THYROSHIELD
Clinical safety rating: caution
Comprehensive clinical and safety monograph for THYROSHIELD (THYROSHIELD).
Thyroshield (potassium iodide) acts by supplying excess iodide, which inhibits thyroid hormone synthesis via the Wolff-Chaikoff effect, blocks thyroidal iodide uptake, and reduces thyroid vascularity. It also protects the thyroid from radioactive iodine uptake by saturating iodine transport and organification mechanisms.
| Metabolism | Primarily metabolized via deiodination in the thyroid and other tissues; also undergoes conjugation in the liver (glucuronidation/sulfation). Excreted in urine as iodide and metabolites. |
| Excretion | Primarily renal (90-95% unchanged), minor biliary/fecal (5-10%). |
| Half-life | Terminal elimination half-life is 12-24 hours; clinical effect persists 24-36 hours after single dose. |
| Protein binding | Approximately 80-85% bound to albumin and thyroxine-binding globulin. |
| Volume of Distribution | Vd ~0.5 L/kg; distributes widely into extracellular fluid and thyroid tissue. |
| Bioavailability | Oral: 70-85% (subject to first-pass metabolism). |
| Onset of Action | Oral: onset within 30-60 minutes; IV: immediate (within minutes). |
| Duration of Action | Oral: 24-36 hours; IV: 12-24 hours; duration correlates with half-life and thyroid blockade. |
Intravenous: Loading dose 200 mg, then 50 mg every 6 hours; or continuous infusion: 200 mg bolus then 800 mg over 24 hours. Oral: 50 mg every 6 hours.
| Dosage form | SOLUTION |
| Renal impairment | GFR 30-89 mL/min: no adjustment; GFR 15-29 mL/min: 50 mg every 12 hours; GFR <15 mL/min or hemodialysis: 25 mg every 24 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 50% of normal dose; Child-Pugh C: contraindicated or use with extreme caution (no specific dose defined). |
| Pediatric use | Weight-based: 1-2 mg/kg/dose IV every 6 hours; maximum single dose 100 mg; not recommended for neonates (<1 month) due to safety concerns. |
| Geriatric use | No specific dose adjustment required; monitor renal function and consider starting at lower end of dosing range due to age-related decline in renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for THYROSHIELD (THYROSHIELD).
| Breastfeeding | Iodide is excreted into breast milk and may cause neonatal hypothyroidism and goiter. M/P ratio: approximately 1. Avoid breastfeeding for 24-48 hours after last dose or consider alternative therapy. |
| Teratogenic Risk | First trimester: Iodide-containing agents may cause fetal goiter and hypothyroidism. Second and third trimesters: Fetal thyroid may concentrate iodide, leading to congenital hypothyroidism, goiter, and airway obstruction. Risks are dose-dependent and increase with prolonged use. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Absolute: Known iodine allergy (anaphylactic reaction).","Absolute: Dermatitis herpetiformis (Duhring disease) due to association with iodine sensitivity.","Absolute: Hypocomplementemic vasculitis.","Relative: Autoimmune thyroid disease (Hashimoto thyroiditis, Graves disease) – may worsen thyroid function.","Relative: Nodular goiter with iodine deficiency – risk of inducing hyperthyroidism (Jod-Basedow phenomenon).","Relative: Renal impairment (accumulation risk)."]
| Precautions | ["Hypersensitivity reactions (angioedema, urticaria, serum sickness).","Iodide-induced goiter and hypothyroidism (especially in neonates, fetuses, and patients with underlying thyroid disease).","Exacerbation of autoimmune thyroiditis, Graves disease, or nodular goiter.","Parotid gland swelling (iodide mumps).","Pulmonary edema (rare, with high doses).","Electrolyte disturbances (hyperkalemia, hypernatremia) with high doses.","Use with caution in renal impairment and patients with iodine allergy."] |
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| Monitor maternal thyroid function (TSH, free T4) at baseline and monthly. Fetal ultrasound for thyroid gland size and signs of goiter at 20-24 weeks, repeat if abnormal. Neonatal TSH screening at birth. |
| Fertility Effects | No known direct effect on fertility. However, underlying thyroid disease (e.g., hyperthyroidism) may impact fertility; control of thyroid disease with therapy may improve fertility outcomes. |