SPL Set ID: 3e2c9a35-6a39-41d7-ad84-3c0bb8894b09

LAMICTAL XR (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: LAMICTAL XR extended-release tablets are supplied for oral administration as 25-mg (yellow with white center), 50-mg (green with white center), 100-mg (orange with white center), 200-mg (blue with white center), 250-mg (purple with white center), and 300-mg (gray with white center) tablets. Each tablet contains the labeled amount of lamotrigine and the following inactive ingredients: glycerol monostearate, hypromellose, lactose monohydrate; magnesium stearate; methacrylic acid copolymer dispersion, polyethylene glycol 400, polysorbate 80, silicon dioxide (25- and 50-mg tablets only), titanium dioxide, triethyl citrate, carmine (250-mg tablet only), iron oxide black (50-, 250-, and 300-mg tablets only), iron oxide yellow (25-, 50-, and 100-mg tablets only), iron oxide red (100-mg tablet only), FD&C Blue No. 2 Aluminum Lake (200- and 250-mg tablets only). Tablets are printed with edible black ink. LAMICTAL XR extended-release tablets contain a modified-release eroding formulation as the core. The tablets are coated with a clear enteric coat and have an aperture drilled through the coats on both faces of the tablet (DiffCORE) 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. Lamictal XR Chemical Structure