If it's Phenergan, it doesn't come in .25 mg size, or 5 mg, but there is a 25 mg size, and a 12.5mg. If the name of the drug is wrong, the size might be read wrong also. If it's really 25mg vs 12.5mg, then 25 mg is twice as much as 12.5mg. If you're not sure you are reading it right, you can call ...