生物活性

• 描述Levodopa is an orally active metabolic precursor of neurotransmitters dopamine. Levodopa can cross the blood-brain barrier and is converted into dopamine in the brain. Levodopa has anti-allodynic effects and the potential for Parkinson's disease^[3]. Levodopa is the most effective anti-Parkinsonian agent. For the levodopa groups (10-100 mg/kg), tactile and heat withdrawal thresholds were increased, and cold withdrawal frequency was decreased dose-dependently. In addition, levodopa induced biphasic analgesia. Different dosage of levodopa did not impact on the rotarod time^[4]. Levodopa is available in three forms: immediate-release, orally disintegrating and sustained-release tablets. Results of current levodopa trials suggest that treatment with levodopa at the onset of disease provides superior motor and functional control compared with dopamine receptor agonists. Moreover, levodopa is generally better tolerated with a lower incidence of gastrointestinal and neuropsychiatric adverse effects. In young parkinsonian patients with mild motor dysfunction, use of levodopa may be delayed or the dosage minimised. In older PD patients with lesser risk of motor fluctuations, levodopa may be used initially, and perhaps solely, in demented PD patients and those at higher risk of developing neuropsychiatric adverse effects^[5]. Strategies currently being used to achieve more continuous dopaminergic stimulation include the combination of an oral levodopa/DDC (dopa decarboxylase) inhibitor with a COMT (catechol-O-methyltransferase) inhibitor and the enteral infusion of a levodopa gel formulation^[6].