When a patent for a brand name drug expires, pharmaceutical company can make a generic form of the drug. Effexor patent expired in 2006, since then several
generics are available. Those
generics are usually cheaper but they must contain the same active ingredient(s), the same dosage form, at the same dose or concentration, and for the same route of administration. The generics are usually cheaper and can use different inactive ingredients and preservatives which can sometimes cause trouble.