Analysis of Illicit Drugs in Human Biological Samples by LC-MS n - LC-MS in Drug Bioanalysis - page 362

glucuronic conjugates: the 4-phenyl-4-piperidine cyclohexanol and 1-(1-phenyl
cyclohexyl)-4-hydroxy-piperidine (PCHP). About 30 % of the dose is excreted in
the urine in 10 days: 16 % of this can be traced as a molecule as it is, while 30 % is
in the form of conjugated hydroxy metabolite. The amount of substance, as it is,
increases in acidic condition. The remaining dose is excreted in the feces [ 24 ] .

5.2.2 Ketamine

Ketamine, 2-chlorophenyl-2-(methylamino)cyclohexan-1-one, a general anesthetic,
is used for its ability to induce amnesia and loss of response to painful stimuli with-
out loss of consciousness [ 25 ]. It has been used since 1967, but to date is still used
only in veterinary. Even if taken in subanesthetic doses, psychotropic and hallucino-
genic effects occur, so since the 1980s the drug has begun to be consumed in the
world of clubs. Ketamine is produced as an injectable solution, but after evaporation
remains a powder that can be used, as for other drugs of abuse, to produce tablets or
to be sniffed. Some street names are used for identification: K , Special K , Vitamin
K , Superacid , Ket , Kit-Kat , Kitty . The chemical structure, mechanism of action, and
pharmacological effects are similar to those of PCP, although ketamine is less potent
and produces only minor side effects; moreover, duration of the effect is reduced
compared to the PCP.

Pharmacodynamics

Ketamine can be taken by intravenous, intramuscular, nasal or oral means and some-
times it can be smoked with tobacco. With nasal intake, plasmatic peak concentration
is reached after about an hour, but results can be seen earlier within approximately
20 min if the intake is intramuscular [ 25 ]. Due to its high lipophilicity, ketamine is
rapidly distributed in the brain and is then distributed to less vascularized organs and
adipose tissue, where its accumulation is possible. Ketamine is also responsible for
the increased adrenergic tone and cardiovascular symptoms activating [ 26 ] .

Pharmacokinetics

Ketamine is metabolized primarily in the liver region leading to the formation of
two main compounds: norketamine (NK) and dehydronorketamine (DHNK). NK, a
compound much less powerful than the substance itself, is achieved through the
demethylation, subsequent dehydrogenation generates DHNK [ 27, 28 ] .
Both the ketamine as it is and the metabolites are hydroxylated and conjugated
before elimination. About 90 % of the dose is excreted in the urine within 72 h, with
about 2 % as it is, 2 % as NK, 16 % as DHNK, and 80 % as conjugates of hydroxy-
lated metabolites [ 29 ] .