Combinations - drug dosages depend on what ?

[Ximot]

body weight?
--a factor for some drugs like ketamine or alcohol, for instance, but not others, e.g. not for paracetamol it seems

tolerance?
--depends on the drug a lot.

sex?
--m/f/... (to do with body fat and metabolism and...?!)

individual differences in sensitivity
-- (due to enzymes or whatever?)

food intake prior, obviously...

I especially welcome people's experiences on which drugs' dosages are affected by body weight and which ones aren't. Particularly keen here on RCs, but any info welcomed.

peace
ximot