Drug Groups

approved; investigational

Description

Nitisinone is a synthetic reversible inhibitor of 4-hydroxyphenylpyruvate dioxygenase. It is used in the treatment of hereditary tyrosinemia type 1. It is sold under the brand name Orfadin. [Wikipedia]

Indication

Used as an adjunct to dietary restriction of tyrosine and phenylalanine in the treatment of hereditary tyrosinemia type 1.

Pharmacology

Hereditary tyrosinemia type 1 occurs due to a deficiency in fumarylacetoacetase (FAH), the final enzyme in the tyrosine catabolic pathway. Nitisinone inhibits catabolism of tyrosine by preventing the catabolic intermediates. In patients with HT-1, these catabolic intermediates are converted to the toxic metabolites succinylacetone and succinylacetoacetate, which are responsible for the observed liver and kidney toxicity. Succinylacetone can also inhibit the porphyrin synthesis pathway leading to the accumulation of 5-aminolevulinate, a neurotoxin responsible for the porphyric crises characteristic of HT-1.

Toxicity

Side effects include elevated plasma levels of this amino acid, hepatic and liver failure.

Affected Organisms

Absorption

The capsule and liquid formulations are bioequivalent in both the plasma concentration-time curve and maximum plasma concentration (Cmax).

Half Life

~54 hours

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