Pharmacokinetics and pharmacodynamics of (+/-)-sotalol in healthy male volunteers

1. We investigated the pharmacokinetics and pharmacodynamics of (+/-)-sotalol administered orally to healthy male volunteers in single doses of 40, 80 and 160 mg and in multiple doses of 80 mg twice daily for 7 consecutive days. 2. In the single dose studies, the half-life of (-)-sotalol (7.2-8.5 h) was significantly (P < 0.01) shorter than that of (+)-sotalol (9.1-11.4 h) while the renal clearance of (-)-sotalol (110.6-126.4 ml min-1) was significantly (P < 0.01) faster than that of (+)-sotalol (102.2-110.1 ml min-1). In the multiple dose studies, similar differences in the pharmacokinetics of (+)- and (-)-sotalol were observed. In addition, the pharmacokinetics of both (+)- and (-)-sotalol on day 4 were shown to be essentially the same as those on day 7. 3. In pharmacodynamic examinations, (+/-)-sotalol prolonged QTc intervals on electrocardiograms dose-dependently after single doses of 80 and 160 mg (3.81 +/- 2.96%, 13.23 +/- 5.66%). The correlation between the plasma concentration of (+/-)-sotalol and prolongation of QTc intervals was nearly linear, and showed no hysteresis. 4. In conclusion, we demonstrated that QTc interval was prolonged with a linear correlation to the plasma concentration of (+/-)-sotalol. In addition, our study suggested that differences in the pharmacokinetics of (+)- and (-)-sotalol may be attributable to faster urinary excretion of (-)-sotalol.

Difference in CDDP penetration into CSF between selective intraarterial chemotherapy in patients with malignant glioma and intravenous or intracarotid administration in patients with metastatic brain tumor

Platinum (Pt) levels in plasma and cerebrospinal fluid (CSF) in patients with malignant glioma were determined after initiation of selective intraarterial chemotherapy with a combination of VP-16 (etoposide) and CDDP (cisplatin), and were compared with the CSF Pt levels in patients with metastatic brain tumors after intravenous or intracarotid administration of VP-16 and CDDP. CSF Pt levels were also compared for various administration routes, doses, CSF sampling routes and blood-CSF barriers in metastatic brain tumor. Changes in the blood-CSF barrier to CDDP during treatment in a patient with meningeal lymphoma and in a patient recovering from surgical removal of a metastatic brain tumor were also examined by periodic administration of CDDP. All CSF samples were taken through Ommaya reserviors placed in the anterior horn of the lateral ventricle or the postoperative cavity. The mean peak CSF/plasma total Pt ratio (T/T ratio) and the mean CSF total Pt/plasma ultrafiltrable Pt ratio (T/U ratio) were highest (15.0% and 24.4%, respectively) following selective intraarterial infusion of CDDP in patients with malignant glioma, followed by intravenous infusion in meningeal carcinomatosis (11.5% and 18.9%), intracarotid administration (5.4% and 8.7%) and intravenous infusion (60 mg/m2 2.5% and 100 mg/m2 2.9%; and 60 mg/m2 3.5% and 100 mg/m2 7.7%) in patients with the solid type of metastatic brain tumor. In CSF obtained from the postoperative cavity in cases of metastatic brain tumor, T/T and T/U ratios were extremely high (40.9% and 62.4%). However, the CSF Pt level even after selective intraarterial administration of CDDP in malignant glioma was 0.51-1.64 micrograms/ml total Pt and 0.43-1.08 micrograms/ml ultrafiltrable Pt. Even the CSF level obtained from the postoperative cavity was 1.0-4.7 micrograms/ml total Pt. These low levels of total and ultrafiltrable Pt are considered not to be cytotoxic to disseminated cells in the CSF space and to normal brain cells. As for changes in the blood-CSF barrier, repeated administration of CDDP showed that the rate of entry of Pt into the CSF decreased in parallel with improvements apparent on CT scans in the patient with meningeal lymphoma, and also showed that the blood-CSF barrier to Pt was gradually repaired after the metastatic brain tumor had been removed.

Enantioselective determination of sotalol enantiomers in biological fluids using high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatographic (HPLC) method for the determination of (+)-(S)-sotalol and (-)-(R)-sotalol in biological fluids was established. Following extraction with isopropyl alcohol from biological samples on a Sep-Pak C18 cartridge, the eluent was derivatized with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate (GITC). The diastereoisomeric derivates were resolved by HPLC with UV detection at 225 nm. Calibration was linear from 0.022 to 4.41 micrograms/ml in human plasma and from 0.22 to 88.2 micrograms/ml in human urine for both (+)-(S)- and (-)-(R)-sotalol. The lower limit of determination was 0.022 microgram/ml for plasma and 0.22 microgram/ml for urine. The within-day and day-to-day coefficients of variation were less than 7.5% for each enantiomer at 0.09 and 1.8 microgram/ml in plasma and at 0.44 and 4.4 micrograms/ml in urine. The method is also applicable to other biological specimens such as rat, mouse and rabbit plasma.

Clinical pharmacokinetics and pharmacodynamics of paclitaxel: a 3-hour infusion versus a 24-hour infusion

The present study was conducted to compare the pharmacokinetics and pharmacodynamics (PD) of paclitaxel between Phase I trials of 3- and 24-h infusions and to determine the most informative pharmacokinetic parameter to describe the PD. Twenty-seven patients were treated in a Phase I study of paclitaxel by a 3-h infusion at one of six doses: 105, 135, 180, 210, 240, and 270 mg/m2. Pharmacokinetic data were obtained from all patients. Paclitaxel concentrations were measured in the plasma and urine using HPLC. The pharmacokinetics and PD were compared with those of a Phase I trial of paclitaxel by a 24-h schedule previously performed. The maximum tolerated dose of paclitaxel by a 3-h infusion was determined to be 240 mg/m2. The major toxicities were granulocytopenia, neuromuscular toxicities, and hypotension. Apparent differences in pharmacodynamic relationships for the change in granulocytes with dose, peak concentration, and areas under the concentration versus time curve were observed between the 3- and 24-h schedules. However, the relationship between the duration of plasma concentration above 0.05 microM and the change in granulocytes could be fitted to the same sigmoid maximum effect model in either schedule (P < 0.01). There were no clear relationships between peripheral neuropathy or hypotension and any pharmacokinetic parameters. The pharmacokinetics and PD of paclitaxel were schedule dependent. The duration of plasma concentration above 0.05 microM could be a common pharmacokinetic parameter predicting granulocytopenia for both schedules.

[Determination of new anticancer drug, paclitaxel, in biological fluids by high performance liquid chromatography]

A simple and reproducible high performance liquid chromatographic (HPLC) method using an internal standard (I.S.) was developed for the determination of an anticancer drug, paclitaxel, in biological fluids. The sample preparation involves a solid-phase extraction step. HPLC was performed on an ODS column using acetonitrile-2 mM phosphoric acid (45:55) as a mobile phase with detection at 227 nm. A linear relationship was obtained in the range of 0.02-2.0 micrograms/ml in the rat plasma and urine. Since the recovery of the drug was as high as that of I.S. (> 96%), a standard curve generated from the solution of the drug with I.S. in the mobile phase could be used for determination. The method could be applicable for human and dog plasma as well as rat plasma, and the intra- and interday coefficients of variation at 0.05, 2.0 and 10.0 micrograms/ml were less than 7%. This method is useful for pharmacokinetic studies of paclitaxel.

[Pharmacokinetics of cefprozil in infant and adult beagle dogs]

The Pharmacokinetics of cefprozil was studied upon oral administration of 25 mg/kg to fasted infant and adult Beagle dogs. When the pharmacokinetic parameters between infant and adult dogs were compared, the mean peak concentration (Cmax) in infant dogs (21.2 micrograms/ml) was significantly (P < 0.01) lower than that of adult dogs (27.8 micrograms/ml). But significant differences were not found in the areas under the concentration-time curve (AUC, in infant dogs: 121 micrograms.hr/ml, in adult dogs: 130 micrograms.hr/ml), half-lives (T 1/2, in infant dogs: 4.7 hours, in adult dogs: 4.7 hours) or urinary recovery rates (UR, in infant dogs: 36.3%, in adult dogs: 34.7%) between the 2 groups. These results suggest the distribution volumes of infant dogs are larger than those of adult dogs, and the absorption rates of infant dogs are slower than those of adult dogs, whereas the absorption quantities are similar.

[Study on the pharmacokinetics of cefepime (I)]

The pharmacokinetics of 14C-cefepime dihydrochloride (14C-CFPM), were studied in rats upon both single and repeated intravenous administration. 1. Blood level of radioactivity was 59.27 micrograms eq./ml at 5 minutes after single intravenous administration at a dose of 20 mg/kg, and declined biexponentially thereafter. The values of AUC and T 1/2 were 70.1 micrograms eq..hr/ml and 38.0 hours, respectively. 2. Blood level of radioactivity was 59.41 micrograms eq./ml at 5 minutes after administration on the 7th day of repeated intravenous administration at a daily dose of 20 mg/kg, and declined more slowly as compared to the case of single administration. The values of AUC and T 1/2 after repeated administration were 159.7 micrograms eq..hr/ml and 44.5 hours, respectively. 3. Urinary and fecal excretion rates after single administration were 93.3% and 3.3%, respectively. 4. Urinary and fecal excretion rates were almost constant throughout the repeated administration; 88.4-90.7% and 2.3-3.7%, respectively. 5. 14C-CFPM distributed rapidly to the whole body except to the central nervous system. Although the radioactivity was removed rapidly from tissues, high levels of radioactivity remained in the kidney and the spleen as compared to other tissues. 6. Tissue concentrations of radioactivity at 5 minutes after the final dose of repeated administration were about the same as those after single administration but they declined more slowly than those after single administration. High levels of radioactivity were found in the kidney and the spleen as were found upon single administration. The ratios of these levels between repeated and single dosing were 4.3 and 2.6 for kidney and spleen, respectively. 7. Data obtained with autoradiograms of the whole body were consistent with measured tissue distribution obtained in both cases of single and repeated administration.

[Study on the pharmacokinetics of cefepime (II)]

The pharmacokinetics of 14C-cefepime dihydrochloride (14C-CFPM), was studied in dogs after single intravenous administration at a dose of 20 mg/kg. Protein binding was also investigated both in vitro and in vivo. 1. Blood level of radioactivity was 83.53 microns eq./ml at 5 minutes after single intravenous administration and declined biexponentially thereafter. The values of AUC and T1/2 were 229 microns eq.(.)hr/ml and 90 hours, respectively. 2. Urinary and fecal excretion rates were 95.1% and 2.7%, respectively. 3. The in vitro protein binding at 1 to 100 microns/ml of drug concentration was 7.9 to 12.7% in rat, 12.4 to 18.6% in human, and 12.5 to 14.5% in dog. In vivo protein binding, which increased with time after administration, was 10.8 to 92.9% in rat and 17.5 to 64.9% in dog at 5 minutes to 6 hours.

[Pharmacokinetics of BMY-28100 in multiple administration]

A multiple dose trial of BMY-28100, a new oral cephalosporin, was performed in volunteers, in order to evaluate its safety and pharmacokinetics. BMY-28100 was administered orally 250 mg t.i.d. for 7 days to seven healthy adult males. No side effects nor abnormal laboratory findings were observed. Peak levels of serum concentration and half-lives after the first and 19th administrations were 4.45 and 4.83 micrograms/ml and 1.3 and 1.1 hours, respectively. Urinary recoveries in 24 hours were 53.4% on day 1 and 56.2% on day 7. There was no tendency towards accumulation in blood upon continuous daily dosing of 250 mg t.i.d.

[Microbiological assay method of BMY-28100 and some other cephem antibiotic in serum and tissues. Development of new sample preparation with Evan's blue, a high albumin binding dye]

With a new simple sample pretreatment, microbiological assay methods for quantitative determination of BMY-28100 and some other cephem antibiotics in serum and tissues have been developed. Presented sample pretreatment was founded on the extraction with Evans' blue, a high serum protein binding dye, and the ultrafiltration using cellulose membrane (Millipore; MW cutoff is 10,000) to which Evans' blue was specifically absorbed. Regardless of sample media, antibiotic contents in filtrates were determined accurately using calibration curves based on standard solutions prepared with 1/15 M phosphate buffer, pH 7.4. Four cephems, ceftriaxone (CTRX), cefazolin (CEZ), BMY-28100 and cefadroxil (CDX) were examined in human serum and rat liver tissues. Corrections were made for antibiotic recoveries into 1/15 M phosphate buffer, pH 7.4. CTRX, CEZ, BMY-28100 and CDX in serum and tissues were recovered into buffer at rates of 98.4-101.6%, 97.6-102.0%, 99.8-101.4% and 97.5-98.2% of of spiked (theoretical) values, respectively regardless of antibiotic concentrations. Furthermore, these concentrations obtained using the present bioassay method were well in agreement with those obtained by the HPLC method. When BMY-28100 was administered to volunteers, concentrations of BMY-28100 in serum obtained by the present bioassay method were well in agreement with those obtained by the usual bioassay method which required the fresh human serum to prepare the standard solutions.

[Studies on the pharmacokinetics of BMY-28100 (II)]

Studies were done in rats on placental transfer and excretion into milk of 14C-BMY-28100 upon single oral administration. Studies on absorption, distribution and excretion of 14C-BMY-28100 were also done upon multiple dosing. 1. Fetal tissue concentration of the drug reached a maximum at 6 hours after dosing on day 18 of gestation. The highest concentration observed was only 0.56 microgram equiv./g in fetal kidney; The transfer of radioactivity into the fetus was low. Similar results were obtained from whole body autoradiograms performed in rats on day 12 and day 18 of gestation. 2. Concentrations of radioactivity in milk reached a maximum of 0.60 microgram equiv./ml at 1 hour after administration, and gradually decreased thereafter. The maximum concentration in milk was 10% of the plasma concentration measured at the same time. 3. In the multiple oral administration study, 24 hours blood levels of radioactivity rose progressively with each dose, and reached a level 3.8 times higher than that observed with single dosing by the final (21st) administration. Tissue concentrations were relatively high in aorta, kidney and large intestine as were found upon single administration. However, the ratios of these levels between multiple and single dosing were lower than those observed in blood; 1.7, 3.6 and 2.9 for aorta, kidney and large intestine, respectively. Urinary and fecal excretion were constant after the 2nd administration.

[Studies on the pharmacokinetics of BMY-28100 (I)]

The pharmacokinetics of BMY-28100 have been studied in rats and monkeys upon oral administration of 14C-BMY-28100. 1. In rats administered with BMY-28100 at a single oral dose of 20 mg/kg, the peak blood level of the drug was 6.30 micrograms equiv./ml at 1 hour after administration. Blood levels declined biphasically, thereafter. The AUC value was 37.0 micrograms equiv..hr/ml, and was 97% of that observed after intravenous administration. This suggests that BMY-28100 is absorbed at a high absorption rate from the gastro-intestinal tract. 2. In monkeys administered with a single oral dose of 20 mg/kg, the peak blood level was 4.26 micrograms equiv./ml at 3 hours after administration. Thereafter, blood levels declined biphasically as did in rats. The AUC was 38.9 micrograms equiv..hr/ml, which is similar to that observed in rats. 3. Urinary and fecal excretion after 20 mg/kg oral administration were 60.9% and 38.1%, respectively, in rats, and 40.3% and 51.2%, respectively, in monkeys. 4. Although absorption from gastro-intestinal tract was delayed by food intake, this did not affect the total amount absorbed in rats. 5. The absorption rates were similar in rats administered with 20 and 60 mg/kg, while a lower rate was obtained with 200 mg/kg. 6. In rats, biliary excretion was 28.5% of dose administered. Thirty-nine percent of the biliary radioactivity was reabsorbed from the intestinal tract. 7. No differences between sexes were observed in absorption and excretion in rats administered with the drug at 20 mg/kg orally. 8. In rats administered with 20 mg/kg, the radioactivity distributed rapidly to the whole body. High levels of radioactivity were found in gastro-intestinal tract, kidney, urinary bladder, aorta and liver. The radioactivity was removed rapidly from the tissues. Autoradiograms of the whole body were consistent with the measured tissue distribution. Relatively high levels of radioactivity were found in aorta, fascia, and ligament at 0.5, 1, 6, and 24 hours. 9. In vivo protein binding, which increased with time after administration, was 56.8 to 73.5% in rat and 36.3 to 58.6% in monkey. The in vitro protein binding at 0.4 to 50 micrograms/ml of drug concentration was 50.0 to 54.7% in rat, 32.3 to 35.0% in monkey, and 33.4 to 36.3% in human. 10. A stability test of 14C-BMY-28100 in plasma solution showed that the drug decomposed gradually into relatively polar compound(s). At 8 and 24 hours, the proportions of unchanged 14C-BMY-28100 were 53.2% and 5.9%, respectively.

[Mutagenicity tests of etoposide and teniposide]

Mutagenicities of Etoposide (VP 16-213) and Teniposide (VM-26), podophyllotoxin derivatives with antitumor activity, were studied by Rec-assay, Salmonella/microsome reverse mutation assay (Ames' test) and Micronucleus test. In the Rec-assay, both Etoposide and Teniposide showed positive results on B. subtilis H17 rec+ and M45 rec-. They also induced the revertants of S. typhimurium TA 98, TA 1537 and TA 1538, but not of S. typhimurium TA 100, TA 1535 or E. coli WP2 uvrA in the Reverse mutation test. The results were not influenced by the addition of S-9 Mix. In the Micronucleus test, Etoposide and Teniposide induced significantly micronucleated polychromatic erythrocytes of the bone marrow cells in mice; 3.3-4.3% at the doses of 0.75-6 mg/kg and 4.0-6.1% at 0.5-4 mg/kg, respectively. These results indicate that Etoposide and Teniposide are both mutagenic.

[Studied on protein binding of cefadroxil and some other cephalosporins (author's transl)]

1. Human serum protein binding of cefadroxil and some other cephalosporins were determined by centrifugal ultrafiltration (U.F.) method and equilibrium dialysis (E.D.) method. The binding rates of cefadroxil were 28.1% by U.F. method and 3.8% (beta 1*), 11.6% (beta 2*) by E.D. method. 2. Protein binding of cefadroxil with sera of various animal species were also determined by E.D. method. The binding rates were low as well as that with human serum. 3. With two popular calculation formula for E.D. method, binding rate was considered on the alteration of the ratio of V2/V1.

[Pharmacokinetics of cefadroxil in rats: comparison of fasting and non-fasting (author's transl)]

A single dose 50 mg/kg of cefadroxil was administered orally to rats in fasting and non-fasting. In both fasting and non-fasting, the serum levels of cefadroxil were higher than those of cephalexin. In fasting, the biological half-life (T 1/2) of cefadroxil was longer than that of cephalexin. This indicates its prolonged durable action. Ingestion of cefadroxil with food affected the serum level less than that of cephalexin with food, and the serum levels of cefadroxil in non-fasting were same as those of cephalexin in fasting.

[Microbiological assay method of cefadroxil in biological specimens (author's transl)]

A microbiological method for quantitative determination of cefadroxil in biological specimens is described. This method is essentially a cylinder-plate or a paper-disc method using Micrococcus luteus ATCC 9341 as the test organism grown in the tryptosoya broth added with 1.5% agar. Cefadroxil standard calibration curves are prepared in pooled human serum, moni-trol I or consera for the determination of serum level of human, and 0.1 M phosphate buffer (pH 6.0) to determine urine level. Cefadroxil in human serum and urine specimens can be measured by cylinder-plate method as low as 0.16 approximately 0.31 micrograms/ml and 0.08 approximately 0.16 micrograms/ml, respectively. Further, any active metabolites of cefadroxil were not detected on human and rat urine specimens by bioautography.