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.

mechanism of action

Droxidopa crosses the blood-brain barrier where it is converted to norepinephrine via decarboxylation by L-aromatic-amino-acid decarboxylase. Increased levels of norepinephrine in the central nervous system (CNS) may be beneficial to patients in a wide range of indications. Norephinephrine acts at alpha-adrenergic receptors as a vasoconstrictor and at beta-adrenergic receptors as a heart stimulator and artery dilator.

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.

biotransformation

Droxidopa is metabolized by aromatic L-amino acid decarboxylase.

absorption

Oral bioavailability is 90%.

half life

2-3 hours.

route of elimination

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