Widmark's formula helps in the measurement of the blood level of -
The basis for calculating the approximate quantity of alcohol in the body, after equilibrium between the blood and the tissues has been reached, is expressed by the Widmark's formula

a = p.r.c.
a-Weight of alcohol in g in body
p- the weight of the body in kg
c- concentration of alcohol in blood in g/kg
r- a constant obtained by dividing the average concentration of alcohol in the body by the average concentration of
alcohol in the blood (0.085 for men, 0.055 for women)

For urine, formula is- a=3/4 p.r.q., where q - concentration of alcohol in urine in mg/kg
Cocaine
Alcohol
Barbiturates
Benzodiazepines