Sodium and potassium iodide have both been administered to treat selected bacterial, actinomycete, and fungal infections, although sodium iodide is preferred. The in vivo effects of iodides against fungal cells are not well understood. Iodide is readily absorbed from the GI tract and distributes freely into the extracellular fluid and glandular secretions. Iodide concentrates in the thyroid gland (to a level 50 times greater than plasma levels) and to a much lesser degree in salivary, lacrimal, and tracheobronchial glands. Long-term use at high levels leads to accumulation in the body and to iodinism.
Clinical signs of iodinism include lacrimation, salivation, increased respiratory secretions, coughing, inappetence, dry scaly skin, and tachycardia. Cardiomyopathy has been reported in cats. Host defense systems, such as decreased immunoglobulin production and decreased phagocytic ability of leukocytes, are also impaired. Iodinism may also lead to abortion and infertility.
Sodium iodide has been administered successfully to treat cutaneous and cutaneous/lymphadenitis forms of sporotrichosis; attempts to control various other mycotic infections with iodides yield equivocal results.
The dosage for sodium iodide (20% solution) is 44 mg/kg/day, PO, for dogs, and 22 mg/kg/day, PO, for cats. The dosage for horses is 125 mL of 20% sodium iodide solution, IV, daily for 3 days, then 30 g, PO, daily for 30 days after clinical remission. The dosage for treating actinomycosis and actinobacillosis in cattle is 66 mg/kg, by slow IV, repeated weekly. Potassium iodide should never be injected intravenously.