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• Anti-Parkinson's disease drugs

  Entacapone is an anti-Parkinson's disease drug which is successfully developed by Orion Pharma company in Swedish. It is a highly selective potent catechol-O-methyltransferase (COMT) inhibitor, rarely penetrating the blood-brain barrier, and primarily acting in the intestinal tract. It is dose-dependent to decrease levels of 3-OMD in serum and the brain, increasing levodopa, dopamine and DOPAC levels in the brain and significantly reducing the dose which is required to increase dopamine concentration in striatal. Levodopa and carbidopa combining with COMTI can significantly increase the bioavailability of levodopa (3-4 times). Activity of COMTI in red blood cell is reversible. When in 800mg dose, the maximum inhibitory activity is up to 82%, so Entacapone combines with levodopa and carbidopa, which can be used for adjuvant therapy of idiopathic Parkinson's disease.;

• Pharmacokinetics

  This product is rapid oral absorption, the bioavailability is a dose-dependent with the range of 30% to 45%. In the range of 5~800 mg, pharmacokinetics of Entacapone (abbreviation: Ent) is linear, peak plasma concentration is related to AUC and dose. Food does not affect the absorption of this product, 98% Ent combines with plasma albumin, rarely distributing in tissues. In patients with Parkinson disease (abbreviated: PD), and is required to take levodopa/carbidopa, the peak concentration of Ent arrives within 1~2h. The rate of Ent through the blood-brain barrier is low, the plasma elimination half-life is 1.5~3.5h. After oral administration, Ent (E-configuration) is metabolized to Z-isomer in the blood and is present in plasma and red blood cells. Z-isomer has little impact on the clinical efficacy. Its drug-time curve is similar to Ent. Z-Ent accounts for about 5% of the total AUC. Ent and Z-Ent are acidified by glucose in the liver. After metabolism of Ent: 10% excreted in the urine, 90% of Ent excreted in the feces, only 0.2% excreted in the urine in phony drugs. While taking levodopa in PD patients, and oral Ent 200 mg after elimination half-life of about 1 h, the body has no savings.
  Pharmacokinetic study shows that in healthy persons and patients with PD, Ent can increase the bioavailability of levodopa. In the short-term PD patients taking Ent, AUC of levodopa increase 25%, while the long-term taking Ent can increase 50%. AUC of 3-OMD relatively reduces 60%. In these studies, they found that plasma peak time of levodopa will be extended. Single dose of Entacapone (while not taking levodopa/carbidopa), in patients with liver disease, the patient's AUC and Cmax is 2 times of the patients with normal liver function. We should adjust the dosage of the patient. In patients with mild to moderate kidney disease, it is not necessary to adjust the dosage. Kidney patients receiving dialysis can extend dosing interval.
  The above information is edited by the Chemicalbook of Liu Yujie.;

• Chemical property

  Crystals, melting point 162--163 ℃.;

• Uses

  As COMT inhibitors, it is used to treat Parkinson's disease.;

• Production method

  1.83 g 3,4-dihydroxy-5-nitrobenzaldehyde and 1.5g N, N-diethyl-cyanoacetamide and a catalytic amount of piperidine acetate are dissolved in 40ml of dry ethanol , followed by stirring overnight , 2.23 g crude product is obtained, yield 73%, melting point 153~156 ℃.
  Heated at 90 ℃, the 3.0 kg crude product is dissolved in 8.0kg acetic acid (or formic acid) containing 80 g HBr (or 40gHCl).It is slowly cooled to 20 ℃, and stirred at this temperature for 20h, then at 15 ℃ stirred for 6h. The precipitated crystals were collected by filtration, carefully washed with cool (4 ℃) 1L toluene-acetic acid (1: l v/v) mixed solution, and washed with 1L cold toluene. It is dried at 45 ℃under vacuum and 2.4kg crystalline pure Entacapone is obtained, yield 80%, melting point 162-163 ℃.;

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