Joseph D. Borsi

A comparative study on the pharmacokinetics of methotrexate in a dose range of 0.5 g to 33.6 g/m2 in children with acute lymphoblastic leukemia

Concentrations of methotrexate have been determined in the serum and cerebrospinal fluid after 406 infusions of methotrexate to 58 children with acute lymphoblastic leukemia. The dose of methotrexate varied between 500 mg/m2 and 33 600 mg/m2. Pharmacokinetic analysis of the data has been carried out. The effect of dose, age, and number of treatments on steady‐state concentration, serum half‐life, cerebrospinal fluid (CSF) serum distribution ratio, volume of distribution, systemic clearance of methotrexate was examined. The elevation of dose resulted in a nonproportional increase of the steady‐state concentrations both in serum and CSF. The great inpatient and interpatient variations of steady‐state concentrations caused only statistically not significant differences in the parameters of different subgroups of dosages. Correlation was found between concentrations of methotrexate in serum and CSF. One to 4 years old children were found to have lower steady‐state concentrations of methotrexate in the serum and CSF, greater volume of distribution and faster clearence of the drug. Dose‐dependency and age‐dependency of methotrexate pharmacokinetics has been concluded.

Systemic clearance of methotrexate in the prognosis of acute lymphoblastic leukemia in children

The prognostic value of systemic clearance of methotrexate (MTX) has been evaluated in 58 children with acute lymphoblastic leukemia, receiving altogether 380 MTX infusions in a dose range of 0.5 to 33.6 g/m2. The linear regression analysis of dose‐steady state concentration relationship revealed that relapsed children had significantly lower steady state concentration of MTX (faster systemic clearance) than those who remained in continuous complete remission (CCR), whatever dosage of the drug was given. Relapsed children (n = 25) had a systemic clearance of MTX 122.5 ± 55.5 ml/minute/m2 versus 71.8 ± 25.8 ml/minute/m2 found in the CCR patients (n = 33) when the dosage of MTX was 0.5 to 1.0 g/m2. When the dose was 6.0 to 8.0 g/m2 the clearance values were 93.27 ± 32.6 versus 61.8 ± 24.5 ml/minute/m2, respectively. The differences are statistically significant (P < 0.001). In 16 of 25 relapsed patients (64%) an increase of the systemic clearance has been observed during the consecutive treatments, but only 4/33 CCR patients (12%) has expressed such a phenomenon. The dose‐independent prognostic relevance of systemic clearance of MTX as a possible sign of resistance to MTX is concluded.

How much is too much? Folinic acid rescue dose in children with acute lymphoblastic leukaemia

The effect of folinic acid rescue dose on the event-free survival of 71 children with acute lymphoblastic leukaemia was examined in a retrospective clinical study. All patients, diagnosed between 1 January 1980 and 1 January 1989, were treated according to the Norwegian Pilot protocol which included eight courses of high dose (6-8 g/m2/24 h intravenous infusion) methotrexate. Following the infusion, a uniform dose of 75 mg (at 36 h after the beginning of the drug infusion) and 15 mg (at 39-106 h) folinic acid rescue was administered to all patients, at predetermined intervals. The uniformity of the rescue dose resulted in distribution of dosages in the range of 38-140 mg/m2 and 7.5-28 mg/m2 for the different periods, respectively, when the dose was recalculated on the basis of the body surface area of the individual patients. The event-free survival of children receiving less or more than 15 mg/m2 (75 mg/m2) rescue dose was compared. Although no significant difference was found, a tendency was observed for a lower risk of relapse in patients receiving less folinic acid. No major methotrexate-related toxicity was observed in the group of patients receiving the lower dose of rescue. These observations suggest that the reduction of folinic acid rescue dose below the generally accepted 12-15 mg/m2 dose may increase the efficacy of high-dose methotrexate therapy while still remaining safe in preventing treatment-related toxicity. Prospective, randomised clinical trials are needed to examine the role of rescue as a determinant of effective exposure to methotrexate in patients receiving high-dose methotrexate treatment.

Rescue after Intermediate and High-Dose Methotrexate: Background, Rationale, and Current Practice

Pharmacologic rescue methods used in combination with intermediate and high-dose methotrexate therapy are reviewed, with special emphasis on rescue with nucleosides and folinic acid. The mechanism of action, pharmacokinetics, and clinical applications of the rescue agents are described in detail in view of the literature and also of the own findings of the authors. In spite of the promising results of the in vitro studies and in vivo experiments in animal models, the clinical value of thymidine as a rescue agent remains to be determined. Currently, the only indication to use thymidine instead of folinic acid following high-dose methotrexate is to prevent toxicity related to extremely high methotrexate levels in patients with delayed elimination of methotrexate. In spite of the widespread application of folinic acid rescue, the exact mechanism of its action is not fully understood. The rescue dose and schedule in the majority of clinical protocols is empirical, and the start of the rescue administration is too early, allowing less than 36 to 42 hours of exposure to methotrexate. Clinical and laboratory findings indicate that while the early start of FA administration is unnecessary for protecting normal cells, it is potentially dangerous in terms of reduction of the antitumor effect of methotrexate. Our findings suggest that less than the most widely used 12-15 mg/m2 per dose rescue may be sufficient in preventing methotrexate related toxicity in patients with normal elimination of the drug. In addition, reducing the dose of the rescue may be beneficial to achieve better therapeutic results with high-dose methotrexate. Due to methodological problems, the pharmacokinetics of folinic acid rescue has not been excessively studied in humans. Recent data indicate that the pharmacokinetics of folinic acid in children is characterized by great intra- and interpatient variability. The effect of food on the bioavailability of folinic acid has not yet been studied, though it is most frequently administered orally. The introduction of the pure l-stereoisomer of the rescue agent in the clinical practice may eliminate potential interactions with the d-isomer, and may also simplify the introduction of therapeutic drug monitoring for folinic acid as well. This could lead to more rational clinical use of folinic acid as a rescue agent following intermediate and high-dose methotrexate therapy.

Evaluation of Serious Adverse Events in Patients Treated with Protocols Including Methotrexate Infusions

During the period 1979 to 1992 we treated 141 children for various malignant diseases with protocols including methotrexate (MTX) infusions in doses ranging from 0.5 to 33.6 g/m2. During a total of 922 courses, there were no fatal complications associated with MTX treatment. Serum MTX concentration and pharmacokinetic data were monitored continuously during the infusions. In this study, we evaluated the occurrence of serious untoward reactions to MTX infusions. Impaired renal function with delayed drug elimination was seen in seven patients, all boys, especially after short infusion times. All recovered completely without any serious clinical symptoms. In three leukemia patients who later died from resistant disease, we observed late neurological disturbances and computer tomography (CT) brain scan abnormalities. Pharmacokinetic data from the patients with complications are described and confirm that serial MTX concentration monitoring is the most important early indicator of renal toxicity.

Prognostic importance of systemic clearance of methotrexate in childhood acute lymphoblastic leukemia

SummaryPharmacokinetic studies of methotrexate have been carried out in 21 children with acute lymphoblastic leukemia diagnosed in 1981. Children were treated with intermediate dose (500 mg/m2) methotrexate in keeping with the 1981 ALL treatment Protocol of the Hungarian Childhood Leukemia Working Group. Of the 21 children, 8 relapsed, and 13 are in continuous complete remission. In the relapsed patients significantly increased systemic clearance of methotrexate was observed at the time of the second methotrexate treatment cycle compared with the calculated value after the first administration of the drug. No such change in the clearance was found in patients who are still in remission. There was no difference between children who relapsed or who are in remission in the elimination half-time of the drug. Age, sex, WBC at diagnosis, and systemic clearance of methotrexate were found to be connected with the probability of relapse in the patients studied. The possible reasons for the prognostic role of systemic methotrexate clearance are discussed.

ADMINISTRATION OF ETHYOL (AMIFOSTINE) TO A CHILD WITH MEDULLOBLASTOMA TO AMELIORATE HEMATOLOGICAL TOXICITY OF HIGH DOSE CARBOPLATIN

The first report on the administration of the chemoprotective agent Ethyol (amifostine) in conjunction with high dose carboplatin to a patient in the pediatric/adolescent age group is presented. A 17 year old teenager with recurrent cerebellar medulloblastoma received a total of five courses of high dose carboplatin 2 x 600 mg/m2 (1200 mg/m2 total) in each cycle. A complete response has been observed following the third treatment cycle. However, cumulative grade IV hematological toxicity developed following each of the first four treatments. Therefore, the fifth treatment was administered in conjunction with amifostine, at a dose of 2 x 740 mg/m2. Time to complete hematological recovery (Hb > 100 g/l, granulocytes > 2.0 G/l, platelets > 100 G/l) was 52, 58, 72, 78 and 50 days, respectively, following treatments nos 1, 2,,3, 4 and 5. The duration of grade III-IV neutropenia (< 1.0 G/l) was 3, 7, 8, 10 and 5 days, respectively. The duration of grade II-IV thrombocytopenia (platelets < 75 G/l) was 10, 25, 35, 40 and 32 days, respectively. Grade IV thrombocytopenia (platelets < 25 G/l) lasted for 5, 10, 12, 18 and 3 days, respectively, after each consecutive treatment. The total number of platelet transfusions was 1, 2, 2, 3 and 1, with the transfusion of 6, 9, 11, 11 and 5 units of platelets. The administration of amifostine has not been accompanied by any serious side effect. A short decrease in body temperature and a transient drop of blood pressure have been observed. Although hematological toxicity of high dose carboplatin has not been eliminated by amifostine, we conclude that significant protection was achieved in this situation of progressive bone marrow exhaustion.

Pharmacokinetics and metabolism of methotrexate : an example for the use of clinical pharmacology in pediatric oncology

Article de synthese concernant la pharmacocinetique clinique du methrotrexate. Selon la voie dadministration choisie, la distribution tissulaire du medicament differe. Les auteurs font le point sur les valeurs cinetiques obtenues au niveau du systeme nerveux central, du systeme osteoarticulaire et des erythrocytes, avant de resumer les connaissances acquises sur le metabolisme et lelimination du methotrexate

7-Hydroxymethotrexate concentrations in serum and cerebrospinal fluid of children with acute lymphoblastic leukemia.

SummaryConcentrations of methotrexate (MTX) and 7-hydroxymethotrexate (7-OH-MTX) were determinded by HPLC in the serum and cerebrospinal fluid (CSF) of 29 children with acute lymphoblastic leukemia. CSF and serum samples were obtained at the end of 104 infusions of MTX given in a dose range of 0.5–8.0 g/m2. Concentrations, distribution ratios in serum and CSF for MTX and 7-OH-MTX, and the metabolic index were analyzed with regard to the MTX dose, age and clinical state of the patients. A wide inter-patient (2- to 12-fold) but narrower (1,1- to 3,5-fold) intra-patient variability of the concentrations was observed. A dose-proportional increase in the metabolite concentration was found in serum. On the other hand, the elevation of the level of metabolite in CSF was less than porportional to the dose. The CSF/serum distribution data suggest the existence of a saturable carrier system for MTX and 7-OH-MTX between serum and CSF that has lower affinity for 7-OH-MTX. No correlation was found between concentrations of MTX and 7-OH-MTX in the serum of patients receiving the same dose of MTX. No significant difference was observed in the values for metabolic index between relapsed patients and those who were in continuous complete remission. A significant correlation was found between age and metabolic index: the younger the patient, the higher the metabolite concentration measured in serum.

Methotrexate administered by 6-h and 24-h infusion: a pharmacokinetic comparison.

SummaryThe pharmacokinetics of 8 g/m2 methotrexate (MTX) was compared following short (6 h) and long (24 h) infusions of the drug to 11 children with osteogenic sarcoma (OS; 42 infusion) and 28 children with acute lymphoblastic leukemia (ALL: 118 infusions), respectively. No difference was observed in the first-phase half-life, in systemic clearance or in the volume of distribution of the drug (P>0.05). The concentration of MTX at the end of the infusion was ∼4-fold higher when the drug was given over only 6 h. However, patients receiving 24-h infusions had ∼9-fold higher levels by 24 h after the beginning of the infusion. The area under the data curve from start of the MTX infusion until the beginning of folinic acid rescue administration was significantly higher in patients with osteogenic sarcoma (6-h infusions), while the area under the log-data curve was significantly longer in the ALL group (24-h infusions) for the same period. The latter parameter is considered to be characteristic for the concentration-time-effect relationship. The longer duration of MTX administration (with delayed rescue) is thought to be more beneficial from the pharmacokinetic aspect. Patients with osteogenic sarcoma had significantly lower concentrations of MTX at the end of their last treatment with MTX than at the end of the first infusion. Patients developing MTX toxicity had shorter half-lives of MTX in the beta phase. It is suggested that cisplatin induced tubular loss of MTX and folinic acid is responsible for these observations. A wider application of clinical pharmacologic findings in the practice of the administration of cytostatics is indicated.