Eiichi Mafune

Determination of timiperone in rat plasma by high-performance liquid chromatography with electrochemical detection

We report a sensitive new method for the determination of timiperone in rat plasma by using high-performance liquid chromatography with electrochemical detection. The method involves extraction of plasma samples with heptane-isoamyl alcohol at pH > 8, followed by back-extraction into dilute acetic acid. Separation was accomplished by reversed-phase high-performance liquid chromatography on an ODS column with the mobile phase consisting of 0.1 M phosphate buffer (pH 3.5)-acetonitrile-methanol (65:20:15, v/v). Recovery was greater than 80%. Calibration curve was linear over the concentration range 0.5-50.0 ng/ml. The limit of quantitation of timiperone was 0.5 ng/ml plasma.

Pharmacological activities of timiperone transdermal dosage forms composed of water-soluble polymer matrix in rats.

To prevent the emesis associated with anticancer therapy with chemotherapeutic drugs, various investigations have been conducted into transdermal dosage forms containing timiperone, antipsychotics and strong antiemetics. In the present study, we used the water-soluble polymers as a matrix for transdermal dosage forms. Further, we also evaluated the effect of matrix pH on the inhibition action of timiperone on apomorphine-induced stereotyped behavior in an in vivo model in rats, and compared pharmacological activity with these water-soluble matrices to that obtained with a plaster formulation. Inhibition of timiperone on apomorphine-induced stereotyped behavior was used as an index of percutaneous absorption of timiperone. Results showed that pharmacological activity increased with increasing matrix pH. This finding suggests that the percutaneous absorption of timiperone is pH-dependent. At 4 h after the administration of water-soluble polymer matrices, the pharmacological activity of timiperone was closely similar to that at the same time-point after oral administration of the drugs. Further, this activity was maintained for up to about 8 h after administration. These findings suggest that the transdermal dos age form of timiperone prepared from these water-soluble polymers is effective and longer-acting preparations to prevent the emesis associated with anticancer therapy with chemotherapeutic drugs.

Preliminary Preformulation Studies of a 2-(3,4-Dimethoxyphenyl)ethylamine Derivative for Oral Administration at an Exploratory Stage of New Drug Development.

Preliminary preformulation studies of a 2-(3,4-dimethoxyphenyl)ethylamine derivative were investigated. The hydrochloride form showed incompatibility with the excipients used for oral dosage forms. There were several crystal forms of the free base, namely, alpha-anhydrate, beta-anhydrate, monohydrate, and trihydrate. The trihydrate form was unstable. The degree of crystallinity of the beta-anhydrate form was difficult to control. The monohydrate form was difficult to manufacture with constant quality. The serum levels of the compounds in rats were almost related to the dissolution rates in the JP 1st disintegration medium from the discs. The serum level of alpha-anhydrate was the lowest. However, the dissolution rates from the formulations of alpha-anhydrate were improved. After oral administration of the improved formulation, the serum level of alpha-anhydrate in beagle dogs was almost triple that after the oral administration of the capsule of the hydrochloride form.

Determination of malotilate and its metabolites in plasma and urine

A method for the determination of malotilate (I), the corresponding monocarboxylic acid (II) and its decarboxylated product (III) in plasma is described. Plasma was extracted with chloroform spiked with internal standard. The residue, dissolved in methanol, was chromatographed on a reversed-phase column with a mobile phase of 60% acetonitrile and 1% acetic acid in water. The sensitivity limit for I, II and III was 50, 25 and 100 ng/ml of plasma, respectively. Compound I in the same plasma extract was also analysed by gas chromatography--electron-impact mass spectrometry. The base peaks m/z 160 for I and m/z 162 for internal standard (IV) were monitored; the sensitivity limit for I was 2.5 ng/ml of plasma. The determination of the metabolites of I, II and its conjugate (V), and isopropyl-hydrogen malonate (VI) in urine by high-performance liquid chromatography is also described. The limit of quantification for VI was 2.0 micrograms/ml, and the overall coefficient of variation of VI was 4.7%. The limit of quantification for II in urine was 0.5 micrograms/ml and that for V was 1.0 micrograms/ml as total II (II + V). The overall precision of the method was satisfactory. The method was used to determine plasma and urine concentrations in four dogs orally dosed with 100, 200 or 400 mg of malotilate.