What is the difference between methadone and methamphetamine?

Just about everything is, other than the first four letters. They are completely different drugs and have completely different affects.

Methadone is a synthetic opiod analgesic (pain killer/ reliever) prescribed to patients to treat severe chronic pain. Methadone is long-acting and usually does not cause "euphoria" as other opiods do, such as morphine and oxycodone. It's also, and mostly used, to treat opiate addiction of those "hooked" on heroin, morphine, etc., and it's mainly used as a managed treatment for drug addiction to prevent withdrawals, etc.

Methamphetamine is a central nervous system stimulant, rarely used in the medical field, but illegally made in "meth labs" to sell on the street to those wanting a cheap 'speed-like' high. It is very addictive and can cause negative personality changes, brain damage, and deterioration of physical appearance, such as rotting and/or missing teeth, acne, paranoia, weight loss.