What it metabolizes into isn't very important. GHB is quite dangerous when used alongside other respiratory depressants, most commonly alcohol. They have a synergistic effect on respiratory depression.
What a drug is metabolised into is sometimes how it treats a patient. Grapefruit can slow down some of the P450 enzymes so drugs like heart condition drugs can kill, and Viagra in combination with grapefruit will give you a priaprism that lasts for hours. 2 Litres of grapefruit juice + 50mg of Viagra to be exact is all you need, and to go down, you need a visit to the A&E dept who will inject both sides of your penis with andrenaline, or getting a couple of epipens from the darkweb could also save you a trip to the A&E dept if you want to do it yourself.
Tobacco speeds up the metabolise of some drugs again altering some of the P450 enzymes, like caffeine so instead of it lasting in the body for about 8hrs, its cleared in 4hrs, yet some other prescription drugs including some female contraceptives can make caffeine last in the body for over a day, which explains why some people are sensitive to it. Viagra and poppers is also a big no no as it can cause a fatal drop in blood pressure, but so can ingesting large quantities of potassium. Paracetamol also slows down some P450 enzymes so when combined with alcohol, the alcohol can reach toxic levels in the body and kill. Its an easy suicide method if you know the right amounts to take.
To bypass the liver which is like a safety net for the body, inhale drugs like cocaine, hold them under your tongue as the skin is thin there or stick them up your bum which also has thin skin and thus easily absorbed.
Pretty much anything is dangerous at the wrong dose, the wrong delivery method and those Lethal Doses can be affected by other foods and drugs which many people may not think anything of, so just be careful.
It's also pretty habit-forming.