Elephant Formulary

© 2003-17 Susan K. Mikota DVM and Donald C. Plumb, Pharm.D. Published by
Elephant Care International

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Elephant specific information, if available, is in blue.

Chemistry – Also known as iodochlorhydroxyquin , clioquinol possesses antibacterial, antifungal and amoebicidal activity. It occurs as a tasteless, voluminous, yellowish white to brownish yellow powder that has a slight characteristic odor. The drug is practically insoluble in water and al­cohol.


Storage/Stability/Compatibility – Unless otherwise directed, store clioquinol boluses at room temperature and protect from light.


Pharmacology – Information on the mechanism of action of clioquinol was not located, but its action is probably due to its iodine content. It is reportedly active against some cocci, E. coli, yeasts, and some protozoal parasites, particularly Trichomonas sp..


Uses/Indications – Clioquinol boluses are approved for oral use in horses to treat diarrheas that have failed to respond to regular forms of treatment, particularly if caused by some protozoal organisms. Clioquinol was once used orally in humans to treat diarrhea, but severe neurotoxic reactions have eliminated its use in humans, except as a topical antifungal.


Pharmacokinetics – The drug is only minimally absorbed after oral administration in horses. No other information was noted.


Contraindications/Precautions/Reproductive Safety – Not to be used in horses intended for food. No other information located.


Adverse Effects/Warnings – The manufacturer does not list any adverse effects for this product when used orally in horses. In humans, subacute myelo-opticoneuropathy was seen in many patients taking the drug orally for prolonged periods of time. It is unknown if the drug causes neurotoxic effects in horses. Topical administration for 28 days of the 3% topical preparation has caused toxicity in dogs.


Overdosage/Acute Toxicity – No specific information located regarding overdosage in horses. Iodism or potentially neurotoxic reactions (see Adverse effects above) could result.


Drug InteractionsDrug/Laboratory Interactions – None located, but the iodine component of the drug may affect some thyroid function tests.


Doses –


For chronic diarrhea in horses:

a)   1 bolus (10 g) for a 1000 lb horse PO daily until feces become formed. Then reduce dose and give daily or reduce dose and give on alternate days or even less frequently. (Package insert; Rheaform® Boluses—Solvay)


Monitoring Parameters –

1)   Clinical efficacy

2)   Occasional neurological evaluations recommended with prolonged therapy



Dosage Forms/Preparations/FDA Approval Status/Withholding Times –


Veterinary-Approved Products: Note: Current marketing status is unknown.

Clioquinol Oral Boluses 10 g; Rheaform® Boluses  (Fort Dodge); (Rx)  Approved for use in horses.


   Human-Approved Products: No systemic products approved in the United States. Topical formulations are available.