SODIUM POLYSTYRENE SULFONATE

Chemistry - A sulfonated cation exchange resin, sodium polystyrene sulfonate (SPS) occurs as agolden brown, fine powder. It is odorless and tasteless. Each gram contains 4.1 mEq of sodium andhas an in vitro exchange capacity of about 3.1 mEq of potassium (in actuality a maximum of 1 mEqis usually exchanged)..

Storage, Stability, Compatibility

Store products in well-closed containers at room temperature;do not heat. Suspensions should be freshly prepared and used within 24 hours.

Pharmacology - SODIUM POLYSTYRENE SULFONATE

SPS is a resin that exchanges sodium for other cations. After being given orally, hydrogen ions will be exchanged for sodium (in an acidic environment). As the resin travelsthrough the intestinal tract, the hydrogen ions will be exchanged with other more concentratedcations. Primary exchange with potassium occurs predominantly in the large intestine. When givenas a retention enema, SPS generally exchanges sodium for potassium directly in the colorectum.
While theoretically, up to 3.1 mEq of potassium could be exchanged per gram of SPS, it is unlikelythat more than one mEq will be exchanged per gram of resin administered.

Uses, Indications

SPS is indicated as adjunctive treatment of hyperkalemia. The cause of thehyperkalemia should be elucidated and corrected if possible.

Pharmacokinetics - SODIUM POLYSTYRENE SULFONATE

SPS is not absorbed from the GI tract. Its onset of action may be from hoursto days, so severe hyperkalemia may require other treatments (e.g., dialysis) in the interim.

Contraindications, Precautions, Reproductive Safety

Because large quantities of sodium maybe released and absorbed, patients on severely restricted sodium diets (severe CHF, hypertension, oliguria) may benefit from alternative methods of treatment. Overdosage/overuse may lead tohypokalemia, hypocalcemia and hypomagnesemia.
While reproductive studies have apparently not been performed, it is unlikely the drug carriesmuch teratogenic potential.

Adverse Effects, Warnings

Large doses may cause constipation (fecal impactions have beenreported rarely), anorexia, vomiting or nausea. Dose related hypocalcemia, hypokalemia and sodiumretention have also been noted. To hasten the drug's action and to prevent constipation, SPS isgenerally mixed with 70% sorbitol (3-4 ml per one gram of resin).
Overdosage, Acute Toxicity - Overdosage may cause the adverse effects noted above. Treatsymptomatically.

Drug Interactions

SPS may bind with magnesium or calcium found in laxatives (milk ofmagnesia, magnesium sulfate, etc.) or antacids which can prevent bicarbonate ion neutralizationand lead to metabolic alkalosis. Concurrent use is not recommended during SPS therapy.