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Nitisinone (Orfadin®) is a competitive inhibitor of 4-hydroxyphenyl-pyruvate dioxygenase, an enzyme in the tyrosine catabolic pathway. By inhibiting the normal catabolism of tyrosine in patients with hereditary tyrosinemia type I (HT-1), nitisinone (Orfadin®) prevents the accumulation of catabolic intermediates, which would otherwise be converted to toxic metabolites. These toxic metabolites are responsible for the observed liver and kidney toxicity seen in these patients.
Fewer than 100 children in the United States are affected by HT-1. Because of liver failure or liver cancer, children with hereditary tyrosinemia type I rarely survive into their twenties without a liver transplant. However, for children treated early enough with nitisinone (Orfadin®), liver failure and liver cancer occur at much-reduced rates. Nitisinone (Orfadin®) was studied in more than 180 patients with a median age of 9 months when therapy was started. When the drug was combined with a restricted diet, the 4-year survival rate of children under 2 months of age at the time of diagnosis was 88 percent. Historical data for children treated with dietary restrictions alone shows a survival rate of 29 percent for the same time period.
Nitisinone (Orfadin®) must be used in conjunction with a diet restricted in the amino acids tyrosine and phenylalanine. High tyrosine levels may be toxic to eyes, skin and the nervous system. The most common side effects of the drug were related to high tyrosine levels due to patients not eating the appropriate foods as well as rare cases of mild reductions in platelet and white blood cell counts.
Nitisinone (Orfadin®) should be prescribed by physicians experienced in treating hereditary tyrosinemia type I, as the correct dose must be adjusted for each patient according to specific biochemical tests. Access to a nutritionist skilled in managing children with inborn errors of metabolism requiring a low protein diet is an important part of therapy. Blood tests should be monitored regularly to maintain the correct dose for that patient and to monitor for potential adverse events.
FDA APPROVED INDICATION
Nitisinone (Orfadin®) is indicated as an adjunct to dietary restriction of tyrosine and pheneylalanine in the treatment of hereditary tyrosinemia type I.
Generic Name: Nitisinone
Prior authorization is required.
Nitisinone (Orfadin®) is considered medically necessary for the treatment of hereditary tyrosinemia type 1.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
4/16/2002: Approved by Pharmacy & Therapeutics (P & T) Committee
9/12/2006: Updated Accredo contact information
9/21/2006: Coding updated. ICD9 2006 revisions added to policy.
1/3/2007: Code reference section updated per the 2007 CPT/HCPCS revisions.
01/01/2009: Accredo preferred provider information removed. BCBSMS information added.
04/02/2014: Policy reviewed; no changes. Removed deleted ICD-9 Diagnosis code 775.8 from the Code Reference section.
Orfandin® Prescribing Information (revised 09-12-2006)
This may not be a comprehensive list of procedure codes applicable to this policy.
The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.