience in patients with hepatic impairment is limited. Based on a clinical pharmacology study with the immediate-release lamotrigine in 24 subjects with mild, moderate, and severe liver impairment [see Clinical Pharmacology (12.3)] , the following general recommendations can be made. No dosage adjustment is needed in patients with mild liver impairment. Initial, escalation, and maintenance doses should generally be reduced by approximately 25% in patients with moderate and severe liver impairment without ascites and 50% in patients with severe liver impairment with ascites. Escalation and maintenance doses may be adjusted according to clinical response [see Dosage and Administration (2.1)].

8.7 Renal Impairment

Lamotrigine is metabolized mainly by glucuronic acid conjugation, with the majority of the metabolites being recovered in the urine. In a small study comparing a single dose of immediate-release lamotrigine in subjects with varying degrees of renal impairment with healthy volunteers, the plasma half-life of lamotrigine was approximately twice as long in the subjects with chronic renal impairment [see Clinical Pharmacology (12.3)].

Initial doses of lamotrigine extended-release should be based on patients’ AED regimens; reduced maintenance doses may be effective for patients with significant renal impairment. Few patients with severe renal impairment have been evaluated during chronic treatment with lamotrigine. Because there is inadequate experience in this population, lamotrigine extended-release should be used with caution in these patients [see Dosage and Administration (2.1)].

10 OVERDOSAGE

10.1 Human Overdose Experience

Overdoses involving quantities up to 15 g have been reported for immediate-release lamotrigine, some of which have been fatal. Overdose has resulted in ataxia, nystagmus, seizures (including tonic-clonic seizures), decreased level of consciousness, coma, and intraventricular conduction delay.

10.2 Management of Overdose

There are no specific antidotes for lamotrigine. Following a suspected overdose, hospitalization of the patient is advised. General supportive care is indicated, including frequent monitoring of vital signs and close observation of the patient. If indicated, emesis should be induced; usual precautions should be taken to protect the airway. It is uncertain whether hemodialysis is an effective means of removing lamotrigine from the blood. In 6 renal failure patients, about 20% of the amount of lamotrigine in the body was removed by hemodialysis during a 4-hour session. A Poison Control Center should be contacted for information on the management of overdosage of lamotrigine extended-release.

11 DESCRIPTION

Lamotrigine extended-release, an AED of the phenyltriazine class, is chemically unrelated to existing AEDs. Lamotrigine’s chemical name is 3,5-diamino-6-(2,3-dichlorophenyl)-as -triazine, its molecular formula is C9 H7 N5 Cl2 , and its molecular weight is 256.09. Lamotrigine is a white to pale cream-colored powder and has a pKa of 5.7. Lamotrigine is very slightly soluble in water (0.17 mg/mL at 25°C) and slightly soluble in 0.1 M HCl (4.1 mg/mL at 25°C). The structural formula is:

Chemical structure
(click image for full-size original)

Lamotrigine Extended-Release Tablets are supplied for oral administration as 25 mg (round beige biconvex film-coated), 50 mg (round white biconvex film-coated), 100 mg (round brown biconvex film-coated), 200 mg (round yellow biconvex film-coated), 250 mg (round white biconvex film coated) and 300 mg (round grey biconvex film-coated) tablets. Each tablet contains the labeled amount of lamotrigine and the following inactive ingredients: hypromellose, lactose monohydrate, magnesium stearate, colloidal anhydrous silica (25 mg, 50 mg, 200 mg, 250 mg and 300 mg tablets only), methacrylic acid copolymer, talc, titanium dioxide, triethyl citrate, sodium bicarbonate, sodium laurel sulfate, iron oxide yellow (25 mg and 100 mg tablets only), iron oxide red (25 mg and 100 mg tablets only), D&C Yellow # 10 (200 mg tablet only), FD&C Yellow # 6 (200 mg tablet only) and black iron oxide (300 mg tablet only).

Lamotrigine extended-release tablets contain a modified-release eroding formulation as the core. The tablets are coated with an enteric coat and have pore forming ingredient in the coat to enable a controlled release of the drug in the acidic environment of the stomach. The combinations of the modified-release core and the enteric coat are designed to control the dissolution rate of lamotrigine over a period of approximately 12 to 15 hours, leading to a gradual increase in blood lamotrigine levels.

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