Clinical trials are ongoing to test whether nitisinone can prevent ochronosis experienced by older alkaptonuria patients. History
Nitisinone was discovered as part of a program to develop a class of herbicides called HPPD inhibitors. It is a member of the benzoylcyclohexane-1,3-dione family of herbicides, which are chemically derived from a natural phytotoxin, leptospermone, obtained from the Australian bottlebrush plant (Callistemon citrinus). HPPD is essential in plants and animals for catabolism, or breaking apart, of tyrosine. In plants, preventing this process leads to destruction of chlorophyll and the death of the plant. In toxicology studies of the herbicide, it was discovered that it had activity against HPPD in rats and humans.In Type I tyrosinemia, a different enzyme involved in the breakdown of tyrosine, fumarylacetoacetate hydrolase is mutated and doesnt work, leading to very harmful products building up in the body. Fumarylacetoacetate hydrolase acts on tyrosine after HPPD does, so scientists working on making herbicides in the class of HPPD inhibitors hypothesized that inhibiting HPPD and controlling tyrosine in the diet could treat this disease. A series of small clinical trials attempted with one of their compounds, nitisinone, were conducted and were successful, leading to nitisinone being brought to market as an orphan drug  Swedish Orphan International, which was later acquired by Swedish Orphan Biovitrum (Sobi). In 201, Cycle Pharmaceuticals launched Nityr in the United States through Cycle Vita. Research
Nitisinone is being studied as a treatment for alkaptonuria. References
External links
"Nitisinone". Drug Information Portal. U.S. National Library of Medicine.
CT angiography and MR angiography are more or less equivalent when used to diagnose or exclude vertebral artery dissection. CTA has the advantage of showing certain abnormalities earlier, tends to be available outside office hours, and can be performed rapidly. When MR angiography is used, the best results are achieved in the T1 setting using a protocol known as "fat suppression". Doppler ultrasound is less useful as it provides little information about the part of the artery close to the skull base and in the vertebral foramina, and any abnormality detected on ultrasound would still require confirmation with CT or MRI. Treatment
Treatment is focused on reducing stroke episodes and damage from a distending artery. Four treatment modalities have been reported in the treatment of vertebral artery dissection. The two main treatments involve medication: anticoagulation (using heparin and warfarin) and antiplatelet drugs (usually aspirin). More rarely, thrombolysis (medication that dissolves blood clots) may be administered, and occasionally obstruction may be treated with angioplasty and stenting. No randomized controlled trials have been performed to compare the different treatment modalities. Surgery is only used in exceptional cases. Anticoagulation and aspirin
From analysis of the existing small treatment trials of cervical artery dissection (carotid and vertebral) it appears that aspirin and anticoagulation (heparin followed by warfarin) are equally effective in reducing the risk of further stroke or death. Anticoagulation is regarded as more powerful than antiplatelet therapy, but anticoagulants may increase the size of the hematoma and worsen obstruction of the affected artery.