Similar bioavailability of single-dose oral and intravenous mesna in the blood and urine of healthy human subjects.

Although mesna has been used for more than a decade to reduce the incidence of hemorrhagic cystitis induced by ifosfamide and cyclophosphamide, the disposition of i.v. and oral mesna has not been adequately described. To obtain accurate bioavailability data for the design of mesna regimens, we developed procedures to preserve and measure mesna and dimesna in the blood and urine and studied 25 volunteer subjects who received single doses of i.v. mesna and four different formulations of oral mesna in a five-way randomized crossover study. The dose-adjusted area under the blood concentration-time curve showed no difference in bioavailability for i.v. and oral mesna; however, the maximum mesna concentration after oral doses was 16% of that estimated for i.v. doses. The short initial half-life of i.v. mesna indicated that mesna was rapidly cleared; however, the blood concentrations of mesna uniformly exceeded those of dimesna after oral as well as i.v. doses, which suggested that reduced mesna and oxidized mesna disulfide are in equilibrium. The ratio of mesna:dimesna was higher in protein-free plasma than it was in the urine, which suggested that most urinary mesna is produced by glomerular filtration of mesna rather than by renal tubular reduction of dimesna. The sum of mesna and dimesna excretion after the i.v. doses (73% of the dose) and the four oral formulations (68-73%) showed no difference in urinary bioavailability, consistent with the blood data. However, the urinary bioavailability of the therapeutically active free-thiol mesna was greater after i.v. doses (40% of the dose) than it was after oral doses (31-33%). The ratio of oral:i.v. mesna excretion ranged from 0.52-1.23 (mean, 0.82) among the 24 subjects. Urinary mesna concentrations exceeded 50 microM in all subjects for up to 12 h after oral doses as compared to 4 h after i.v. doses. About 90% of this mesna was excreted by hour 2 after i.v. doses and by hour 9 after oral doses. The mean maximum concentration of mesna in blood and excretion into urine were both 2.6 h after dosing. The oral formulations thus showed sustained urinary excretion, and their urinary bioavailability approached that of i.v. mesna.

Reduction of dimesna to mesna by the isolated perfused rat liver.

Mesna is administered with ifosfamide and cyclophosphamide to reduce the incidence of hemorrhagic cystitis. In the present model of mesna metabolism and disposition, mesna is rapidly and irreversibly oxidized to dimesna in the plasma, passes unchanged through the liver, and is then reduced by the kidney and excreted. Our detection of a high ratio of mesna to dimesna in the plasma of clinical samples led us to reinvestigate the hepatic metabolism of mesna and dimesna. We perfused isolated rat livers from female Sprague Dawley rats with protein-free buffered solution containing dimesna at concentrations observed during therapy. In single-pass perfusions, each liver was perfused with up to three dimesna concentrations during consecutive 20-min periods. Recirculating perfusions were used to study single supratherapeutic concentrations of dimesna or mesna. Mesna and dimesna concentrations were measured by specific chromatographic procedures. Dimesna reduction, adjusted by the effluent flow rate and liver weight (0.4-58.5 nmol/min/g liver), correlated closely by linear regression (r = 0.98; n = 36) to the perfused dimesna concentration (4.2-249 microM), indicating a clearance of 0.20 ml/min/g liver. The concentration of dimesna that entered the liver closely matched the summed concentration of mesna and dimesna emerging in the effluent perfusate (single-pass experiments: slope, 0.98; intercept, -0.30; r = 1.00; n = 31). Only trace amounts of unidentified thiols were detected in the bile during recirculation of perfusates with 1 mM mesna or 250 microM dimesna. The effluent mesna concentration correlated inversely with the flow rate, which was consistent with a low extraction ratio in the perfusion model. These data suggested that the dimesna reduction rate was limited by hepatic uptake. Dimesna reduction was decreased by agents that deplete glutathione. Pretreatment of rats with up to 100 mg/kg ifosfamide did not impair hepatic dimesna reduction. In control experiments, dimesna was not reduced during recirculation through the apparatus without a liver. Mesna was oxidized to dimesna during oxygenation of the perfusate in the reservoir, but mesna injected directly into the perfusate just before entry into the liver passed unchanged into the effluent. Extrapolation of the dimesna clearance data from the perfusion model to humans suggests that hepatic dimesna reduction may counterbalance the rapid oxidation of mesna in plasma. The proposed equilibrium is consistent with clinical observations and suggests a new model for mesna metabolism and disposition.

Pharmacokinetics of an intravenous-oral versus intravenous-mesna regimen in lung cancer patients receiving ifosfamide.

PURPOSE: To compare the pharmacokinetics of the approved I.V. (intravenous) mesna regimen and an investigational I.V.-oral regimen that could be used in outpatients who receive ifosfamide. PATIENTS AND METHODS: The I.V. regimen consisted of three I.V. mesna doses given at 0, 4, and 8 hours after ifosfamide administration. The investigational regimen included an I.V. mesna dose given concurrently with ifosfamide, followed 2 and 8 hours later by oral administration of mesna tablets. I.V. and oral mesna doses equaled 20% and 40%, respectively, of the ifosfamide dose. The study subjects were 12 lung cancer patients who received ifosfamide 1.2 g/m2 daily for 5 days. The patients were randomized to receive either the I.V.-oral or I.V. mesna regimen on day 1, followed by crossover to the other regimen on days 2 through 5 of ifosfamide treatment. The urinary profiles of mesna and dimesna excretion were determined on days 1, 2, and 5; pharmacokinetic parameters for blood samples were determined only on day 5. RESULTS: During the first 12 hours after ifosfamide administration, the amount of mesna excreted and the profile of urinary mesna excretion was similar for both regimens; however, the I.V.-oral regimen showed less fluctuation in the excretion rate and higher trough values. During hours 12 to 24, about eightfold more mesna was excreted by patients given the I.V.-oral than the I.V. regimen. CONCLUSION: These pharmacokinetic data show that the I.V.-oral regimen should be at least as uroprotective as the I.V. mesna regimen. Patients may also benefit from the I.V.-oral regimen because of the higher trough values during hours 0 through 12 and the sustained urinary mesna excretion during hours 12 through 24.

Toxicity, pharmacokinetics, and in vitro hemodialysis clearance of ifosfamide and metabolites in an anephric pediatric patient with Wilms' tumor.

PURPOSE: We evaluated the in vitro hemodialysis ratio and subsequent toxicity and pharmacokinetics of ifosfamide in an anephric patient with Wilms' tumor. METHODS: An in vitro model was used to determine the extraction ratio of ifosfamide by dialysis. The toxicity and plasma concentrations of ifosfamide, chloroacetaldehyde, and 4-hydroxyifosfamide were then determined over 24 h after a single 1.6 g/m2 dose of ifosfamide. Plasma concentrations were also measured before and after ten dialysis sessions during four courses of ifosfamide therapy. RESULTS: The in vitro hemodialysis model showed that ifosfamide was cleared with an extraction ratio of 86.7+/-0.5% and remained constant even at low concentrations of drug. The mean decrease in vivo following hemodialysis for ifosfamide, chloroacetaldehyde, and 4-hydroxyifosfamide were 86.9%, 77.2%, and 36.2%, respectively. The pharmacokinetic parameters for ifosfamide using model-independent methods were calculated: Vd = 0.23 l/kg, t1/2 = 4.8 h, and ClT = 3.30 l/h per m2. Ifosfamide-associated neurotoxicity was noted within hours of drug administration and improved rapidly following hemodialysis. CONCLUSIONS: The results of our study suggest that the pharmacokinetics of parent ifosfamide may not be substantially altered in patients with renal failure. Hemodialysis was shown to remove ifosfamide, chloroacetaldehyde, and 4-hydroxyifosfamide from the blood stream. Hemodialysis was also shown to reverse ifosfamide-related neurotoxicity.

Combined intravenous and oral mesna in outpatients treated with ifosfamide.

PURPOSE: To prevent hemorrhagic cystitis, mesna is typically injected intravenously (i.v.) at the time of an ifosfamide dose and 4 and 8 h later. To simplify outpatient ifosfamide therapy, we gave the second and third mesna doses orally. METHODS: The mesna doses (400 or 600 mg/m2) were 40% (w/w) of each ifosfamide dose (1.0 or 1.5 g/m2), which was given daily for 5 days. We evaluated urinary mesna excretion and plasma concentrations in ten patients from the beginning of mesna infusion until the time of the second oral dose. The first oral dose was administered at hour 2 in the last six patients to allow time for absorption of mesna. RESULTS: The rate and amount of mesna excretion was less variable over time and among patients after oral than after i.v. administration. No macrohematuria was observed in these ten patients nor in an additional 50 patients given oral mesna at hours 2 and 8 during at least two cycles of ifosfamide therapy. CONCLUSION: These pharmacokinetic and clinical efficacy data support the use of a combined regimen of i.v. and oral mesna to simplify outpatient ifosfamide administration.

Oral administration of mesna with ifosfamide.

Mesna can be given orally to simplify outpatient ifosfamide therapy. Oral administration of mesna solution or tablets has been approved in Canada, Denmark, Germany, Italy, The Netherlands, and the United Kingdom, and programs for registration are ongoing in other European countries and in the United States. This review summarizes dosing schedules and the incidence of hematuria in 47 clinical studies, in which oral mesna was given to at least 1,986 patients who received more than 6,475 courses of ifosfamide. Various doses and schedules of oral mesna, usually in combination with intravenously injected mesna, provided effective uroprotection for a wide range of ifosfamide regimens.

Oral mesna: a review.

Oral administration of mesna can facilitate outpatient ifosfamide therapy. Blood and urinary mesna concentrations are more steady and prolonged after oral delivery compared with after intravenous delivery. The incidence of hematuria observed during partial oral mesna therapy is no greater than that during intravenous mesna therapy. The pharmacology, pharmacokinetics, efficacy, safety, and reported schedules of administration are reviewed.

Determination of urinary 2- and 3-dechloroethylated metabolites of ifosfamide by high-performance liquid chromatography.

In vivo oxidation of chloroethyl side-chains on ifosfamide produces the toxin chloroacetaldehyde. Production of this labile metabolite can be indirectly quantitated by monitoring the excretion of the residual 2- and 3-dechloroethylated ifosfamide. Urinary ifosfamide and the two dechloroethylated metabolites were extracted into chloroform from alkalinized salt-saturated urine, followed by high-performance liquid chromatographic separation using an acetonitrile gradient on a reversed-phase column and ultraviolet detection at 190 nm. In five patients given 1.6 g/m2 ifosfamide, 11-30% of the dose was excreted over 24 h as unchanged drug, 11-21% as 3-dechloroethylated and 3-10% as 2-dechloroethylated ifosfamide.

Rhabdomyosarcoma and other soft tissue sarcomas of childhood.

Often treated as a single clinical entity, the pediatric soft tissue sarcomas include neoplasms of diverse histology that can originate from any anatomic site and exhibit varied patterns of local spread and metastasis. Recent developments with potential clinical impact include new diagnostic and prognostic markers stemming from advances in molecular biology, and increasing concern for the late effects of therapy in a growing population of long-term survivors. Initial clinical data indicate the value of MyoD1 protein expression in classifying previously indeterminate primitive undifferentiated tumors. The reported sensitivity and specificity of P-glycoprotein expression for the identification of chemoresistant disease in pediatric sarcomas should spawn studies to clarify its prognostic value and potential therapeutic strategies to circumvent the multidrug-resistance phenotype. Tumor cell DNA ploidy may also have prognostic and diagnostic value. An abundant interest in alleviating the late effects of adjuvant therapy and surgery is reflected in many clinical reports by oncologists, surgeons, radiotherapists, ophthalmologists, and other specialists.

The stability of mesna in beverages and syrup for oral administration.

We evaluated the stability of the aqueous formulation of mesna during storage in syringes and after dilution in beverages and syrups. Measurements of the concentrations of mesna showed that the undiluted formulation was stable for at least 9 days in standard polypropylene syringes at 5 degrees, 24 degrees, and 35 degrees C. There was no detectable oxidation of mesna to dimesna over the course of at least 1 week when mesna was diluted 1:2 and 1:5 in syrups and incubated at 24 degrees C in capped tubes. Concentration changes were clinically negligible for 1:2, 1:10, and 1:100 dilutions of mesna in six carbonated drinks, two juices, and milk after incubation for 24 h at 5 degrees C. Thus, the aqueous mesna formulation is stable when diluted and stored in a variety of beverages and syrups under conditions suitable for oral administration.

Ifosfamide neurotoxicity is related to previous cisplatin treatment for pediatric solid tumors.

Neurotoxicity developed in 22 of 97 children and adolescents with malignant solid tumors treated within a phase II ifosfamide protocol. The occurrence of neurotoxicity was related to previous cumulative dosages of cisplatin. One third of the patients who had received more than 600 mg/m2 of cisplatin developed this complication. The relative risk increased 3.2-fold with previous cisplatin dosages above 301 to 600 mg/m2, and 4.1-fold with dosages of 601 to 1,340 mg/m2. The increased risk of neurotoxicity in patients who had received more than 600 mg/m2 of cisplatin may be related to either a decreased clearance of ifosfamide itself or of the drug's active metabolites.

False-positive ketone tests: a bedside measure of urinary mesna.

The sulfhydryl mesna is increasingly used to protect the bladder and kidney from effects of chemotherapy with ifosfamide and cyclophosphamide. Mesna reacts with reagents on urinary test strips designed to detect ketones. Test-strip results were correlated to sulfhydryl concentrations in 931 urine specimens obtained after infusions of mesna. These data may be used to estimate urinary mesna concentrations at the bedside or to test compliance in outpatients given oral mesna therapy.

Mesna excretion and ifosfamide nephrotoxicity in children.

To characterize the excretion of 2-mercaptoethanesulfonate sodium (mesna) administered by intermittent infusion, urinary concentrations of mesna and its corresponding inactive disulfide were measured during 50 courses of ifosfamide (1.6 g/m2 for 5 days) and mesna (400 mg/m2 at 0.25, 4, and 6 h after each ifosfamide dose) administered i.v. to 19 patients. Some patients had previously received nephrotoxic therapy that might influence the excretion of mesna and its associated uroprotective effects. The median urinary free thiol concentration increased to 3 mM by 1 h after mesna infusion, declining to background levels by 4 h. The rate of mesna excretion correlated with the creatinine clearance rate in a subset of six patients. The proportion of mesna recovered in urine within 4 h after infusion was lower (P less than 0.05) in children who had evidence of preexisting renal tubular damage. Ifosfamide-induced tubular proteinuria was associated with lower urinary mesna recovery. Low urinary mesna concentrations indicated potentially subtherapeutic renal tubular levels. However, ifosfamide nephrotoxicity was subclinical and is not necessarily linked to differences in mesna excretion.

Agarose gel electrophoresis in isozyme separation and visualization.

Isozyme analysis of rodent-human somatic cell hybrids has been used frequently to detect specific human chromosomes. The majority of these isozyme systems employs starch gels, the use of which can be laborious when screening large numbers of cell lines. We describe the development of two procedures to detect the long arms of human chromosomes 1 and 2 in Chinese hamster-human cell hybrids by a rapid and reproducible method using 1-mm-thick agarose gels. Detection of human chromosome 1q was accomplished by screening for human fumarate hydratase activity, whose gene has been mapped to 1q42.1. Detection of chromosome 2q was performed by screening for the isozyme isocitrate dehydrogenase 1, which has been localized to 2q32-qter. These systems provide a basis for the further development of procedures for detecting chromosome-specific isozyme markers in agarose gels.

Vancomycin does not enhance amikacin-induced tubular nephrotoxicity in children.

A three-drug antibiotic regimen including vancomycin and amikacin has been recommended as effective treatment in clinical settings in which Gram-positive bacteremias are a serious problem. To determine if vancomycin potentiates the tubular proteinuria associated with amikacin therapy, we studied febrile, neutropenic children with leukemia who were treated with either amikacin (800 mg/m2/day) and ticarcillin-clavulanate or with vancomycin (1.2 g/m2/day), amikacin and ticarcillin. Tubular proteinuria was assessed in 14 children by monitoring the excretion of total urinary protein and two other sensitive indicators of nephrotoxicity, the renal tubular enzymes N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase, in sequential 8-hour urine collections during 7 days of antimicrobial therapy. There were no significant differences between the two treatment groups in excretion of the three marker proteins when values were compared on any day of therapy or for the entire 7-day course. Nor did we observe any significant changes in either serum creatinine concentrations or amikacin clearance rates in the larger study group of 101 children from which these patients were drawn. Although amikacin was subclinically nephrotoxic, the addition of vancomycin to amikacin therapy did not enhance clinical or tubular nephrotoxicity in these children.

Clinical studies of ifosfamide/mesna at St Jude Children's Research Hospital, 1983-1988.

A phase-II study of ifosfamide with mesna, given intravenously daily for five days by bolus injection, has demonstrated the activity of ifosfamide against a spectrum of childhood malignant solid tumors. Ifosfamide presently is being investigated in alternative phase-I schedules, daily times three or every other day times three with the aim of delivering comparable amounts of ifosfamide without increasing toxicity--specifically, neurotoxicity. Additionally, response following ifosfamide treatment is being evaluated for previously untreated children with osteosarcoma and rhabdomyosarcoma after 6 weeks of treatment, and for previously untreated patients with Ewing's sarcoma after 9 weeks of treatment with ifosfamide/VP-16 (etoposide) given in combination.

Ifosfamide in pediatric malignant solid tumors.

Ifosfamide/mesna was given to 97 patients who had malignant solid tumors diagnosed before they were 21 years of age. Patients received 1.6 g/m2 ifosfamide daily x 5, given i.v. over 15 min, followed by 400 mg/m2 i.v. mesna at 15 min and 4 and 6 h after ifosfamide. Responses were noted in patients with osteosarcoma, Ewing's sarcoma, rhabdomyosarcoma and other soft-tissue sarcomas, rhabdoid tumor, neuroblastoma, Wilms' tumor, primitive neuroectodermal tumor, retinoblastoma, germ-cell tumors, and B-cell lymphoma. Toxicity included mild to moderate nausea and vomiting, transient, reversible myelosuppression, transient elevations of serum blood urea nitrogen (BUN) and creatinine and liver enzymes, infections, and self-limiting neurotoxicity characterized by changes in mental status, motor dysfunction, cranial nerve palsy, cerebellar dysfunction, and seizures. Neurotoxic symptoms were generally seen in patients who had previously received cisplatin. Ifosfamide is an important alkylating agent that should be combined with other agents in phase II and III trials. Alternate dose schedules should also be investigated.

Tubular nephrotoxicity during long-term ifosfamide and mesna therapy.

The nephrotoxic effects of ifosfamide were assessed in 18 children and adolescents given cumulative doses of 32-112 g/m2 (1.6 g/m2 per day in sequential 5-day courses) with the uroprotectant mesna (1.2 g/m2 per day). Tubular nephrotoxicity was evaluated by measuring the urinary concentrations of N-acetyl-beta-D-glucosaminidase (NAG), alanine aminopeptidase (AAP), and total protein before and during sequential courses of therapy. Of 15 patients who had normal levels of tubular markers before ifosfamide therapy, only 1 developed a persistent increase in baseline values of the three tubular markers with the sixth course of ifosfamide. Although transient increases in the excretion of these markers were observed during each 5-day course of ifosfamide, the magnitude did not increase over sequential courses in these 15 patients. Of the remaining three patients who had increased NAG levels before ifosfamide therapy, two showed a progressive increase in enzymuria and proteinuria, and serum creatinine concentrations increased in a single patient who had obstructive uropathy. Our data suggest that children with normal renal function can be given large cumulative amounts of ifosfamide in fractionated doses with little risk of progressive clinical nephrotoxicity.

Monitoring serum aminoglycoside concentrations in children with amphotericin B nephrotoxicity.

We prospectively studied the effect of amphotericin B therapy on aminoglycoside clearance in 20 consecutive children during the remission-induction phase of chemotherapy for acute myelocytic leukemia. Increases (greater than 50%) in the half-life for aminoglycoside excretion were not associated with antileukemic or aminoglycoside therapy alone but occurred in 12 of 17 children when amphotericin B was added to the antimicrobial regimen. Seven children had impaired aminoglycoside clearance without increases (greater than 50%) in serum creatinine; hence the resulting adjustments in aminoglycoside dosage would not have been made had we relied solely on serial measurements of serum creatinine. Evidence for increased excretion of the renal enzymes N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase during amphotericin B therapy suggested that damage to proximal tubular cells may contribute to the renal impairment that has been associated with this drug. Our findings underscore the value of monitoring serum aminoglycoside concentrations in children being treated with amphotericin B.