Toluene abusers generally employ one of two methods
to achieve a ‘‘high’’ with this substance: ‘‘huffing,’’
in which a rag is soaked with toluene and the
fumes are directly inhaled, and ‘‘bagging,’’ in which
the fumes are inhaled as they arise from the solvent
placed in a plastic bag. After inhalation, toluene is rapidly
absorbed through the lungs and then widely distributed
throughout the body (8). Most inhaled toluene
is metabolized in the liver by conversion to benzoic
acid by two enzymes, alcohol dehydrogenase and aldehyde
dehydrogenase (6). Benzoic acid is then conjugated
with glycine to form hippuric acid (80%) or
glucuronic acid to form benzoylglucuronide (20%),
both of which are water soluble and readily eliminated
through the kidneys (8). Hippuric acid is the major metabolite
of toluene, and up to 75% of inhaled toluene
is excreted in the urine as hippuric acid within 12 hours
after exposure (9). Toluene is retained somewhat longer
in adipose tissue, where its half-life is 0.5 to 3 days
(9). The highly lipophilic nature of toluene explains its rapid concentration in the lipid-rich central nervous system (CNS; 1).