Biomedical Engineering Reference
In-Depth Information
3.3.2
Pharmacokinetics
After intravenous administration heroin is very quickly metabolized (half-life is
about 3 min) into 6-MAM and morphine. The 6-MAM reaches its maximum con-
centration in 6 min, then transforms itself into morphine, which reaches its peak in
20 min. In the liver and kidneys, deacetylation occurs, but in the liver other reactions
also occur: N-demethylation that leads to normorphine, methylation that leads to
codeine and conjugation with glucuronic acid.
The formation of glucuronide metabolites is the major catabolic route of mor-
phine; in fact it is excreted at 85-90 % in the form of morphine 3-glucuronide
(M3G) [
10
] .
4
Psychostimulants
4.1
Cocaine
Cocaine is an alkaloid contained in great amounts in coca leaves and
Erythroxylon
coca
and
Erythroxylon novogranatense
.
Erythroxylon coca
is a native shrub of Peru
and Bolivia and is now widely cultivated in Central and South America and parts of
Asia. The leaves of these plants contain between 0.4 and 2.5 % of alkaloids of which
50-60 % is represented by cocaine. This is a benzyl and methyl ester of ecgonine
and is the active ingredient, which determines the psychotropic effects. It was iso-
lated for the first time by the German chemist F. Gaedcke and was later character-
ized in 1860 by F. Wohler (Fig.
2
); only the
l
form is pharmacologically active.
It is a white crystalline solid, slightly soluble in water, but soluble in acidic aque-
ous solutions and soluble in organic solvents, such as chloroform and diethyl ether.
It is available in the illicit market as hydrochloride salt or free base (crack). Cocaine
is usually mixed with other substances used as excipients.
H
3
C
O
N
CH
3
O
O
O
Fig. 2
Structure of cocaine
