Available in 100 mg and 300 mg capsules. Free shipping on orders over $49 and 100% Satisfaction Guaranteed from America's Largest Pet PharmacyGabapentin is available as 100 mg, 300 mg, and 400 mg capsules. The usual dose to treat seizures in dogs is 4.5 to 13.5 mg per lb every 8 to 12 hours....