potassium iodide
Brand: SSKI, ThyroShield, Iosat
Drug Class: antithyroid agent / iodine supplement
Drug Family: antithyroid
Subclass: inorganic iodide preparation
Organ Systems: endocrine
Mechanism of Action
Large doses of iodine suppress thyroid hormone synthesis and release via the Wolff-Chaikoff effect (transient inhibition of iodide organification and hormone synthesis) and reduce thyroid vascularity. Paradoxically inhibits hormone release from the hyperactive thyroid gland, making it useful pre-operatively and in thyroid storm.
thyroid gland (Wolff-Chaikoff effect)thyroid vasculature (in Graves' disease)
Indications
- thyroid storm (in combination with PTU and beta-blocker)
- preoperative preparation for thyroidectomy (reduce vascularity and hormone release)
- radiation emergency (blocking thyroid uptake of radioactive iodine)
- expectorant (off-label)
Contraindications
- hypothyroidism
- Hashimoto's thyroiditis
- iodine hypersensitivity
- Addison's disease
Adverse Effects
Common
- metallic taste
- sore teeth/gums
- headache
- GI upset
Serious
- iodism (chronic toxicity — parotitis, rash, mucous membrane irritation)
- thyroid dysfunction (hypothyroidism or escape phenomenon)
Pharmacokinetics (ADME)
| Absorption | rapidly and completely absorbed orally |
| Distribution | thyroid concentrates iodide |
| Metabolism | not metabolized; used directly as iodide |
| Excretion | renal |
| Half-life | not applicable |
| Onset | 1–2 hours (hormone release inhibition); days (vascularity reduction) |
| Peak | 1 day |
| Duration | days; escape phenomenon occurs after 10–14 days |
| Protein Binding | not applicable |
| Vd | moderate |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| antithyroid drugs (PTU, methimazole) | synergistic in thyroid storm; PTU/methimazole must be given 1 hour BEFORE iodide to prevent thyroid hormone synthesis from increased iodide substrate | moderate |
Nursing Considerations
- In thyroid storm protocol: administer antithyroid drug (PTU or methimazole) at least 1 hour BEFORE potassium iodide to prevent the iodide from being used for new hormone synthesis.
- Dilute SSKI in water or juice to reduce GI side effects and metallic taste.
- For radiation emergency use: administer within 4 hours before nuclear exposure; provide only one day's dose at a time for safety.
- The escape phenomenon (thyroid escapes Wolff-Chaikoff inhibition within 10–14 days) limits long-term iodide use as a sole antithyroid agent.
Clinical Pearls
- The sequence in thyroid storm is critical: antithyroid drug → wait 1 hour → iodide. Giving iodide first provides substrate for continued hormone synthesis, which the subsequent antithyroid drug cannot immediately block.
- Potassium iodide for radiation emergencies provides thyroidal uptake saturation — it protects the thyroid by blocking the uptake of radioactive iodine I-131, not by blocking all radiation.
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.