Page 24 - FPGEE Medicinal and Organic Chemistry Q&A Book

Krisman

concentration of cisplatin is very low due to the 264. (d) Busulfan (Myleran) is a chemotherapy
fact that the drug is highly bound to plasma pro- drug that is a cell cycle non-specific alkylating
tein, and therefore reaction of sodium thiosulfate agent (slows the growth of cancer cells). More
with cisplatin in blood is very slow and low (Fig: specifically it belongs to a subclass of alkylat-
11.14, page 149). ing agents known as alkyl sulfonates. The
IUPAC name for this compound is 1,4-
261. (c) The water-soluble non-toxic product bis(methylsulfonyloxy)butane. It is indicated for
of the reaction is CHOCH CH SCH CH SO - the treatment of chronic myelogenous leukemia.
2 2 2 2 3
(Fig: 11.15, page 149). Serious bone marrow suppression including
pancytopenia is a major side effect of the drug.
Recovery from busulfan-induced pancytopenia
262. (c) N,N’N’ triethylenethiophosphoramide,
can take up to 2 years.
abbreviated “ThioTEPA,” is an organophospho-
rus compound. It is mostly used to treat breast
265. (c) Doxorubicin (Adriamycin) is classified
cancer, ovarian cancer, and bladder cancer. It is
as an anthracycline antineoplastic antibiotic. It
also used as conditioning for bone marrow
is structurally very similar to tetracycline anti-
transplantation. Its main toxicity is
biotics. Structurally, it is a glycoside and
myelosuppression. Triethylenephosphoramide
contains a sugar portion (L-daunosamine) and
(TEPA) is the active metabolite of the drug.
a nonsugar portion. The nonsugar portion of
glycoside is generally known as an aglycone.
CH 2 S CH 2 In anthracyclines, the aglycone moiety is spe-
N P N cifically called anthracyclinone or an-
CH 2 N CH 2 thraquinone.

CH CH 266. (b) Severe cardiac toxicity is reported with
2 2
use of anthracyclene antineoplastic antibiotics
Thiotepa
such as daunorubicin (Cerubidine) and doxo-
rubicin (Adriamycin). The formation of
CH O CH
2 2 cytotoxic free radicals by anthracyclins is
N P N responsible for this. A free radical is normally
defined as a highly reactive species with an
CH CH
2 2
N unpaired electron. When NADPH reductase
reduces anthracycline antibiotics, it releases su-
CH CH
2 2 -)
peroxide radical anion (.O2 . This anion, with
Triethylenephosphoramide the help of enzyme superoxide dismutase,
(active metabolite of Thiotepa) converts into hydrogen peroxide (H O ). In the
2 2
presence of the enzyme catalase, this H O is
2 2
readily converted into water and oxygen, which
263. (c) Carmustine or BiCNU (Bis-
are harmless and non toxic for the body. How-
ChloroNitrosoUrea) is classified in the
+2
ever in the presence of the ferrous (Fe ) ion,
nitrosourea class of chemotherapy agents. It is
hydrogen peroxide is converted into a highly
highly lipophilic and indicated for the treatment
toxic free hydroxyl radical through the process
of brain tumors and Hodgkin’s disease.
called Fenton reaction. When these cytotoxic
Thrombocytopenia, leukopenia and severe pul-
free radicals are generated within the heart, it
monary toxicity (dose-related only) are reported
may cause severe damage to cardiac tissues
side effects of the drug.
since cardiac tissues do not contain enzyme cata-
lase (fig:11.16, page 149).
www.pharmacyexam.com 148