Orfadin (Nitisinone)

Orfadin is used in metabolic disorders that affect the tyrosine degradation pathway. It helps:

• Hereditary tyrosinemia type 1: reduces the accumulation of toxic metabolites and lowers risk of liver failure.
• Acute hepatic failure associated with tyrosinemia type 1: provides rapid biochemical control.
• Long‑term management of tyrosine‑related metabolic disorders: supports growth and development.
• Prevent of hepatic tumours in patients with tyrosinemia type 1.
• Adjunct to liver transplant pre‑conditioning in selected patients.

• Nitisinone inhibits the enzyme 4‑hydroxyphenylpyruvate dioxygenase (HPPD) in the hepatic tyrosine catabolic pathway. By blocking this step, the drug prevents formation of downstream toxic metabolites such as fumarylacetoacetate, thereby reducing liver injury and systemic complications associated with hereditary tyrosinemia type 1.

Side effects reported with nitisinone are generally mild to moderate and vary with duration of therapy.

Common Side Effects

• Elevated photocatalytic skin sensitivity to sunlight (photosensitivity risk).
• Mild headache or dizziness.
• Transient elevated liver‑function tests.
• Nausea or abdominal discomfort.
• Elevated plasma tyrosine levels requiring dietary monitoring.

Serious or Rare Side Effects

• Severe photosensitivity reactions, including blistering.
• Acute liver failure despite therapy.
• Progressive neurological deterioration.
• Severe allergic reactions such as anaphylaxis.
• Persistent elevation of serum tyrosine leading to ocular complications.

When prescribing Orfadin, clinicians should consider several safety measures.

• Monitor liver function: baseline and periodic testing is essential.
• Assess plasma tyrosine: dietary control may be required to keep levels within target range.
• Evaluate renal function: dose adjustment may be needed in severe impairment.
• Avoid concomitant photosensitising drugs: increased risk of skin reactions.
• Counsel patients on sun‑exposure protection.
• Store at ambient temperature: keep in original packaging, protect from moisture.

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