Give me drugs acting on raised bilirubin
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Drugs Acting on Raised Bilirubin (Hyperbilirubinemia)
The approach to treating raised bilirubin depends entirely on the underlying cause and type (unconjugated vs. conjugated, prehepatic vs. hepatic vs. posthepatic). There is no single "anti-bilirubin" drug - each agent targets a specific mechanism.
1. Phenobarbital
Mechanism: A potent inducer of the constitutive androstane receptor (CAR), which upregulates UGT1A1 (UDP-glucuronosyltransferase) expression in hepatocytes, thereby increasing bilirubin conjugation. It also induces cytochrome P450-dependent microsomal enzymes that enhance bilirubin metabolism.
Uses:
- Crigler-Najjar Syndrome Type II - the treatment of choice; reduces serum bilirubin levels to 3-5 mg/dL (from up to 20-45 mg/dL). Bilirubin levels typically fall to the range where kernicterus risk is low. (Sleisenger & Fordtran, Goldman-Cecil Medicine)
- Neonatal physiologic jaundice - may be administered as a promoter of bilirubin metabolism, though phototherapy is preferred.
- No effect in Crigler-Najjar Type I (UGT1A1 is completely absent, so there is nothing to induce).
Note: Also reduces bilirubin in Gilbert syndrome, though no treatment is needed there.
2. Phototherapy (Blue Light)
Not a drug, but the primary therapeutic intervention for neonatal hyperbilirubinemia. Blue light (wavelength ~450-460 nm) converts unconjugated bilirubin into water-soluble photoisomers that can be excreted in bile without glucuronidation. Used as a bridge to liver transplantation in Crigler-Najjar Type I. (Robbins & Kumar Basic Pathology; Harper's Illustrated Biochemistry)
3. Ursodeoxycholic Acid (UDCA)
Mechanism: A hydrophilic bile acid that replaces toxic hydrophobic bile acids in the enterohepatic circulation, improves bile flow (choleretic), and has hepatoprotective and anti-apoptotic effects.
Uses in hyperbilirubinemia:
- Intrahepatic cholestasis of pregnancy - first-line treatment; improves bilirubin levels and liver function tests, and relieves pruritus. Dose: 300 mg PO every 8 hours until delivery. (Rosen's Emergency Medicine; Frameworks for Internal Medicine)
- Primary biliary cholangitis (PBC) - reduces serum bilirubin and hepatic inflammation.
- Post-hematopoietic cell transplantation cholestasis / GVHD-related cholestasis - prophylactic UDCA reduces frequency of cholestasis and improves outcomes vs placebo. (Sleisenger & Fordtran)
4. Cholestyramine (Bile Acid Sequestrant)
Mechanism: An anion-exchange resin that binds bile salts in the intestine, preventing their enterohepatic reabsorption. Reduces the bile acid load contributing to cholestatic symptoms.
Use: Primarily relieves pruritus in obstructive jaundice and cholestatic liver disease (20-50% of jaundiced patients have pruritus). Does not directly lower serum bilirubin but manages the cholestasis-associated symptom burden. (Andrews' Diseases of the Skin)
5. Rifampicin
Dual role - cause AND treatment:
- At standard doses, rifampicin can cause unconjugated hyperbilirubinemia by competitively inhibiting sinusoidal transport protein OATP1B1, reducing hepatocellular uptake of bilirubin.
- In cholestatic pruritus (e.g., intrahepatic cholestasis of pregnancy refractory cases), rifampicin is used in combination with UDCA - it induces nuclear receptors that accelerate bile acid detoxification. (Sleisenger & Fordtran; Andrews' Diseases of the Skin)
6. Drugs That Cause or Worsen Hyperbilirubinemia (Important to Recognize and Avoid)
| Drug | Mechanism |
|---|---|
| Rifampicin, Cyclosporine A | Inhibit OATP1B1 - reduce hepatocellular bilirubin uptake |
| Estrogens (OCP) | Worsen Dubin-Johnson syndrome (impair conjugated bilirubin export); contraindicated |
| Valproate | Hepatotoxicity - raises bilirubin as a sign of liver injury |
| Irinotecan | Requires UGT1A1 for glucuronidation; Gilbert syndrome patients have increased toxicity risk |
Summary Table
| Drug | Bilirubin Type Targeted | Mechanism | Clinical Use |
|---|---|---|---|
| Phenobarbital | Unconjugated | Induces UGT1A1 (via CAR) | Crigler-Najjar Type II, neonatal jaundice |
| Phototherapy | Unconjugated | Converts bilirubin to soluble isomers | Neonatal jaundice, Crigler-Najjar Type I bridge |
| UDCA | Both (cholestatic) | Replaces toxic bile acids, improves bile flow | ICP of pregnancy, PBC, post-HCT cholestasis |
| Cholestyramine | Indirect (cholestatic) | Binds bile acids in gut | Pruritus in obstructive jaundice |
| Rifampicin | Cholestatic | Nuclear receptor induction | Refractory cholestatic pruritus |
Key point: No drug directly "removes" circulating bilirubin. All agents work by either increasing conjugation/excretion, improving bile flow, or targeting the underlying condition causing the bilirubin rise. Definitive treatment always requires addressing the root cause - whether hemolysis, hepatocellular disease, biliary obstruction, or a congenital enzyme defect.
- Sleisenger and Fordtran's Gastrointestinal and Liver Disease, pp. 336-338 (Table 21.2, Hereditary Disorders of Bilirubin Metabolism)
- Goldman-Cecil Medicine, pp. 860, 942-951
- Harper's Illustrated Biochemistry, 32nd Ed, pp. 1968-1991
- Rosen's Emergency Medicine; Andrews' Diseases of the Skin, p. 2470-2474
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