POTASSIUM IODIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for POTASSIUM IODIDE (POTASSIUM IODIDE).
Potassium iodide suppresses thyroid hormone synthesis and release via the Wolff-Chaikoff effect, inhibiting iodide organification and reducing vascularity of the thyroid gland.
| Metabolism | Minimal hepatic metabolism; primarily excreted renally as iodide. |
| Excretion | Renal: >90% of absorbed iodide is excreted in urine; fecal elimination is negligible (<2%). |
| Half-life | Terminal half-life in euthyroid individuals is approximately 13 days (range 10–15 days). In hyperthyroidism, half-life may be shortened to 5–6 days due to increased thyroid clearance; in hypothyroidism, half-life may be prolonged up to 40 days. |
| Protein binding | Not significantly protein-bound (<5%); iodide distributes freely in extracellular fluid and is actively transported into thyroid follicular cells. |
| Volume of Distribution | Approximately 0.2–0.4 L/kg, reflecting distribution primarily in extracellular fluid and thyroid gland; does not significantly penetrate cells except via active transport into thyroid. |
| Bioavailability | Oral: 100% (rapidly and completely absorbed from the gastrointestinal tract). |
| Onset of Action | Oral: Antithyroid effect (reduction of thyroid hormone release) begins within 24–48 hours; maximal effect on thyroid vascularity and hormone release occurs after 10–14 days of continuous therapy. Radioprotective effect (thyroid blockade) requires administration 2–24 hours prior to radioactive iodine exposure. |
| Duration of Action | Antithyroid effect: Lasts as long as therapy is continued, typically 2–4 weeks for preoperative preparation. After discontinuation, thyroid hormone release normalizes within 2–3 weeks. Radioprotective effect: Single oral dose provides thyroid blockade for approximately 24–48 hours. |
Oral: 300 mg (0.3 mL of saturated solution) three times daily for thyroid protection in radiation exposure; for hyperthyroidism preoperative: 60-250 mg (0.06-0.25 mL) three times daily.
| Dosage form | SOLUTION |
| Renal impairment | No specific dose adjustment recommended for renal impairment; use with caution in severe renal insufficiency due to potential iodide accumulation. |
| Liver impairment | No specific dose adjustment recommended for hepatic impairment. |
| Pediatric use | Neonates and infants: 16 mg (0.016 mL) once daily; Children 1 month to 3 years: 32 mg (0.032 mL) once daily; Children 3-12 years: 65 mg (0.065 mL) once daily; Adolescents >12 years: 130 mg (0.13 mL) once daily; all doses given orally for radiation emergencies. |
| Geriatric use | No specific dose adjustment required; monitor renal function and thyroid status as elderly may be more susceptible to iodide-induced hypothyroidism. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for POTASSIUM IODIDE (POTASSIUM IODIDE).
| Breastfeeding | Potassium iodide is excreted into breast milk and may reach concentrations higher than maternal plasma (M/P ratio not established). Breastfeeding infants are at risk of iodine-induced hypothyroidism or goiter. Avoid use during breastfeeding unless clearly needed for maternal indication (e.g., radiation emergency). |
| Teratogenic Risk | First trimester: Iodide crosses placenta; high doses may cause fetal goiter and hypothyroidism. Second trimester: Risk of fetal thyroid suppression with chronic high-dose exposure. Third trimester: Fetal thyroid may be more sensitive; iodine overload can lead to neonatal goiter and airway obstruction. Use lowest effective dose for short duration. |
■ FDA Black Box Warning
None
| Serious Effects |
["Absolute: Known hypersensitivity to iodine","Absolute: Dermatitis herpetiformis","Absolute: Hypocomplementemic vasculitis"]
| Precautions | ["May cause hypothyroidism in susceptible individuals","Use with caution in patients with autoimmune thyroiditis","Risk of iodine-induced hyperthyroidism (Jod-Basedow phenomenon)","Avoid in patients with pulmonary edema or compromised airway due to potential bronchospasm"] |
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| Fetal Monitoring | Monitor maternal thyroid function (TSH, free T4) before and during therapy. Fetal ultrasound to assess thyroid size and anatomy if used long-term. Neonatal thyroid screening at birth. Assess for signs of iodine toxicity (metallic taste, salivary gland swelling, gastrointestinal upset). |
| Fertility Effects | No direct effects on fertility reported at therapeutic doses. High doses causing hypothyroidism may impair ovulation and spermatogenesis; effect is reversible upon correction of thyroid status. |