Monograph: |
Di-iodohydroxyquinoline
A light yellowish to tan-coloured, microcrystalline powder,
not readily wetted in water, odourless or with a slight odour.
Practically insoluble in water: sparingly soluble in alcohol
and ether.
Adverse Effects
Major concerns have been expressed about the safely of the
halogenated hydroxyquinolines since the recognition of se-
vere neurotoxicity with clioquinol. In Japan, the epidemic de-
velopment of subacute myelo-opticoneuropathy (SMON) in
the 1960s was associated with the ingestion of normal or high
doses of clioquinol for prolonged periods and the sale of clio-
quinol and related hydroxyquinolines was subsequently
banned in Japan. Symptoms of subacute myelo-opticoneu-
ropathy are principally those of peripheral neuropathy, in-
cluding optic atrophy, and myelopathy. Abdominal pain and
diarrhoea often precede neurological symptoms such as par-
aesthesias in the legs progressing to paraplegia in some pa-
tients and loss of visual acuity sometimes leading to
blindness. Cerebral disturbances, including confusion and
retrograde amnesia, have also been reported. Although many
patients improved when clioquinol was withdrawn, others
had residual disablement.
It was suggested that the Japanese epidemic might have been
due to genetic susceptibility, but a few similar cases of suba-
cute myelo-opticoneuropathy have been reported from sever-
al other countries in association with clioquinol or related
hydroxyquinoline derivatives, such as broxyquinoline or di-
iodohydroxvquinoline.
Di-iodohydroxyquinoline has also been associated with gas-
tro-intestinal effects such as abdominal cramps, nausea, and
diarrhoea. Adverse effects which may be attributable to the
iodine content of di-iodohydroxyquinoline include pruritus
ani, skin eruptions, and enlargement of the thyroid gland. Fe-
ver, chills, headache, and vertigo have also occurred.
Precautions
Di-iodohydroxyquinoline is contra-indicated in patients
known to be hypersensitive to iodine or halogenated hydrox
yquinolines and io those with impaired kidney or liver func
tion. It should be used with caution in thyroid disease ant
may interfere with determinations of protein-bound iodine foi
up to 6 months in tests lor thyroid function. Its use is best
avoided in patients with neurological disorders. Long-term
use should be avoided.
The Committee on Drugs of the American Academy of
Pediatrics considered that there was a potential risk of toxic-
ity to infants and children from clioquinol and di-iodohydrox-
yquinoline applied topically. Since alternative effective
preparations are available for dermatitis the Committee rec-
ommended that products containing either of these com-
pounds should not be used.
Also the WHO considered that the use of halogenated hy-
droxyquinolines for the treatment of acute diarrhoea or arnoe-
biasis in children cannot be justified.2 There is no evidence of
their efficacy in acute diarrhoea and they have been associated
with severe neurological effects. On the rare occasions when
a luminal amoebicide is required other less toxic and more
effective agents are available.
Pharmacokinetics
Di-iodohydroxyquinoline is partly and irregularly absorbed
from the gastro-intestinal tract. Concern has been expressed
about possible absorption following application to the skin
(see above).
Uses and Administration
Di-iodohydroxyquinoline, a halogenated hydroxyquinoline,
is a luminal amoebicide acting principally in the bowel lumen
and is used in the treatment of intestinal amoebiasis. although
a less toxic amoebicide such as diloxanide furoate is usually
preferred: children should not be treated with di-iodohydrox-
yquinoline (see Precautions, above). It is given alone in the
treatment of asymptomatic cyst-passers and in conjunction
with an amoebicide that acts in the tissues, such as metroni-
dazole, in patients with invasive amoebiasis. The usu-
al dosage in the treatment of amoebiasis is 630 or 650 mg
three times daily by mouth for 20 days.
Di-iodohydroxyquinoline has also been given in the treatment
Of Dientamoeba fragilis infections, in balantidiasis as
an alternative to tetracycline, and in Blastocystis hominis in-
fections.
Di-iodohydroxyquinoline was formerly used in the treatment
of acrodermatitis enteropathica; it is reported to act by en-
hancing zinc absorption and has now been superseded by oral
zinc therapy.
Di-iodohydroxyquinoline is claimed to have some antibacte-
rial and antifungal activity and has been used topically (but
see under Precautions, above).
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