PubMed Health⌕ Search

Biomedical subjects

F M Balis

Publications and source records attributed to F M Balis.

At least 73 records · Page 4Linked to original sources
PubMed1995

Carboxypeptidase-G2 rescue in a patient with high dose methotrexate-induced nephrotoxicity.

BACKGROUND: High dose methotrexate (HDMTX) induced renal failure is a medical emergency, as methotrexate (MTX) is primarily eliminated by renal excretion. High doses of leucovorin (LV) do not necessarily prevent toxicity in the presence of sustained elevated plasma MTX concentrations. The bacterial enzyme carboxypeptidase-G2 (CPDG2) hydrolyzes MTX into inactive metabolites and has been demonstrated to lower plasma MTX concentrations to nontoxic levels rapidly in the nonhuman primate after HDMTX infusion. Therefore, CPDG2 was evaluated as a rescue agent in a patient with acute renal dysfunction secondary to HDMTX: METHODS: A 16 year old patient with osteosarcoma experienced acute renal dysfunction after HDMTX administration, which resulted in markedly elevated and sustained plasma MTX concentrations. She received three doses of CPDG2 on the fifth day after HDMTX: Plasma MTX concentrations were determined before and after CPDG2 administration. RESULTS: The plasma MTX concentrations decreased from 60 to 1.2 microM within 15 minutes after the first dose of CPDG2. No rebound increase in plasma MTX concentrations or adverse reactions to the enzyme were observed. The patient developed only mild mucositis. Serum creatinine at the time of CPDG2 administration was 5 mg/dl and returned to normal within 7 weeks of enzyme administration. CONCLUSIONS: Carboxypeptidase-G2 rapidly, markedly, and persistently lowered plasma MTX concentrations to a level that could be rescued safely with LV. Based on the experience with this patient and on preclinical studies in nonhuman primates, CPDG2 appears to be more effective than hemodialysis or hemoperfusion, and may prove beneficial for patients at risk for life-threatening toxicity secondary to delayed excretion of MTX.

Acute Kidney Injury↗
PubMed1995

Pharmacokinetics of 9-cis-retinoic acid in the rhesus monkey.

9-cis-Retinoic acid is a naturally occurring biologically active retinoid capable of binding and transactivating both the retinoic acid receptors and the retinoid X receptors. A study was performed to characterize the pharmacokinetics 9-cis-retinoic acid following i.v. bolus administration in the nonhuman primate. Groups of three animals received i.v. bolus doses of 9-cis-retinoic acid of either 50 or 100 mg/m2. Blood and cerebrospinal fluid samples for determination of 9-cis-retinoic acid concentration were obtained prior to and 5, 10, 15, 30, 45, 60, 75, 90, 120, 150, 180, 240, 360, and 480 min following drug administration. The plasma drug concentration profile of 9-cis-retinoic acid was consistent with a first-order elimination process, with a harmonic mean half-life of 31 min, and a mean clearance of 97 ml/min/m2. The pharmacokinetics of 9-cis-retinoic acid were linear over the dose range studied. Plasma concentrations of all-trans-retinoic acid following 9-cis-retinoic acid administration were less than the limit of quantitation (0.1 microM), suggesting that isomerization to all-trans-retinoic acid is not a major metabolic pathway. In contrast to all-trans-retinoic acid, the elimination of 9-cis-retinoic acid did not appear to be capacity limited (saturable). Previous studies in the Rhesus monkey have shown that repeated dosing with all-trans-retinoic acid leads to a reduction of this saturable component of elimination and results in reduced exposure to drug. These studies, in an animal model highly predictive of humans, suggest that declines in plasma concentrations of 9-cis-retinoic acid as a result of its repeat administration at doses up to 100 mg/m2 will not occur.

Animals↗
PubMed1995

Intrathecal administration of topotecan in nonhuman primates.

The cerebrospinal fluid (CSF) pharmacokinetics of topotecan were studied in a nonhuman primate model following intraventricular administration of 0.1 mg. Lactone and total drug concentrations were measured using a reverse-phase HPLC method with fluorescence detection. The mean peak concentrations of lactone and total drug in ventricular CSF were 83 +/- 18 microM and 88 +/- 25 microM, respectively. CSF drug elimination of the lactone was bi-exponential with a terminal half-life of 1.3h. The mean clearance from ventricular CSF was 0.075 ml/min for the lactone and 0.043 ml/min for total drug. The ventricular CSF drug exposure (AUC) to lactone was 450-fold greater following intraventricular administration of 0.1 mg topotecan than after systemic intravenous administration of a 40-fold higher dose (10 mg/m2). Peak lumbar concentrations (n = 1), which occurred 2 h after intraventricular drug administration, were 0.98 microM and 2.95 microM for the lactone and total drug, respectively. A transient CSF pleocytosis was observed in one animal following intralumbar topotecan administration and in one animal following intralumbar topotecan administration. No other acute or chronic neurologic or systemic toxicities were observed following a single intraventricular dose or weekly (x4) intralumbar topotecan. Compared with systemic topotecan, intrathecal administration provided a significant pharmacokinetic advantage in terms of CSF drug exposure and did not produce any significant neurotoxicity in a nonhuman primate model. Intrathecal topotecan should be evaluated clinically as a potential alternative therapy for refractory meningeal tumors.

Animals↗
PubMed1995

Pharmacokinetics and tolerability of ventricularly administered superoxide dismutase in monkeys and preliminary clinical observations in familial ALS.

The discovery of mutations in the gene for Cu/Zn superoxide dismutase (SOD) in some cases of familial amyotrophic lateral sclerosis (FALS) provides a rationale for enzyme replacement therapy. The inability of SOD to cross the blood-brain barrier motivated this study of the safety, tolerability and pharmacokinetics of bovine SOD (bSOD) administered into the CSF of rhesus monkeys and one late-stage, SOD-deficient FALS patient. Kinetic analyses in the patient indicated that intracerebroventricular (i.c.v.) administration, but not lumbar administration, delivered bSOD to the entire CSF pathway. Daily bolus i.c.v. injections (32 mg/day) and continuous i.c.v. infusion (30 mg/day) were well tolerated by the patient. During the period of daily bolus injections, the patient's performance on manual muscle tests was nearly stable, in contrast with the rapid decline before and after that period. These results justify further investigation of bSOD therapy in SOD-deficient FALS patients.

Amyotrophic Lateral Sclerosis↗
PubMed1995

Pharmacokinetics of lamivudine and BCH-189 in plasma and cerebrospinal fluid of nonhuman primates.

2'-Deoxy-3'-thiacytidine is a dideoxycytidine analog with a sulfur in place of the 3' carbon of the ribose. There are two enantiomeric forms of the compound, both of which inhibit human immunodeficiency virus type 1 and 2 replication in vitro. However, the (-) enantiomer (lamivudine) appears to be significantly less cytotoxic to uninfected lymphocytes than is the (+) enantiomer. Lamivudine has entered initial clinical trials, and the present study was designed to describe the pharmacokinetic behavior of this compound in both plasma and cerebrospinal fluid (CSF) of primates. Lamivudine was administered as an intravenous bolus dose of 20 mg/kg for 24 h for administration. Urine samples were also obtained from two animals. The same dose of the racemate (BCH-189) was administered to one animal. The drug was quantitated in CSF and plasma with a reverse-phase high-pressure liquid chromatography technique. Elimination of lamivudine from plasma was biexponential, with a mean alpha phase half-life of 5.4 min, a mean beta phase half-life of 84 min, and a total clearance of 6.1 liters/h. The total clearance of the same dose of BCH-189 in a single animal was 11.0 liters/h. In two animals from which urine was obtained for 12 h postadministration, 32 and 59% of the drug was recovered unchanged. The deamination product of lamivudine was not detected. The CSF/plasma ratio of lamivudine was significantly higher when the drug was measured in the lumbar CSF (mean, 0.41) than when it was measured in the ventricular CSF (mean, 0.079). The measured CSF/plasma ratio for ventricular CSF is equivalent to that of other dideoxycytidine analogs, confirming the importance of the nucleobase in determining the degree of CSF penetration. The difference in lamivudine exposure in ventricular and lumbar CSF suggests that there is a transport mechanism for efflux of cytidine analogs from ventricular CSF.

Animals↗
PubMed1995

Pharmacokinetics of dideoxypurine nucleoside analogs in plasma and cerebrospinal fluid of rhesus monkeys.

The pharmacokinetics of 2',3'-dideoxyadenosine (ddA), didanosine, 2',3'-dideoxyguanosine (ddG), and 6-halogenated prodrugs of ddG, 6-chloro-ddG and 6-iodo-ddG, in plasma and cerebrospinal fluid (CSF) were studied in a non-human primate model. ddA was rapidly and completely deaminated to didanosine, such that didanosine concentration profiles in plasma and CSF were identical following administration of ddA and didanosine. The mean clearance of didanosine was 0.50 liters/h/kg, the terminal half-life was 1.8 h, and the CSF-to-plasma ratio was 4.8%. The disposition of ddG was similar, with a clearance of 0.70 liters/h/kg and a half-life of 1.7 h. The adenosine deaminase-mediated conversion of the 6-halogenated-ddG prodrugs to ddG was rapid but incomplete (48% for 6-chloro-ddG and 29% for 6-iodo-ddG). The CSF-to-plasma ratios of ddG with equimolar doses of ddG, 6-chloro-ddG, and 6-iodo-ddG were 8.5, 24, and 17%, respectively, but the actual ddG exposures in CSF (area under the CSF concentration-time curve) were comparable for ddG (12.1 microM.h) and the 6-halogenated-ddG prodrugs (18.8 microM.h for 6-chloro-ddG, 9.3 microM.h for 6-iodo-ddG).6-Chloro-ddG was not detectable in plasma or CSF, and the CSF-to-plasma ratio of 6-iodo-ddG was 9.4%, so the higher CSF-to-plasma ratios of ddG with the administration of the 6-halogenated-ddG prodrugs does not appear to be the result of enhanced penetration of the prodrug and subsequent dehalogenation to ddG. The penetration of ddG into CSF exceeds that of didanosine and is enhanced by administration of the 6-halogenated prodrugs, although the mechanism of this enhanced penetration is unclear.

Animals↗
PubMed1995

Effect of body position on ventricular CSF methotrexate concentration following intralumbar administration.

PURPOSE: Intralumbar methotrexate is one of the primary therapeutic modalities for the prevention and treatment of meningeal leukemia. However, methotrexate distribution to the ventricles is limited and highly variable following intralumbar dosing, and cytotoxic concentrations of methotrexate are not always achieved or sustained in the ventricular CSF. We used a nonhuman primate model to determine the effect of body position on the caudal distribution of an intralumbar dose of methotrexate. METHODS: Methotrexate (1.0 mg) was administered by intralumbar injection to four animals, which were then immediately placed either in an upright sitting position or in a prone position for 1 hour, then upright. Each animal served as its own control and was studied in each position on at least one occasion. RESULTS: The mean peak ventricular methotrexate concentration was 0.12 mumol/L (range, 0.091 to 0.20) in animals that were immediately placed upright, compared with 2.81 mumol/L (range, 0.21 to 8.9) in animals that remained prone for 1 hour. The mean area under the concentration-versus-time curves (AUC) was 0.51 mumol/L.h (range, 0.26 to 1.1) in the upright animals and 12.0 mumol/L.h (range, 0.9 to 35.4) in the prone animals. CONCLUSION: Maintaining a prone position for 1 hour after an intralumbar dose increased the peak methotrexate concentration and drug exposure in ventricular CSF. CSF drug distribution following intralumbar therapy can be influenced by body position after the injection.

Animals↗
PubMed1995

Pharmacokinetics of all-trans-retinoic acid administered on an intermittent schedule.

PURPOSE: Administration of all-trans-retinoic acid (ATRA) on a continuous daily schedule results in a rapid and sustained decrease in plasma drug concentrations. This pharmacokinetic study was performed to determine if administration of ATRA on an intermittent schedule could overcome the rapid decrease in plasma drug concentration and provide repetitive periods of higher plasma drug exposure. MATERIALS AND METHODS: ATRA was administered on repetitive cycles of 7 consecutive days of drug followed by 7 days without drug. On the days of pharmacokinetic monitoring, following an overnight fast, a fixed single oral dose of 40 mg/m2 was administered and frequent plasma samples were obtained over 8 hours. Patients had pharmacokinetic studies performed on the first and seventh days of the first week, and on the first day of the third and eleventh weeks. ATRA was measured in plasma with a reverse-phase high-performance liquid chromatography (HPLC) assay. RESULTS: Plasma exposure to ATRA as measured by the area under the plasma concentration-time curve (AUC) decreased significantly during the first week of drug administration, from a mean of 145 +/- 26 mumol/L.min on day 1 to 18 +/- 4 mumol/L.min by day 7. Plasma ATRA concentrations at the start of weeks 3 and 11 of this every-other-week schedule were equivalent to those achieved on day 1 of treatment, with mean AUCs of 177 +/- 39 and 128 +/- 30 mumol/L.min, respectively. CONCLUSION: An intermittent schedule of ATRA administration results in repetitive periods of exposure to concentrations of ATRA normally only observed on the first day of treatment. Phase II trials to evaluate the role of intermittent schedules of administration for ATRA are planned.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Phase I and pharmacokinetic study of the multidrug resistance modulator dexverapamil with EPOCH chemotherapy.

PURPOSE: Dexverapamil is a competitive inhibitor of the P-glycoprotein (Pgp) efflux pump, a potent mechanism of multidrug resistance (mdr-1) in vitro. We performed a phase I study to determine the maximum-tolerated dose (MTD) and pharmacokinetics of dexverapamil with etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (EPOCH) chemotherapy. PATIENTS AND METHODS: Eligible patients had relapsed or refractory lymphoma or sarcoma. Patients initially received EPOCH alone, and those with stable or progressive disease were crossed-over to received dexverapamil on subsequent cycles of EPOCH. Dexverapamil was administered orally for 6 days and escalated over eight dose levels ranging from 240 to 1,200 mg/m2/d. Pharmacokinetics of dexverapamil and its active metabolite, nor-dexverapamil, were obtained in most patients. In seven patients, pharmacokinetics of doxorubicin, doxorubicinol, and etoposide were determined on paired cycles of EPOCH with or without dexverapamil. RESULTS: Sixty-five patients received 130 cycles of dexverapamil/EPOCH chemotherapy. The MTD of dexverapamil was 150 mg/m2 every 4 hours (900 mg/m2/d), and hypotension was the principal dose-limiting toxicity. The dexverapamil area under the curve (AUC) increased proportionally with dexverapamil dose, but significant interpatient variation occurred. At the MTD, the median plasma average concentrations of dexverapamil and nor-dexverapamil were 1.2 and 1.4 mumol/L, respectively. Dexverapamil did not affect the steady-state concentration (Css) of etoposide, but increased the Css of doxorubicin and doxorubicinol nearly twofold. The absolute neutrophil and platelet nadirs were significantly lower on the dexverapamil cycles compared with cycles of EPOCH alone, but other chemotherapy-related toxicities did not change. CONCLUSION: The phase II recommended dose of dexverapamil with EPOCH is 150 mg/m2 every 4 hours. This dose was well tolerated on an outpatient basis and achieved plasma concentrations of dexverapamil and nor-dexverapamil within the effective range for Pgp inhibition in vitro. Although dexverapamil increased the hematopoietic toxicity of EPOCH, it was mild, readily reversible, and offset by EPOCH dose reductions. Dexverapamil should be considered for further study.

Adult↗
PubMed1995

Effect of R-verapamil on the pharmacokinetics of paclitaxel in women with breast cancer.

PURPOSE: To study the effect of the multidrug-resistance reversal agent R-verapamil on the pharmacokinetic behavior of paclitaxel. METHODS: Six women with breast cancer who received paclitaxel as a 3-hour infusion with and without R-verapamil were monitored with frequent plasma sampling up to 24 hours postinfusion. Paclitaxel concentrations were measured using a reverse-phase high-pressure liquid chromatography assay. RESULTS: Concomitant administration of R-verapamil resulted in a decrease in mean (+/- SD) paclitaxel clearance from 179 +/- 67 mL/min/m2 to 90 +/- 34 mL/min/m2 (P < .03) and in a twofold increase in paclitaxel exposure (area under the curve [AUC]). The mean end-infusion paclitaxel concentration was also twofold higher: 5.1 +/- 1.8 mumol/L versus 11.3 +/- 4.1 mumol/L (P < .03). CONCLUSION: The alteration in paclitaxel pharmacokinetics when paclitaxel and R-verapamil are coadministered complicates the interpretation of response and toxicity data from clinical trials of this drug combination.

Breast Neoplasms↗
PubMed1994

A pharmacokinetic model of topotecan clearance from plasma and cerebrospinal fluid.

We present a physiological pharmacokinetic model that describes the plasma and cerebrospinal fluid (CSF) concentrations of topotecan [(S)-9-dimethylaminomethyl-10-hydroxyamptothecin hydrochloride, SK&F 104864-A, NSC 609699] following i.v. and intraventricular administrations in monkeys. The model consists of three physical spaces: the CSF, the plasma, and a body compartment. The model incorporates such processes as reversible conversion of topotecan lactone to an inactive hydroxy acid form, microvascular exchange between CSF and plasma, bulk CSF flow, exchange between plasma and body compartments, and elimination of drug from the plasma compartment. Several parameters in the model were obtained from published literature on the physiology of the monkey. The model was then fit to the plasma and CSF data to deduce the other parameters. Calculated clearances of topotecan lactone and total drug from the CSF after intraventricular injection were 3.9 and 2.2 ml/h, respectively. Clearances of topotecan lactone and total drug from the plasma following a 10-min infusion were 26.3 liters/h/m2 and 17.8 liters/h/m2, respectively. The calculated ratios of the area under the concentration curve in the CSF following i.v. infusion to the area under the concentration curve in plasma were 0.11 and 0.19 for topotecan and total drug, respectively, indicating significant CSF penetration. The volume of distribution was 0.77 liters/kg, which represents distribution in a volume approximating total body water. The forward and reverse rate constants for the lactone-to-hydroxy acid conversion were 1.0 and 0.29 h-1, respectively. Comparison of the clearances (normalized to body surface area) with values reported for mice and humans shows reasonable similarity across species. This pharmacokinetic model may help guide future development and refinement of clinical protocols, especially in the treatment of diseases of the central nervous system.

Animals↗
PubMed1994

Acute pancreatitis after ifosfamide therapy.

Acute pancreatitis is an uncommon but serious complication of cancer chemotherapy. A 16-year-old girl with metastatic osteosarcoma experienced recurrent bouts of symptomatic pancreatitis 24 hours after treatment with ifosfamide administered as a single agent. To the authors' knowledge, this is the first report of an association between ifosfamide and pancreatitis. Because serum amylase levels are not monitored routinely during treatment with most chemotherapeutic agents, subclinical cases of pancreatitis with ifosfamide and other agents may go undetected.

Acute Disease↗
PubMed1994

The cytotoxicity of thioguanine vs mercaptopurine in acute lymphoblastic leukemia.

The use of mercaptopurine (MP) rather than thioguanine (TG) in the treatment of childhood acute lymphoblastic leukemia (ALL) has occurred for historical reasons, but does not have a pharmacologic basis. The purpose of this study was to begin to address whether TG would be more efficacious than MP in the treatment of childhood ALL. Preclinical cytotoxicity studies were performed using human leukemic cell lines and leukemic cells from patients with ALL. First, the concentration-survival curves for MP and TG in three human leukemic cell lines (MOLT-4, CCRF-CEM and Wilson) were determined. The second group of experiments determined the concentration-time dependence for cytotoxicity of MP and TG. The final group of experiments compared the in vitro cytotoxicity of MP to TG in leukemic cells from patients with ALL. The thiopurines displayed classical anti-metabolite cytotoxicity profiles, exhibiting a cytotoxicity threshold concentration and demonstrating an increase in cell kill with prolongation of exposure to the drug. For MP, the cytotoxicity threshold was approximately 1 microM, with maximum cytotoxicity occurring with 10 microM concentrations. For TG, the threshold was only 0.05 microM with maximum cytotoxicity occurring at 0.5 microM. Exposure to MP for more than 8 h was necessary to produce cytotoxicity, whereas exposures as short as 4 h were required for TG. Leukemic cells from children with ALL were also more sensitive to TG than to MP. The median IC50 for TG (20 microM) was significantly lower than that for MP (> or = 206 microM). The data presented here provide a strong rationale for evaluating TG in place of MP in the treatment of childhood ALL. The more direct intracellular activation pathway, higher potency, and shorter duration of drug exposure necessary for cytotoxicity all suggest that TG may have an advantage over MP.

Adolescent↗
PubMed1994

Quantitative relationships between zidovudine exposure and efficacy and toxicity.

We examined the relationship between the concentrations of zidovudine in plasma given by continuous intravenous infusion to human immunodeficiency virus-positive pediatric patients and a surrogate marker of outcome (measured by the increase in the number of CD4-positive T cells) as well as drug-mediated toxicity (change in granulocyte count). The return of CD4-positive T cells was most strongly related to the number of these cells present at the start of therapy. Drug concentration data added little explanatory power to this relationship, indicating that the effect of zidovudine was near maximal throughout the range of concentrations examined. The change in granulocyte count was significantly correlated with zidovudine concentration both from weeks 1 through 8 and from weeks 8 through 12. These findings imply that it may be wise to stratify phase I antiretrovirus drug trials for the entry level of CD4-positive T cells if pharmacodynamic relationships with this marker as the dependent variable are to be sought. Continued efforts need to be made to derive quantitative relationships between drug exposure and measures of both efficacy and toxicity so that the maximal amount of information is derived from small phase I studies.

CD4 Lymphocyte Count↗
PubMed1994

Zidovudine and didanosine combination therapy in children with human immunodeficiency virus infection.

OBJECTIVE: Zidovudine and didanosine are both beneficial for the treatment of human immunodeficiency virus (HIV) infection in children. Because disease progression and toxicity often limit their long-term use as single agents, new approaches to using nucleoside analogues are necessary to improve current antiretroviral therapy. DESIGN: We conducted a phase I-II study to evaluate the tolerance, pharmacokinetics, and antiviral activity of the combination of zidovudine and didanosine in children with HIV infection. Sixty-eight children who were either previously untreated or who had manifested hematologic toxicity on full-dose zidovudine were enrolled. Eight dose combinations were studied in the previously untreated children, with doses of zidovudine ranging from 90 to 180 mg/m2 every 6 hours and doses of didanosine ranging from 90 to 180 mg/m2 every 12 hours. RESULTS: Fifty-four previously untreated HIV-infected children were enrolled in this part of the study, of whom 49 remained in the study for a minimum of 24 weeks. For children with previous zidovudine-related hematologic toxicity, three dose levels with zidovudine at 60 mg/m2 every 6 hours orally and didanosine ranging from 90 to 180 mg/m2 every 12 hours orally were used. A total of 14 children were enrolled in this part of the study, and 12 remained on therapy for at least 24 weeks. No evidence of new or enhanced toxicity was observed in either group. After 24 weeks, the median CD4 cell count for all patients increased from 331 to 556 cells/mm3 (P = .01). For the previously untreated group, the median increase in CD4 counts was from 386 to 726 cells/mm3 (P = .003). The median p24 antigen concentration (in those with a detectable level at baseline) decreased from 95 to < 31 pg/mL (p < .001). The geometric mean titer of HIV in plasma decreased from 83.1 to 2.7 tissue culture infectious doses/mL (P = .001). CONCLUSIONS: The combination of zidovudine and didanosine was well-tolerated at doses as high as those used in single agent therapy. Potent in vivo antiviral activity was observed. Combination therapy with nucleoside analogues may be an important approach to optimizing the use of these agents in the treatment of HIV infection.

Adolescent↗