SPL Set ID: e45bd69f-3580-ff15-e053-2a95a90a4615

Lamotrigine, 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 C 9 H 7 N 5 Cl 2 , and its molecular weight is 256.09. Lamotrigine is a white to pale cream-colored powder and has a pK a 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: Lamotrigine Extended-Release Tablets, USP are supplied for oral administration as 25-mg (yellow), 50-mg (green), 100-mg (orange), 200-mg (blue), 250-mg (purple), and 300-mg (gray) tablets. Each tablet contains the labeled amount of lamotrigine and the following inactive ingredients: hypromellose, lactose monohydrate, magnesium stearate, methacrylic acid and ethyl arcylate copolymer dispersion, mono- and di-glycerides, polysorbate 80, silicon dioxide(25- and 50- mg tablets only), sodium hydroxide, sodium lauryl sulfate, titanium dioxide, triethyl citrate, iron oxide black(50- and 300- mg tablets only), iron oxide red(100- and 250- mg tablets only), iron oxide yellow(25-, 50-, 100- mg tablets only), FD&C Blue No. 2 Aluminum Lake(200- and 250- mg tablets only). Tablets are printed with edible black ink (black ink is composed of ferrosoferric oxide, propylene glycol and shellac). Lamotrigine Extended-Release Tablets, USP contain a modified-release formulation as the core. The tablets are coated with a clear enteric coat to enable a controlled release of drug in the acidic environment of the stomach. The combination of this and the modified-release core are designed to control the dissolution rate of lamotrigine over a period of approximately 12 to 15 hours, leading to a gradual increase in serum lamotrigine levels. FDA approved dissolution test specifications differ from USP. Chemical Structure