Akikazu Nomura

Evaluation of pH-independent sustained-release granules of dipyridamole by using gastric-acidity-controlled rabbits and human subjects

The solubility of dipyridamole at pH 2.5 was about 6000-fold greater than that at pH 7.0. A commercial powder of dipyridamole showed pH-dependent dissolution. Two kinds of sustained-release granules of dipyridamole were prepared. The release rate of pH-dependent sustained-release granules was controlled by ethylcellulose (EC) and decreased with increasing medium pH. The release rate of pH-independent sustained-release granules was regulated by carboxymethylethylcellulose (CMEC), hydroxypropyl methylcellulose (TC-5) and Eudragit RS100, and was not influenced by varying pH of the medium. We used gastric-acidity-controlled rabbits to evaluate the variability in absorption after oral administration of these formulations. An extremely large difference in bioavailability between the high and low gastric acidity groups was observed after oral administration of the commercial powder. There were no statistically significant differences in the values of Cmax, Tmax, AUC0–12h and MRT between the high and low gastric acidity groups after administration of pH-independent sustained-release granules, while statistically significant differences in Cmax and AUC0–12 h were found between the two groups after administration of pH-dependent sustained-release granules. Furthermore, this pH-independent sustained-release granule preparation was administered orally to human subjects and compared with the commercial powder. There was no significant difference in the AUC0–12 h between the two preparations. It was also shown that the Cmax for the granules was about 50% of that for the commercial powder and that the plasma levels after oral administration of the granules were maintained over a longer duration than those of the commercial powder. It was found that the bioavailability was not influenced by variations in gastric acidity in rabbits and high bioavailability was achieved in human subjects after oral administration of the pH-independent sustained-release granule preparation, indicating that this preparation should be a useful dosage form for the potential reduction of interindividual variabilities in absorption.

Acute and chronic effects of verapamil in patients with paroxysmal supraventricular tachycardia.

Efficacy of acute intravenous verapamil, 10 mg, and chronic oral verapamil, 320 mg, daily were studied electrophysiologically in 15 patients with paroxysmal supraventricular tachycardia (PSVT). Plasma verapamil concentrations were measured concurrently. Both intravenous and oral verapamil significantly increased the AV node conduction time, the cycle length producing a Wenckebach period, and the refractory period of the AV node. These changes were reflected in changes in plasma verapamil concentration. The echo zone and the supraventricular tachycardia (SVT) zone markedly narrowed after administration of both intravenous and chronic oral verapamil. Verapamils efficacy was found to be related to the type of SVT. For instance, verapamil was more effective in SVT due to AV nodal re-entry than in SVT due to concealed accessory pathway. Fourteen patients were followed from 3 to 31 months and all except one were well controlled. In conclusion, verapamil was effective in prophylaxis of paroxysmal SVT.

Alpha‐1‐Acid Glycoprotein Concentration and the Protein Binding of Disopyramide in Healthy Subjects

Age‐ and gender‐related changes in serum α1‐acid glycoprotein (AAG) concentration and the serum protein binding of disopyramide were examined after intensive medical examination. Based on the clinical chemistry tests over 51 points, 245 subjects were diagnosed as healthy and 71 subjects (22.5%) revealed an abnormal value for at least one item. In the healthy subjects, serum AAG concentration in men was significantly higher than in women (men, 0.78 ± 0.18 mg/mL, mean ± SD; women, 0.67 ± 0.16 mg/mL). In contrast, there were no significant differences in the AAG concentration between age groups for men and women and in the unbound fraction of disopyramide. Gender changes AAG concentration. Age, however, does not change AAG concentration and the protein binding of the basic drug.

Effect of furosemide in congestive heart failure

The diuretic effect of furosemide was studied in 18 patients with congestive heart failure. Subjects were divided into two groups, group I consisting of eight patients with moderate and group II of 10 patients with advanced congestive heart failure. Six hours after bolus injection of furosemide (40 mg), mean urinary sodium was 120.5 ± 36.7 mEq in group I and 68.2 ± 25.8 mEq in group II (p < 0.01), mean urine volume was 1,100 ± 281 and 764 ± 257 ml (p < 0.05), mean urinary furosemide excretion was 28.08 ± 2.60 and 24.00 ± 0.74 mg (p < 0.05), and mean furosemide renal clearance was 73.4 ± 16.6 and 42.3 ± 11.5 ml/min (p < 0.001). Diuretic effect and furosemide renal clearance, as well as urinary furosemide excretion, correlated positively. The diuretic effect of furosemide with and without hydralazine (0.2 mg/kg) was compared in eight patients in group II. Urinary sodium excretion 6 hr after furosemide rose from 77.2 ± 31.0 to 122.8 ± 42.5 mEq after furosemide with hydrlazine (p < 0.01). Urine volume rose from 854 ± 278 to 1,279 ± 359 ml (p < 0.001), urinary furosemide excretion rose from 23.64 ± 2.03 to 26.94 ± 2.30 mg (p < 0.01), and furosemide renal clearance rose from 46.3 ± 12.2 to 62.5 ± 18.6 ml/min (p <0.01).

Single-step isolation method for six glycoforms of human α1-acid glycoprotein by hydroxylapatite chromatography and study of their binding capacities for disopyramide

A single-step isolation method for the glycoforms of human serum alpha1-acid glycoprotein (AAG) using a hydroxylapatite column under a gradient elution program was developed. The concentrations of N-acetylneuraminic acid and monosaccharides (fucose, N-acetylglucosamine, galactose and mannose) of six AAG glycoforms were determined by the pulsedamperometric detection method. For each AAG glycoform, significant sex-related differences in carbohydrate content have been observed only for AAG glycoforms two and six, and not for each AAG glycoform. The relationship between the extent of the branch in the glycan chain and the binding capacity to disopyramide were examined. Female AAG contained highly sialylated AAG glycoforms compared to male glycoforms. Conversely, male AAG was rich in the lower sialylated AAG glycoform. Furthermore, it was found that the drug binding capacity decreases with increasing branching of the glycan chain. This suggests that the binding sites of AAG are hindered by a relatively large carbohydrate moiety, such as tetraantennary structures.

Recovery of cardiac norepinephrine concentration and tyrosine hydroxylase activity by the central α2-adrenoceptor agonist guanabenz in rats with aortic constriction

Depletion of cardiac norepinephrine has been reported in cardiac hypertrophy. This depletion causes less support for cardiac output in response to sympathetic nerve activation. The central nervous system is thought to be involved in this abnormality. Correction of this abnormality is expected to restore proper support for the heart. Clipping of the ascending aorta or a sham operation was performed in 10-week-old rats. At 4 weeks after the operation, the left ventricular norepinephrine concentration in clipped rats decreased (p<0.01). The clipped rats and sham-operated rats were treated with either guanabenz (1 mg/kg) or a vehicle for 4 weeks starting from fifth postoperative week. The level of left ventricular norepinephrine increased more in clipped rats treated with guanabenz (469+/-37 ng/g) than in clipped rats treated with a vehicle (325+/-28 ng/g). The norepinephrine concentration in the left ventricle recovered significantly after the treatment with guanabenz (p<0.001). Tyrosine hydroxylase activity in the left ventricle also recovered after treatment with guanabenz (p<0.01). Modulation of sympathetic nerve tone by the alpha2-adrenoceptor agonist restored cardiac norepinephrine concentration and tyrosine hydroxylase activity. This could be a new approach to the treatment of heart failure.

Changes in the binding capacity of alpha-1-acid glycoprotein in patients with renal insufficiency.

Summary The elevation of alpha-1-acid glycoprotein (AAG) concentration and the binding characteristics of disopyramide (DP) to AAG in patients with renal insufficiency were investigated. The serum AAG concentration and protein binding of DP in patients were significantly greater than those in healthy subjects. However, in both the serum and the purified AAG, Scatchard analysis showed that the number of binding sites per molecule of AAG in patients was significantly lower than that in healthy subjects, although there was no difference in the dissociation constant (Kd). These results suggest that the AAG induced in renal insufficiency is qualitatively different from normal AAG. Moreover, the change of the unbound DP fraction when DP concentration was increased was larger in the patients than in the healthy controls. Therefore, monitoring of the unbound DP would be important for therapeutic drug monitoring in patients with renal insufficiency.

Purification method for α-1-acid glycoprotein with subsequent high-performance liquid chromatographic determination of monosaccharides in plasma of healthy subjects and patients with renal insufficiency

A simple purification method for human plasma α-1-acid glycoprotein (AAG) using an ion-exchange and hydroxyapatite column was developed. The recovery of the method was found to be high. We also improved a determination method for N-acetylneuraminic acid and monosaccharides in the carbohydrate moiety of AAG by using an ion-exchange column and pulse-amperometric detection. By this method, a composition analysis of the carbohydrate moiety of AAG (N-acetylneuraminic acid, fucose, N-acetyl glucosamine, galactose and mannose) was possible with 1.0 ml of plasma. We compared these carbohydrate concentrations in the AAG of patients with renal insufficiency with those of healthy subjects. In the AAG of the patients, the concentrations of N-acetylglucosamine, galactose and mannose were significantly higher than those in the AAG of the healthy subjects.

Hydralazine and furosemide kinetics

Furosemide kinetics were studied in 25 patients with congestive heart failure. The elimination half‐life (t½) was longer and the elimination rate constant and the plasma clearance smaller in patients with advanced (n = 15) than in those with moderate (n = 10) failure. Furosemide kinetics with and without hydralazine were compared in eight patients with advanced heart failure. Furosemide t½ in patients receiving both drugs fell from 96 ± 16 to 81 ± 15 min (P < 0.02), elimination rate constant increased from 0.0186 ± 0.0056 to 0.0214 ± 0.0068 min−1 (P < 0.05), and plasma clearance rose from 72.6 ± 18.5 to 88.1 ± 26.9 ml/min (P < 0.01). Renal clearance rose from 45.4 ± 12.0 to 60.9 ± 19.0 ml/min (P < 0.01) and creatinine clearance was unchanged. We conclude that hydralazine affects furosemide kinetics.

Malignant Cardiac Pheochromocytoma With Bone Metastases

A 25-year-old man was referred to our hospital because of an abnormal shadow in the mediastinum, detected by gallium scintigraphy, and bone fractures. Three weeks before admission, he experienced severe neck pain while practicing golf at a driving range. The next morning, he was brought to a neurosurgeon by ambulance because the pain had become more severe and he was beginning to lose consciousness. A cervical radiograph showed a C4 compression fracture, and 99mTc bone scintigraphy depicted abnormal shadows in the left frontal bone, C2, C4, Th10, and right 8 rib. Gallium scintigraphy suggested a tumor in the mediastinum (Fig 1⇓). Physical findings at admission, including blood pressure of 110/62 mm Hg, were within …