Clioquinol and iodoquinol are found in topical compounds for dermatologic use. Their application in pediatrics has been for treatment of diaper dermatitis, although the current labeling for these products advises against their use in children younger than 2 years of age. The Table lists a few of the many agents currently available that contain clioquinol or iodoquinol. Some nonprescription products also contain clioquinol.
Since our 1974 commentary on the toxicity of these drugs to children,1 additional reports of toxicity following skin application have become available. Both clioquinol and iodoquinol have been known to cause serious and irreversible optic atrophy and peripheral neuropathy.2 This class of drugs was associated with several thousand cases of subacute myelo-optic neuropathy in Japan.3-5 The clinical picture was that of a subacute onset of peripheral weakness and sensory loss, spastic paraparesis, and blindness, occurring in combination in various degrees. The most common symptoms were muscular weakness of the lower extremities and dysesthesia spreading to the trunk.
A World Health Organization committee convened in 1977 to prepare a list of essential drugs and excluded clioquinol because it considered the risks of treatment greater than the potential benefit.6 Other authoritative sources of drug information state that "clioquinol has limited topical antibacterial and antifungal activity"7 and that "routine use of either compound (clioquinol or iodoquinol) is not recommended."8
A recent clinical study examined the percutaneous absorption of clioquinol.9 Five healthy male subjects received one application (5 g) of 3% clioquinol cream applied for 12 hours to a 200 cm2 area of the forearm (1.1% of body surface area).