POTASSIUM IODIDE

POTASSIUM IODIDE
(poe-tass'ee-um)
Pima, SSKI, Thyro-Block 
Classifications: antithyroid agent; expectorant;
Therapeutic: antithyroid
; expectorant
Prototype: Guaifenesin
Pregnancy Category: D

Availability

325 mg/5 mL syrup; 1 g/mL solution

Action

Pharmacologic use primarily related to iodide portion of molecule. Appears to increase secretion of respiratory fluids by direct action on bronchial tissue, thereby decreasing mucus viscosity. If patient is euthyroid, excess iodide ions causes minimal change in thyroid gland mass. Conversely, when the thyroid gland is hyperplastic, excess iodide ions temporarily inhibit secretion of thyroid hormone, foster accumulation in thyroid follicles, and decrease vascularity of gland.

Therapeutic Effect

Potassium iodide administration for hyperthyroidism is limited to short-term therapy. As an expectorant, the iodine ion increases mucous secretion formation in the bronchi, and decreases viscosity of the mucus.

Uses

To facilitate bronchial drainage and cough in emphysema, asthma, chronic bronchitis, bronchiectasis, and respiratory tract allergies characterized by difficult-to-raise sputum. Also used alone for hyperthyroidism or in conjunction with antithyroid drugs and propranolol in treatment of thyrotoxic crisis; in immediate preoperative period for thyroidectomy to decrease vascularity, fragility, and size of thyroid gland and for treatment of persistent or recurring hyperthyroidism that occurs in Graves' disease patients. Used as a radiation protectant in patients receiving radioactive iodine and to shield the thyroid gland from radiation in the wake of a serious nuclear plant accident. (Use as an expectorant has been largely replaced by other agents.)

Contraindications

Hypersensitivity or idiosyncrasy to iodine; hyperthyroidism; hyperkalemia; acute bronchitis; pregnancy (category D), lactation.

Cautious Use

Renal impairment; cardiac disease; pulmonary tuberculosis; Addison's disease.

Route & Dosage

To Reduce Thyroid Vascularity
Adult/Child: PO 50–250 mg t.i.d. for 10–14 d before surgery

Expectorant
Adult: PO 300–650 mg p.c. b.i.d. or t.i.d.
Child: PO 60–250 mg p.c. b.i.d. or t.i.d.

Thyroid Blocking in Radiation Emergency
Adult: PO 130 mg/d for 10 d
Child: PO <1 y, 65 mg/d for 10 d; >1 y, 130 mg/d for 10 d

Administration

Oral
  • Give with meals in a full glass (240 mL) of water or fruit juice and at bedtime with food or juice to disguise salty taste and minimize gastric distress.
  • Avoid giving KI with milk; absorption of the drug may be decreased by dairy products.
  • Adhere strictly to schedule and accurate dose measurements when iodide is administered to prepare thyroid gland for surgery, particularly at end of treatment period when possibility of "escape" (from iodide) effect on thyroid gland increases.
  • Place container in warm water and gently agitating to dissolve if crystals are noted in the solution.
  • Discard any solution that has turned a brownish yellow on standing, especially if exposed to light (caused by liberated trace of free iodine).
  • Store in airtight, light-resistant container.

Adverse Effects (≥1%)

GI: Diarrhea, nausea, vomiting, stomach pain, nonspecific small bowel lesions (associated with enteric coated tablets). Body as a Whole: Angioneurotic edema, cutaneous and mucosal hemorrhage, fever, arthralgias, lymph node enlargement, eosinophilia, paresthesias, periorbital edema, weakness. Iodine poisoning (iodism): Metallic taste, stomatitis, salivation, coryza, sneezing; swollen and tender salivary glands (sialadenitis), frontal headache, vomiting (blue vomitus if stomach contained starches, otherwise yellow vomitus), bloody diarrhea. Metabolic: Hyperthyroid adenoma, goiter, hypothyroidism, collagen disease–like syndromes. CV: Irregular heartbeat. CNS: Mental confusion. Skin: Acneiform skin lesions (prolonged use), flare-up of adolescent acne. Respiratory: Productive cough, pulmonary edema.

Diagnostic Test Interference

Potassium iodide may alter thyroid function test results and may interfere with urinary 17-OHCS determinations.

Interactions

Drug: antithyroid drugs, lithium may potentiate hypothyroid and goitrogenic actions; potassium-sparing diuretics, potassium supplements, ace inhibitors increase risk of hyperkalemia.

Pharmacokinetics

Absorption: Adequately absorbed from GI tract. Distribution: Crosses placenta. Elimination: Cleared from plasma by renal excretion or thyroid uptake.

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Determine serum potassium levels before and periodically during therapy.
  • Keep physician informed about characteristics of sputum: quantity, consistency, color.

Patient & Family Education

  • Report to physician promptly the occurrence of GI bleeding, abdominal pain, distension, nausea, or vomiting.
  • Report clinical S&S of iodism (see ADVERSE EFFECTS). Usually, symptoms will subside with dose reduction and lengthened intervals between doses.
  • Avoid foods rich in iodine if iodism develops: Seafood, fish liver oils, and iodized salt.
  • Be aware that sudden withdrawal following prolonged use may precipitate thyroid storm.
  • Do not use OTC drugs without consulting physician. Many preparations contain iodides and could augment prescribed dose [e.g., cough syrups, gargles, asthma medication, salt substitutes, cod liver oil, multiple vitamins (often suspended in iodide solutions)].
  • Be aware that optimum hydration is the best expectorant when taking KI as an expectorant. Increase daily fluid intake.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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