Efficacy & Safety of Oral Adjuvants to Phototherapy in Neonatal Hyperbilirubinemia

Neonatal jaundice, or neonatal hyperbilirubinemia, is the most common medical issue in the first two weeks of life and is a frequent cause of prolonged hospitalization and readmission to the hospital after birth. It results from elevated total serum bilirubin (TSB) and is clinically manifested as yellowish discoloration of the skin, sclera, and mucous membrane. Increased enterohepatic circulation of indirect bilirubin is one of the elucidated mechanisms implicated in the pathophysiology of neonatal hyperbilirubinemia.

Clinical jaundice appears in about 60% of term neonates and 80% of preterms within the first week of life. In most cases, it is a mild, transient, and self-limiting condition that resolves spontaneously and is referred to as "physiological jaundice.". When bilirubin levels increase by more than 5 mg/dL/day or more than 0.2 mg/dL/hour, or when jaundice lasts longer than two to three weeks in full-term infants, pathologic hyperbilirubinemia is said to have occurred. In preterm infants, unconjugated hyperbilirubinemia is of particular concern, given that their blood-brain barrier is more permeable, and their underdeveloped brain is more susceptible to bilirubin-induced neurotoxicity.

Scavenging unconjugated plasma bilirubin can be done, conveniently, non-invasively, and effectively by phototherapy. Phototherapy is universally recognized as the mainstay for the treatment of neonatal jaundice and is widely used in neonatal units and postnatal wards. It is a safe and effective method for decreasing or preventing the rise of serum unconjugated bilirubin levels, and it reduces the need for exchange transfusions in neonates.

However, phototherapy has both immediate and long-term side effects, such as rash, bronze baby syndrome, and circadian rhythm modification. This is coupled with social side effects like parental concern because of the infant's increased hospitalization, broken mother-infant attachment, and high cost of care. Moreover, phototherapy can only decrease already accumulated UCB but does not prevent its accumulation. Exchange transfusion therapy, which is generally performed after the failure of phototherapy, may lead to severe complications, such as embolism, sepsis, necrotizing enterocolitis, or even death.

Consequently, there is a growing potential to explore novel adjuvant treatments that can help to increase bilirubin clearance, decrease phototherapy duration, and decrease exchange transfusion rate.

One of the methods used to treat indirect hyperbilirubinemia is to use a zinc solution. Studies have shown that chronic or acute use of zinc salts can reduce serum bilirubin levels by inhibiting the enterohepatic cycle of indirect bilirubin. Oral administration of zinc (Zn) sulfate increases bilirubin excretion and decreases its serum level.

Oral administration of Zn salts is possible in two dose ranges: low (10 mg/day) and high (11-20 mg/day). Given that some of the medication is absorbed in the proximal ileum, giving a high dose may be desirable. Zn salts are safe, and studies treating several children and newborns with diarrhea, measles, pneumonia, the common cold, and malaria have demonstrated the safety of oral Zn sulfate administration. Studies conducted on the effectiveness of Zn salts on serum indirect bilirubin levels in newborns have yielded different results, all calling for further research. Additionally, neonates with hyperbilirubinemia appear to have lower serum Zn levels than other well-term neonates.

The efficacy of ursodeoxycholic acid as an adjuvant to phototherapy has also been examined in a few studies. Ursodeoxycholic acid (UDCA), or ursodiol, is a bile acid commonly used to manage cholestatic liver disease. UDCA helps in improving endogenous bile secretion, reducing the reducing the displacement of more toxic components of endogenous bile acids, and reducing enterohepatic circulation. Because of its anti-apoptotic, anti-inflammatory, and antioxidant characteristics, UDCA also has hepatoprotective and neuroprotective effects.

Although UDCA is an off-label treatment in neonates, it is widely used in conjugated hyperbilirubinemia and liver disorders. UDCA has also been investigated for its possible role in indirect hyperbilirubinemia. It is thought to function by inhibiting the reabsorption of bilirubin from the intestines. UDCA is often tolerated well. In studies on healthy-term neonates, ill neonates, and neonates with G6PD deficiency, UDCA was reported to be useful in shortening the length of phototherapy.