A large number of benzodiazepines are available. There are major differences in potency between different benzodiazepines, so that equivalent doses vary as much as 20-fold. For example, 0.5 milligrams (mg) of alprazolam (Xanax) is approximately equivalent to 10mg of diazepam (Valium). Thus a person on 6mg of alprazolam daily, a dose not uncommonly prescribed in the US, is taking the equivalent of about 120mg of diazepam, a very high dose. These differences in strength have not always been fully appreciated by doctors, and some would not agree with the equivalents given here. Nevertheless, people on potent benzodiazepines such as alprazolam, lorazepam (Ativan) or clonazepam (Klonopin) tend to be using relatively large doses. This difference in potency is important when switching from one benzodiazepine to another, for example changing to diazepam during withdrawal, as described in the next chapter.