Sodium polystyrene sulfonate (SPS) is approved by the Food and Drug Administration (FDA) for the treatment of hyperkalemia though it is not typically the first-line treatment.[1] Potassium level greater than 5 mEq/L qualifies as hyperkalemia. Hyperkalemia is often asymptomatic; however, it may cause fatigue, muscle cramps, muscle weakness, rarely paralysis. A high level of potassium is associated with an increase in morbidity and mortality, especially K > 6.5 mEq/L can be fatal. Hence, prompt management is essential to avoid serious consequences.  Sodium polystyrene sulfonate helps by removing extra potassium from the body. Due to its slow onset of action, it is a second-line agent in emergent situations. Data on the non-FDA approved use of this drug is limited. This drug can also help to remove excess calcium, sodium from solutions in technical applications.[2][3][4][5][6][7]

Sodium polystyrene sulfonate (SPS) is an insoluble polymer cation-exchange resin. After ingestion of oral formulation or application through the rectal route, this resin exchanges sodium with potassium ions from the intestinal cells. Then the potassium binds with SPS, continues to move through the gastrointestinal tract, and finally eliminated in the feces.[8][9] But sodium polystyrene sulfonate is not selective for potassium; it may bind with calcium and magnesium.[10] This drug begins its action within 2 to 24 hrs of its administration and continues its work up to 4 to 6 hours before it gets eliminated from the body through feces.[11] The exchange capacity of SPS is approximately 33% or 1 mEq of potassium per 1 gram of resin, and this number is not constant. It may be as low as 0.4 to 0.8 mEq/gram of SPS resin. Competition from other cations, especially sodium, calcium, and magnesium, contributes to this reduction of this exchange capacity.

Sodium polystyrene sulfonate can be administered either orally or rectally. It is available in oral suspension, oral powder formulation, and rectal enema formulation. Appropriate dosing of sodium polystyrene sulfonate is varying on the route of administration. Usually, the dose of sodium polystyrene sulfonate is between 15 g (60 mL) to 60 g (240 mL), and each 15 g of sodium polystyrene sulfonate can bind 15 mEq of potassium.[12] While using as an oral suspension, it should not be heated or should not be used along with heated foods or liquids, because this may cause a decrease in the effectiveness of this drug. This drug should not be mixed with banana or orange juice (potassium-rich). SPS may impair the absorption of other orally administered medications and may lead to reduced efficacy, so other oral drugs should be administered at least 3 hours before or 3 hours after SPS therapy. Patients with gastroparesis may require a longer period between SPS and other oral medications. When using an enema, the administration of a cleansing enema should be before administering sodium polystyrene sulfonate. It should be as warm as body temperature for rectal formulation. After administration, SPS should be retained in the colon for at least 30 to 60 min. After completing retention, to remove remaining resin, irrigation should be done with nonsodium colonic irrigant. In the past, SPS used to be coadministered with sorbitol to reduce the chance of constipation, but in 2009, the FDA issued a warning against the concomitant use of SPS and sorbitol, due to occurrence of colonic necrosis and other serious GI side effects. Nowadays, the concurrent use of sorbitol is not recommended.[13] 

Storage:

Resin powder should be stored at 25 degrees C (77 F); excursions permitted to 15 to 30 degrees C (59 to 86 F). After the preparation of suspension, it should be used within 24 hours.

Sodium polystyrene sulfonate has several side effects.[14][15] Some are mild and should eventually resolve spontaneously; others are serious and need urgent care. 

Mild adverse effect:

• Diarrhea
• Nausea
• Vomiting
• Loss of appetite

Serious side effects are:

• Ischemic colonic necrosis
• Constipation 
• Seizures
• Confusion
• Muscle weakness
• Abdominal pain
• Irregular heartbeat

SPS is contraindicated in the following conditions: 

• Hypokalemia
• Previous history of hypersensitivity to polystyrene sulfonate resins
• Bowel Obstruction
• Neonates with reduced gut motility

Cautions:

SPS can contribute to sodium overload and lead to fluid retention. Hence, SPS use requires caution in certain conditions such as congestive heart failure, severe hypertension, and marked edema. Clinicians should not use SPS in patients who have abnormal bowel functions, such as bowel obstruction, Ileus, and postoperative patients. Using SPS in these patients may increase the risk of bowel ischemia, necrosis, and serious constipation.

Pregnancy and Lactation:

SPS does not get absorbed systemically; thus, maternal use of SPS is not expected to cause harm to the fetus. Similarly, as it is not secreted through breast milk, breastfeeding is not expected to result in any particular risk to the newborn.