Potassium Iodide / Lugol's Solution

How it works

High iodide concentrations transiently inhibit thyroid hormone release and synthesis (the Wolff-Chaikoff effect) and reduce thyroid gland vascularity, producing a rapid but temporary fall in circulating thyroid hormone.

Prescribing in practice

• The effect is transient and iodide can ultimately worsen hyperthyroidism, so it is used short term and generally after starting an antithyroid drug rather than as sole or long-term therapy.
• In thyroid storm it is given after a thionamide has been started to avoid providing fresh substrate for hormone synthesis.
• Dilute well and give orally; avoid in iodine hypersensitivity and use caution in pregnancy because iodide crosses the placenta.

Monitoring

Monitor thyroid function and clinical status, as the suppressive effect is short-lived and may escape with continued use.

Counselling the patient

• Take the diluted solution as directed, typically with or after food to reduce gastric irritation.
• Report a metallic taste, rash, swelling of the salivary glands, or worsening symptoms.
• This is a short-term treatment used as part of a wider plan for your thyroid.

Evidence & guidelines

Iodide-induced inhibition of thyroid hormone release underpins its established role in surgical preparation and thyroid storm management.