Gas chromatographic-negative-ion chemical ionization mass spectrometric determination of a new dihydropyridine calcium antagonist (MPC-1304) and its metabolites in human plasma and urine

Determination of aranidipine and its active metabolite in human plasma by liquid chromatography/negative electrospray ionization tandem mass spectrometry

A simple, sensitive and rapid high-performance liquid chromatography/negative electrospray ionization tandem mass spectrometry method was developed and validated for the assay of aranidipine (AR) and its active metabolite (AR-M) in human plasma. Following a liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase column and analyzed by mass spectrometry in the multiple reaction monitoring mode using the respective [M-H]- ions, m/z 387.0 --> 164.0 for AR, m/z 389.1 --> 208.1 for AR-M and m/z 359.0 --> 121.8 for the internal standard. The assay exhibited a linear dynamic range of 0.02-10 ng x mL(-1) for AR and 0.2-100 ng x mL(-1) for AR-M in human plasma. The limits of quantitation were 0.02 ng x mL(-1) for AR and 0.2 ng x mL(-1) for AR-M. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.8 min for each sample exhibited its high-throughout analysis ability. The validated method can be applied to analyze human plasma samples for pharmacokinetic studies.

Sensitive and specific liquid chromatographic-tandem mass spectrometric assay for barnidipine in human plasma

A sensitive and specific LC-MS-MS assay has been developed and validated for barnidipine (1-benzyl-3-pyrrolidinyl)methyl-2,6-dimethyl-4(m-nitrophenyl)-1,4-dihydr opyridine-3,5-dicarboxylate). The assay involves a simple and rapid solid-phase extraction procedure. Sample analysis was on a Spherisorb S3ODS2 100 mmX2 mm I.D. column, with a Finnigan TSQ 7000 mass spectrometer, using an electrospray interface and selective reaction monitoring (SRM). The intra- and inter-day precision and accuracy, determined as the coefficient of variation and relative error, respectively, were 11.8% or less. The limit of quantitation was 0.03 ng/ml, and the calibration was linear between 0.03 and 3.0 ng/ml. The method has been used successfully for the measurement of over two thousand human plasma samples from pharmacokinetic clinical trials.

Determination of benidipine hydrochloride in human plasma by capillary column gas chromatography-negative ion chemical ionization mass spectrometry

A highly sensitive and specific determination method of a new calcium antagonist, benidipine hydrochloride, in human plasma has been developed using capillary column gas chromatography with negative ion chemical ionization mass spectrometry. A deuterated analogue of benidipine hydrochloride was used as an internal standard. Benidipine hydrochloride was extracted from plasma with diethyl ether under basic conditions, back-extracted with 0.5 M sulphuric acid, and reextracted with diethyl ether under basic conditions. For gas chromatography, a solventless injection port was used, and the whole extract was injected. Fragment ions at m/z 488 (benidipine) and m/z 493 (internal standard) were used as monitoring ions for selected-ion monitoring. The detection limit was 0.02 ng/ml with 0.5 ml of plasma. The coefficient of variation of intra-day assay was 17.4% and 12.1% at the 0.02 and 0.1 ng/ml levels, respectively. This method has made it possible to detect the plasma level of unchanged drug up to 12 h after an 8-mg oral dose of benidipine hydrochloride to humans.

Effects of MPC-1304, a novel Ca2+ entry blocker, on alpha-adrenoceptor-mediated pressor responses in pithed rats

MPC-1304 is a novel Ca2+ entry blocker of the 1,4-dihydropyridine type. In the present study, the effect of oral administration of MPC-1304 on alpha-adrenoceptor-mediated pressor responses was examined in pithed rats and compared with that of nifedipine. Drugs were administered orally to conscious animals before pithing. MPC-1304 (0.3-3 mg/kg) and nifedipine (1-10 mg/kg) inhibited pressor responses to norepinephrine, phenylephrine (alpha 1-adrenoceptor agonist), UK-14304 (alpha 2-adrenoceptor agonist), and sympathetic nerve (spinal cord segments) stimulation. MPC-1304 was roughly 3 times more potent than nifedipine in inhibiting these responses. The inhibitory effect of MPC-1304 (3 mg/kg) on the pressor response to UK-14304 lasted longer than that of nifedipine (3 mg/kg). At the same time, plasma concentrations of MPC-1304 were lower than those of nifedipine. These results suggest that MPC-1304 has a great ability to inhibit pressor responses to norepinephrine and peripheral sympathetic stimulation after its oral administration, and that this effect of MPC-1304 is closely correlated with its potent antihypertensive activity.

Calcium entry blocking activities of MPC-1304 and of its enantiomers and metabolites

The Ca2+ entry blocking effects of MPC-1304, a new Ca2+ entry blocker of the 1,4-dihydropyridine type, and of its (S) and (R) enantiomers and metabolites were examined on Ca(2+)-induced contractions in isolated rabbit arteries. The Ca2+ entry blocking activity of the (S) enantiomer of MPC-1304 was approximately 150 times greater than that of its (R) enantiomer. Likewise, the antihypertensive effect of the (S) enantiomer was twice as great as that of MPC-1304 (racemate) in conscious spontaneously hypertensive rats, while the (R) enantiomer was ineffective. Thus, most of the pharmacological activity of MPC-1304 resides in its (S) configuration. The main metabolic products of MPC-1304 also inhibited the Ca(2+)-induced contraction in the isolated vascular smooth muscles. These active metabolites showed a stereoselectivity similar to that of MPC-1304 for Ca2+ entry blocking activity, and may contribute to the potent antihypertensive action of MPC-1304.

Determination of a new calcium antagonist and its main metabolite in plasma by thermospray liquid chromatography-mass spectrometry

A highly sensitive thermospray liquid chromatographic-mass spectrometric method has been developed for the simultaneous determination of FRC-8653 (I), a new calcium antagonist, and its main metabolite (M-4) in plasma. A deuterated analogue of I was added to the plasma as the internal standard. After the purification and concentration of the plasma sample on bonded-phase disposable columns, the extract was injected into the thermospray liquid chromatograph and analysed by selected-ion monitoring mass spectrometry. The calibration curves obtained were linear over the concentration range 0.5-100 ng/ml. The limits of quantification are 0.5 ng/ml for I and 1 ng/ml for M-4 in plasma, which are sufficient to evaluate plasma concentrations after oral administration to rats.

Use of a carrier for quantitation of a new dihydropyridine calcium antagonist (OPC-13340) in human plasma by highly sensitive gas chromatography with negative-ion chemical ionization mass spectrometry

A sensitive gas chromatographic-mass spectrometric method for the quantitation of (+/-)-methyl 3-phenyl-2(E)-propenyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate (OPC-13340, I), a new dihydropyridine calcium antagonist with a potent and long-acting antihypertensive and antianginal effect, was developed in order to elucidate its pharmacokinetics. Dihydropyridine calcium antagonist have been usually quantifed by this technique in the negative-ion chemical ionization mode. However, direct application of this method to quantify trace amounts of I in biological fluids completely failed, owing to its adsorption on the column and oxidation of its dihydropyridine ring. Human plasma containing I and (+/-)-[2H3]methyl 3-phenyl-2(E)-propenyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate (II), the internal standard, was extracted with n-hexane-diethyl ether under weakly basic conditions (pH 8). In order to prevent adsorption of the compounds on the column, (+/-)-[2H5]ethyl 3-phenyl-2(E)-propenyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate (III), an analogue of I, was added to the extracts as a carrier. In addition, this carrier was also effective in preventing the oxidation of I. The quantitation limit of I in human plasma by this method was found to be less than 30 pg/ml. Thus, the method is sufficiently sensitive to study the pharmacokinetics of I in humans.

Simultaneous determination of a new dihydropyridine calcium antagonist (MPC-1304) and its metabolite in dog plasma by high-performance liquid chromatography with electrochemical detection

A rapid and sensitive high-performance liquid chromatographic analysis, with electrochemical detection, has been developed for the simultaneous determination of a new calcium-channel antagonist, (+/-)-methyl 2-oxopropyl-1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinedi carboxylate (I, MPC-1304), and its active metabolite in dog plasma. The plasma extract with toluene was chromatographed on a reversed-phase column and detected by an electrochemical detector at + 0.92 V. Calibration curves were linear from 2.0 to 100.0 ng/ml, and the detection limit was ca. 0.25 ng/ml. This method is applicable to the simultaneous determination of I and its metabolite in dog plasma following the oral administration of I.

Chromatography of calcium channel blockers

Numerous publications during the past ten years have described the determination of various calcium channel blockers in biological fluids, using gas and liquid chromatographic techniques. Diltiazem, verapamil, flunarizine and a growing number of dihydropyridines belong to this group of drugs, which in most instances are active at low plasma concentrations. From a bioanalytical point of view these compounds have many features in common, such as high lipophilicity and favourable detection properties.