Molecule

Drug Groups

approved; investigational

Description

Droxidopa is a precursor of noradrenaline that is used in the treatment of Parkinsonism. It is approved for use in Japan and is currently in trials in the U.S. The racaemic form (dl-threo-3,4-dihydroxyphenylserine) has also been used, and has been investigated in the treatment of orthostatic hypotension. There is a deficit of noradrenaline as well as of dopamine in Parkinson's disease and it has been proposed that this underlies the sudden transient freezing seen usually in advanced disease.

Indication

For treatment of neurogenic orthostatic hypotension (NOH) associated with various disorders including Multiple System Atrophy, Familial Amyloid Polyneuropathy, hemodialysis induced hypotension and Parkinson's Disease. Also investigated for use/treatment in neurologic disorders, nephropathy, blood (blood forming organ disorders, unspecified), and dizzy/fainting spells.

Pharmacology

Droxidopa is an orally active synthetic precursor of norepinephrine that increases the deficient supply of norepinephrine in patients with NOH, thereby improving orthostatic blood pressure and alleviating associated symptoms of lightheadedness, dizziness, blurred vision, and syncope through the induction of tachycardia (increased heart rate) and hypertension.

Toxicity

Droxidopa has minimal toxic effects and an acute, oral LD50 of more than 5 g/kg in mice, rats, dogs, and monkeys. Side effects occur in in 0.78% of patients and include nausea, headache, increased blood pressure, hallucination, and anorexia.

Affected Organisms

Biotransformation

Droxidopa is metabolized by aromatic L-amino acid decarboxylase.

Absorption

Oral bioavailability is 90%.

Half Life

2-3 hours.

Elimination

Droxidopa is mainly excreted in the urine, with the main metabolite being 3-O-methyldihydroxyphenylserine.

References

External Links