Treatment of Accidental Intrathecal Methotrexate Overdose With Intrathecal Carboxypeptidase G2

Navigating methotrexate toxicity: Examining the therapeutic roles of folinic acid and glucarpidase

Methotrexate (MTX) toxicity varies depending on factors such as dosing frequency (acute or repeated), dosage (low or high) and the administration route (oral, parenteral or intrathecal). Renal impairment can trigger or exacerbate MTX toxicity. Acute oral low-dose MTX (LDMTX) overdoses seldom lead to toxicity due to the saturable maximal bioavailable dose, but toxicity risks increase with repeated low doses (>3 days), high-dose MTX (HDMTX) or intrathecal poisoning. Folinic acid shares MTX transporters in the gut and cells and bypasses the MTX-induced dihydrofolate reductase inhibition. The required folinic acid dosage differs for low-dose and high-dose MTX toxicities. Acute LDMTX poisoning rarely requires folinic acid, while chronic LDMTX poisoning needs low-dose folinic acid until cellular function is restored. In HDMTX toxicities, early intravenous folinic acid administration is recommended, with dose and duration being guided by MTX concentrations and clinical improvement. In intrathecal MTX poisoning, folinic acid should be administered intravenously. Glucarpidase, a recombinant bacterial enzyme, has a high affinity for MTX and folate analogues in the intravascular or intrathecal systems. It decreases serum MTX concentrations by 90%-95% within 15 min. Its primary indication is for intrathecal MTX poisoning. It is rarely indicated in HDMTX toxicity unless patients have renal injury. However, there is no literature evidence supporting its use in HDMTX poisoning. Its use is limited by its significant cost and lack of availability. Haemodialysis can be potentially useful for MTX removal in cases where glucarpidase is not available. Additionally, fluid hydration, renal support and urine alkalinization are important adjunctive therapies for managing MTX toxicities.

Glucarpidase (carboxypeptidase G2): Biotechnological production, clinical application as a methotrexate antidote, and placement in targeted cancer therapy

Patients receiving high-dose methotrexate (HDMTX) for malignancies are exposed to diverse complications, including nephrotoxicity, hepatotoxicity, mucositis, myelotoxicity, neurological symptoms, and death. Glucarpidase is a recombinant carboxypeptidase G2 (CPG2) that converts MTX into nontoxic metabolites. In this study, the role of vector type, gene optimization, orientation, and host on the expression of CPG2 is investigated. The effectiveness of various therapeutic regimens containing glucarpidase is classified and perspectives on the dose adjustment based on precision medicine are provided. Conjugation with cell-penetrating peptides, human serum albumin, and polymers such as PEG and dextran for delivery, higher stability, and production of the biobetter variants of CPG2 is highlighted. Conjugation of CPG2 to F(ab՜)2 or scFv antibody fragments against tumor-specific antigens and the corresponding prodrugs for tumor-targeted drug delivery using the antibody-directed enzyme prodrug therapy (ADEPT) is communicated. Trials to reduce the off-target effects and the possibility of repeated ADEPT cycles by adding pro-domains sensitive to tumor-overexpressed proteases, antiCPG2 antibodies, CPG2 mutants with immune-system-unrecognizable epitopes, and protective polymers are reported. Intracellular cpg2 gene expression by gene-directed enzyme prodrug therapy (GDEPT) and the concerns regarding the safety and transfection efficacy of the GDEPT vectors are described. A novel bifunctional platform using engineered CAR-T cell micropharmacies, known as Synthetic Enzyme-Armed KillER (SEAKER) cells, expressing CPG2 to activate prodrugs at the tumor niche is introduced. Taken together, integrated data in this review and recruiting combinatorial strategies in novel drug delivery systems define the future directions of ADEPT, GDEPT, and SEAKER cell therapy and the placement of CPG2 therein.

Extracorporeal Treatment for Methotrexate Poisoning: Systematic Review and Recommendations from the EXTRIP Workgroup

Methotrexate is used in the treatment of many malignancies, rheumatological diseases, and inflammatory bowel disease. Toxicity from use is associated with severe morbidity and mortality. Rescue treatments include intravenous hydration, folinic acid, and, in some centers, glucarpidase. We conducted systematic reviews of the literature following published EXtracorporeal TReatments In Poisoning (EXTRIP) methods to determine the utility of extracorporeal treatments in the management of methotrexate toxicity. The quality of the evidence and the strength of recommendations (either "strong" or "weak/conditional") were graded according to the GRADE approach. A formal voting process using a modified Delphi method assessed the level of agreement between panelists on the final recommendations. A total of 92 articles met inclusion criteria. Toxicokinetic data were available on 90 patients (89 with impaired kidney function). Methotrexate was considered to be moderately dialyzable by intermittent hemodialysis. Data were available for clinical analysis on 109 patients (high-dose methotrexate [>0.5 g/m2]: 91 patients; low-dose [≤0.5 g/m2]: 18). Overall mortality in these publications was 19.5% and 26.7% in those with high-dose and low-dose methotrexate-related toxicity, respectively. Although one observational study reported lower mortality in patients treated with glucarpidase compared with those treated with hemodialysis, there were important limitations in the study. For patients with severe methotrexate toxicity receiving standard care, the EXTRIP workgroup: (1) suggested against extracorporeal treatments when glucarpidase is not administered; (2) recommended against extracorporeal treatments when glucarpidase is administered; and (3) recommended against extracorporeal treatments instead of administering glucarpidase. The quality of evidence for these recommendations was very low. Rationales for these recommendations included: (1) extracorporeal treatments mainly remove drugs in the intravascular compartment, whereas methotrexate rapidly distributes into cells; (2) extracorporeal treatments remove folinic acid; (3) in rare cases where fast removal of methotrexate is required, glucarpidase will outperform any extracorporeal treatment; and (4) extracorporeal treatments do not appear to reduce the incidence and magnitude of methotrexate toxicity.

Ventriculolumbar perfusion and inhalational anesthesia with sevoflurane in an accidental intrathecal injection of tranexamic acid: unreported treatment options

BACKGROUND

Tranexamic acid (TXA) decreases hemorrhage-related mortality in trauma patients and is increasingly being used during obstetric and orthopedic surgeries. Inadvertent intrathecal injection of TXA is a rare, potentially lethal event leading to dose-dependent cardiotoxicity and neurotoxicity. TXA enhances neuronal excitation by antagonizing inhibitory γ-aminobutyric acid type A and glycine receptors. Until now, mechanistic-based pharmacological treatments targeting multiple central nervous system receptors have been advocated for use in such cases, with no data on intrathecal TXA elimination techniques.

CASE PRESENTATION

A patient scheduled for hip surgery accidentally received 350 mg of intrathecal TXA instead of levobupivacaine. The clinical picture progressed from spinal segmental myoclonus to generalized convulsions and malignant arrhythmias. The treatment consisted of ventriculolumbar perfusion with normal saline at a rate of 50 mL/hour starting 5 hours after TXA administration and inhalational sedation with sevoflurane, in addition to drugs acting on multiple receptors at different central nervous system levels. Over 2 months the neurological status improved, although it was not complete.

CONCLUSIONS

For the first time, the feasibility and possible clinical efficacy of combined treatment with ventriculolumbar perfusion and inhalational sedation with sevoflurane were demonstrated. A referral to a neurosurgical facility is recommended in patients with acute TXA-induced neurotoxicity and cardiotoxicity.

Use of Exogenous Enzymes in Human Therapy: Approved Drugs and Potential Applications

The development of safe and efficacious enzyme-based human therapies has increased greatly in the last decades, thanks to remarkable advances in the understanding of the molecular mechanisms responsible for different diseases, and the characterization of the catalytic activity of relevant exogenous enzymes that may play a remedial effect in the treatment of such pathologies. Several enzyme-based biotherapeutics have been approved by FDA (the U.S. Food and Drug Administration) and EMA (the European Medicines Agency) and many are undergoing clinical trials. Apart from enzyme replacement therapy in human genetic diseases, which is not discussed in this review, approved enzymes for human therapy find applications in several fields, from cancer therapy to thrombolysis and the treatment, e.g., of clotting disorders, cystic fibrosis, lactose intolerance and collagen-based disorders. The majority of therapeutic enzymes are of microbial origin, the most convenient source due to fast, simple and cost-effective production and manipulation. The use of microbial recombinant enzymes has broadened prospects for human therapy but some hurdles such as high immunogenicity, protein instability, short half-life and low substrate affinity, still need to be tackled. Alternative sources of enzymes, with reduced side effects and improved activity, as well as genetic modification of the enzymes and novel delivery systems are constantly searched. Chemical modification strategies, targeted- and/or nanocarrier-mediated delivery, directed evolution and site-specific mutagenesis, fusion proteins generated by genetic manipulation are the most explored tools to reduce toxicity and improve bioavailability and cellular targeting. This review provides a description of exogenous enzymes that are presently employed for the therapeutic management of human diseases with their current FDA/EMA-approved status, along with those already experimented at the clinical level and potential promising candidates.

A Case of Methotrexate Neurotoxicity Presented as Status Epilepticus, Encephalopathy, and High Fever

High-dose methotrexate is used to treat a range of adult and childhood cancers including osteosarcoma. Significant neurotoxicity is reported in 1% to 4.5% of patients treated with high-dose methotrexate and can present in a wide variety of symptoms. We present a case of a 14-year-old boy with a recent diagnosis of osteosarcoma who presented to the emergency department with status epilepticus, altered mental status, and very high fever secondary to methotrexate neurotoxicity. We review current literature and discuss some controversies related to this state. We also describe high fever as one of the possible symptoms associated with this condition and suggest using specific magnetic resonance imaging sequence to uncover abnormal findings related to this state. Since high-dose methotrexate is not a rare treatment in this era, we believe that in addition to oncologists, emergency department and intensive care providers should be aware of the potential role of methotrexate in causing significant neurotoxicity and include it in the differential diagnosis when treating a patient presenting with new neurological symptoms in the setting of recent high-dose methotrexate treatment.

Treatment of two cases on the same day of intrathecal methotrexate overdose using cerebrospinal fluid exchange and intrathecal instillation of carboxypeptidase-G2

BACKGROUND

Two 14-year old boys with acute lymphocytic leukemia were treated according to the NOPHO-ALL-08 protocol with intrathecal methotrexate (MTX) on the same day. Due to a preparation error in the hospital pharmacy, they were both given 240 mg of MTX instead of the prescribed 12 mg. Treatment (or methods): Both patients developed acute neurotoxicity with confusion, pain and seizures. Intravenous dexamethasone and folinic acid (leucovorin) was given. Exchange of cerebrospinal fluid was performed. Intrathecal glucarpidase (carboxypeptidase-G2) was administered after 11 h.

RESULTS

One patient developed a toxic arachnoiditis. Three years after the incident, one patient has no neurological or neuropsychological sequelae after the overdose, while the other reports some loss of short-term memory.

CONCLUSION

Fast recognition and treatment of intrathecal MTX overdose is critical to survival and outcome. Efforts to prevent such overdoses are of vital importance.

Consensus Guideline for Use of Glucarpidase in Patients with High-Dose Methotrexate Induced Acute Kidney Injury and Delayed Methotrexate Clearance

An expert panel was convened to provide specific, expert consensus guidelines for the use of glucarpidase in patients who develop high‐dose methotrexate (HDMTX)‐induced nephrotoxicity and delayed methotrexate excretion. This guideline provides recommendations to identify the population of patients who would benefit from glucarpidase rescue by more precisely defining the absolute methotrexate concentrations associated with risk for severe or life‐threatening toxicity at several time points after the start of a HDMTX infusion.

Acute kidney injury due to high‐dose methotrexate (HDMTX) is a serious, life‐threatening toxicity that can occur in pediatric and adult patients. Glucarpidase is a treatment approved by the Food and Drug Administration for high methotrexate concentrations in the context of kidney dysfunction, but the guidelines for when to use it are unclear. An expert panel was convened to provide specific, expert consensus guidelines for the use of glucarpidase in patients who develop HDMTX‐induced nephrotoxicity and delayed methotrexate excretion. The guideline provides recommendations to identify the population of patients who would benefit from glucarpidase rescue by more precisely defining the absolute methotrexate concentrations associated with risk for severe or life‐threatening toxicity at several time points after the start of an HDMTX infusion. For an HDMTX infusion ≤24 hours, if the 36‐hour concentration is above 30 µM, 42‐hour concentration is above 10 µM, or 48‐hour concentration is above 5 µM and the serum creatinine is significantly elevated relative to the baseline measurement (indicative of HDMTX‐induced acute kidney injury), glucarpidase may be indicated. After a 36‐ to 42‐hour HDMTX infusion, glucarpidase may be indicated when the 48‐hour methotrexate concentration is above 5 µM. Administration of glucarpidase should optimally occur within 48–60 hours from the start of the HDMTX infusion, because life‐threatening toxicities may not be preventable beyond this time point.

Implications for Practice.

Glucarpidase is a rarely used medication that is less effective when given after more than 60 hours of exposure to high‐dose methotrexate, so predicting early which patients will need it is imperative. There are no currently available consensus guidelines for the use of this medication. The indication on the label does not give specific methotrexate concentrations above which it should be used. An international group of experts was convened to develop a consensus guideline that was specific and evidence‐based to identify the population of patients who would benefit from glucarpidase.

Intracerebroventricular drug administration

Among the various routes of drug administration, perhaps the least studied is intracerebroventricular (ICV) administration. This route has been shown to be particularly useful in administering to the central nervous system (CNS) drugs that do not cross the blood-brain barrier readily. As such, the ICV route is a valuable option for providing therapeutic CNS drug concentrations to treat patients with CNS infectious and neoplastic diseases. This route of drug administration also has the advantage of minimizing systemic toxicity.

Implications of Intrathecal Chemotherapy for Anaesthesiologists: A Brief Review

Intrathecal chemotherapy is routinely prescribed in medical oncology practice, either for prophylaxis or for treatment of leptomeningeal disease due to a primary haematological disease or a metastatic disease due to any other malignancy. As these groups of patients are coagulopathic either because of the disease per se or due to systemic chemotherapy, lumbar puncture in them is considered challenging and is expected to be performed by an anaesthesiologist because of their expertise in this procedure. However, the challenge is not only in performing the lumbar puncture safely but also in dealing with other issues like explaining and handling complications that can happen either due to the drug injected intrathecally or due to a neurodeficit occurring either due to the underlying coagulopathy or due to the progression of leptomeningeal disease.

Intrathecal chemotherapy: potential for medication error

BACKGROUND

The central nervous system is a unique sanctuary site for malignant disease. To ensure optimal disease control, intrathecal (IT) chemotherapy is commonly given in conjunction with standard chemotherapy protocols, thus providing the opportunity for medication errors.

OBJECTIVE

A systematic review of the current literature on medication errors associated with the administration of IT chemotherapy was conducted.

METHODS

English-language literature published from January 1960 through June 2013 was accessed. Case reports, clinical studies, and review articles pertaining to IT medication errors were included in the review. References of all relevant articles were searched for additional citations.

RESULTS

Twenty-two cases of accidental IT overdoses have been reported with methotrexate and 1 with cytarabine. There have been numerous cases of antineoplastic agents intended for administration by the parenteral route being inadvertently given intrathecally. Vincristine has been implicated 31 times (25 deaths), as well as vindesine, asparaginase, bortezomib, daunorubicin, and dactinomycin. This has led to profound toxicity and, commonly, death. Unfortunately, many cases go unrecognized or unreported.

CONCLUSIONS

The best method for eliminating the risk of IT medication errors is to develop effective methods of prevention and incorporate them into oncology and hematology practice internationally. Strategies include abolishing the syringe as a method of vinca alkaloid administration and substituting small-volume intravenous bags, and developing novel methods for intraspinal drug administration.

IMPLICATIONS FOR PRACTICE

The nursing profession is in a unique position to influence change and lead the way in establishing preventative strategies into current practice.

Antidotes to coumarins, isoniazid, methotrexate and thyroxine, toxins that work via metabolic processes

Some toxins cause their effects by affecting physiological processes that are fundamental to cell function or cause systemic effects as a result of cellular interaction. This review focuses on four examples, coumarin anticoagulants, isoniazid, methotrexate and thyroxine from the context of management of overdose as seen in acute general hospitals. The current basic clinical pharmacology of the toxin, the clinical features in overdose and evidence base for specific antidotes are discussed. The treatment for this group is based on an understanding of the toxic mechanism, but studies to determine the optimum dose of antidote are still required in all these toxins except thyroxine, where treatment dose is based on symptoms resulting from the overdose.

Safety of inadvertent administration of overdose of intrathecal Cytarabine in a pediatric patient

PURPOSE

To describe a medication error of intrathecal Cytarabine overdose that was managed conservatively with no apparent toxicities.

SUMMARY

An 11-year-old girl was diagnosed with bone marrow relapsed precursor B-cell acute lymphoblastic leukemia. According to her chemotherapy protocol, she was started on triple intrathecal chemotherapy consisting of Methotrexate, Cytarabine and Hydrocortisone on day 1 of the protocol. After the intrathecal therapy being administered to the patient, the pharmacist who checked the medication realized that the wrong formulation of Cytarabine was used to prepare the intrathecal therapy; this error resulted in five times overdose of Cytarabine. The patient was then managed conservatively without cerebrospinal fluid exchange. Our patient remained clinically and neurologically stable without apparent toxicities and was discharged safely from hospital.

CONCLUSION

Supportive care without the need for invasive procedures such as cerebrospinal fluid exchange may be adequate for managing intrathecal Cytarabine overdose.

Available extracorporeal treatments for poisoning: overview and limitations

Poisoning is a significant public health problem. In severe cases, extracorporeal treatments (ECTRs) may be required to prevent or reverse major toxicity. Available ECTRs include intermittent hemodialysis, sustained low-efficiency dialysis, intermittent hemofiltration and hemodiafiltration, continuous renal replacement therapy, hemoperfusion, therapeutic plasma exchange, exchange transfusion, peritoneal dialysis, albumin dialysis, cerebrospinal fluid exchange, and extracorporeal life support. The aim of this article was to provide an overview of the technical aspects, as well as the potential indications and limitations of the different ECTRs used for poisoned patients.

Accidental overdose of intrathecal cytarabine in children

OBJECTIVE

To report 2 cases of intrathecal cytarabine overdose in children with cancer, neither of whom underwent cerebrospinal fluid (CSF) exchange per current recommendations or developed apparent toxicity related to the event.

CASE SUMMARY

A 17-year-old female with newly diagnosed acute myeloid leukemia received 177 mg of intrathecal cytarabine rather than the appropriate dose of 70 mg. She was monitored closely with no apparent toxicity from the event. A 4-year-old boy with newly diagnosed precursor B-cell acute lymphoblastic leukemia received 175 mg of intrathecal cytarabine rather than the appropriate dose of 70 mg. CSF was immediately withdrawn and intrathecal hydrocortisone was instilled for possible antiinflammatory effect. He developed no apparent toxicity from the event.

DISCUSSION

Cytarabine is an important chemotherapeutic agent in the treatment of leukemia. One case report of intrathecal cytarabine overdose was identified in the literature, which recommended CSF exchange as management. Neither child in our report underwent CSF exchange or developed apparent toxicity related to the event. Institutional changes were made in both cases to prevent similar events.

CONCLUSIONS

These cases demonstrate that measures such as CSF exchange are not uniformly required for cytarabine overdose.

Glucarpidase to combat toxic levels of methotrexate in patients

In January 2012, glucarpidase (Voraxaze^®) received approval from the US Food and Drug Administration for intravenous treatment of toxic plasma methotrexate concentrations due to impaired renal clearance. Methotrexate, an antifolate agent, has been used for over 60 years in the treatment of various cancers. High-dose methotrexate has been particularly useful in the treatment of leukemias and lymphomas. However, even with aggressive hydration and urine alkalinization, such regimens can lead to acute renal dysfunction, as indicated by decreases in urine production and concomitant increases in blood urea nitrogen and serum creatinine levels. Because methotrexate is largely excreted by the kidneys, this can greatly potentiate tissue damage. Toxic levels of blood methotrexate can be rapidly and effectively decreased by intravenous administration of glucarpidase. Glucarpidase is a recombinant form of carboxypeptidase G2, a bacterial enzyme that rapidly cleaves methotrexate to form the amino acid glutamate and 2,4-diamino-N¹⁰-methylpteroic acid. Catabolites of methotrexate are much less toxic than the parent compound, and are primarily excreted by hepatic mechanisms. Glucarpidase has been available on a compassionate basis since the 1990s, and a variety of case reports and larger clinical trials have demonstrated the safety and efficacy of this drug in patients ranging in age from infants to the elderly and in a variety of races and ethnic groups. Glucarpidase should not be administered within 2 hours of leucovorin, because this agent is a reduced folate which competes with methotrexate for the enzyme and glucarpidase inactivates leucovorin. Side effects of glucarpidase are rare and relatively mild, and include paraesthesia, flushing, nausea, vomiting, pruritus, and headache. Glucarpidase has seen limited use in intrathecal treatment of methotrexate toxicity for which it is also effective. Future applications of this enzyme in chemotherapy continue to be an active area of research.

Glucarpidase

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. Subscribers to The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X.). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X. A drug class review is now published monthly with The Formulary Monograph Service. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The June 2012 monograph topics are on peginesatide, mitomycin for solution, lucinactant, mifepristone, and perampanel. The DUE/MUE is on peginesatide.

Resumption of high-dose methotrexate after acute kidney injury and glucarpidase use in pediatric oncology patients

BACKGROUND

High-dose methotrexate (HDMTX)-induced acute kidney injury is a rare but life-threatening complication. The methotrexate rescue agent glucarpidase rapidly hydrolyzes methotrexate to inactive metabolites. The authors retrospectively reviewed glucarpidase use in pediatric cancer patients at their institution and evaluated whether subsequent resumption of HDMTX was tolerated.

METHODS

Clinical data and outcomes of all patients who received glucarpidase after HDMTX administration were reviewed.

RESULTS

Of 1141 patients who received 4909 courses of HDMTX, 20 patients (1.8% of patients, 0.4% of courses) received 22 doses of glucarpidase. The median glucarpidase dose was 51.6 U/kg (range, 13-65.6 U/kg). At the time of administration, the median plasma methotrexate concentration was 29.1 μM (range, 1.3-590.6 μM). Thirteen of the 20 patients received a total of 39 courses of HDMTX therapy after glucarpidase. The median time to complete methotrexate excretion was 355 hours (range, 244-763 hours) for the HDMTX course during which glucarpidase was administered, 90 hours (range, 66-268 hours) for the next HDMTX course, and 72 hours (range, 42-116 hours) for subsequent courses. The median peak serum creatinine level during these HDMTX courses was 2.2 mg/dL (range, 0.8-9.6 mg/dL), 0.8 mg/dL (range, 0.4-1.6 mg/dL), and 0.6 mg/dL (range, 0.4-0.9 mg/dL), respectively. One patient experienced nephrotoxicity upon rechallenge with HDMTX. Renal function eventually returned to baseline in all patients, and no patient died as a result of methotrexate toxicity.

CONCLUSIONS

The current results indicated that it is possible to safely resume HDMTX therapy after glucarpidase treatment for HDMTX-induced acute kidney injury.

Glucarpidase, leucovorin, and thymidine for high-dose methotrexate-induced renal dysfunction: clinical and pharmacologic factors affecting outcome

PURPOSE

To assess the role of the recombinant bacterial enzyme, glucarpidase (carboxypeptidase-G(2)), leucovorin, and thymidine in the management and outcome of patients with high-dose methotrexate (HDMTX) -induced nephrotoxicity.

METHODS

Patients with HDMTX-induced nephrotoxicity received one to three doses of intravenous (IV) glucarpidase and leucovorin rescue. The initial cohort (n = 35) also received thymidine by continuous IV infusion. Subsequently, thymidine was restricted to patients with prolonged exposure (> 96 hours) to methotrexate (MTX) or with substantial MTX toxicity at study entry. Plasma MTX, leucovorin, and 5-methyltetrahydrofolate (5-mTHF) concentrations were measured pre- and postglucarpidase. Toxicities were monitored, and logistic regression analysis was used to assess the relationship of baseline characteristics to the development of severe toxicity and death.

RESULTS

Glucarpidase was administered at a median of 96 hours (receiving thymidine, n = 44) and 66 hours (not receiving thymidine, n = 56) after the start of the MTX infusion. Plasma MTX concentrations decreased within 15 minutes of glucarpidase by 98.7%. Plasma 5-mTHF concentrations also decreased more than 98% after administration of glucarpidase. Of 12 deaths, six were directly attributed to irreversible MTX toxicity. Presence of grade 4 toxicity before administration of glucarpidase, inadequate initial increase in leucovorin dosing, and administration of glucarpidase more than 96 hours after the start of the MTX infusion were associated with development of grade 4 and 5 toxicity.

CONCLUSION

Early intervention with the combination of leucovorin and glucarpidase is highly effective in patients who develop HDMTX-induced renal dysfunction. Severe toxicity and mortality occurred in patients in whom glucarpidase rescue was delayed and occurred despite thymidine administration.

Drugs and pharmaceuticals: management of intoxication and antidotes

The treatment of patients poisoned with drugs and pharmaceuticals can be quite challenging. Diverse exposure circumstances, varied clinical presentations, unique patient-specific factors, and inconsistent diagnostic and therapeutic infrastructure support, coupled with relatively few definitive antidotes, may complicate evaluation and management. The historical approach to poisoned patients (patient arousal, toxin elimination, and toxin identification) has given way to rigorous attention to the fundamental aspects of basic life support--airway management, oxygenation and ventilation, circulatory competence, thermoregulation, and substrate availability. Selected patients may benefit from methods to alter toxin pharmacokinetics to minimize systemic, target organ, or tissue compartment exposure (either by decreasing absorption or increasing elimination). These may include syrup of ipecac, orogastric lavage, activated single- or multi-dose charcoal, whole bowel irrigation, endoscopy and surgery, urinary alkalinization, saline diuresis, or extracorporeal methods (hemodialysis, charcoal hemoperfusion, continuous venovenous hemofiltration, and exchange transfusion). Pharmaceutical adjuncts and antidotes may be useful in toxicant-induced hyperthermias. In the context of analgesic, anti-inflammatory, anticholinergic, anticonvulsant, antihyperglycemic, antimicrobial, antineoplastic, cardiovascular, opioid, or sedative-hypnotic agents overdose, N-acetylcysteine, physostigmine, L-carnitine, dextrose, octreotide, pyridoxine, dexrazoxane, leucovorin, glucarpidase, atropine, calcium, digoxin-specific antibody fragments, glucagon, high-dose insulin euglycemia therapy, lipid emulsion, magnesium, sodium bicarbonate, naloxone, and flumazenil are specifically reviewed. In summary, patients generally benefit from aggressive support of vital functions, careful history and physical examination, specific laboratory analyses, a thoughtful consideration of the risks and benefits of decontamination and enhanced elimination, and the use of specific antidotes where warranted. Data supporting antidotes effectiveness vary considerably. Clinicians are encouraged to utilize consultation with regional poison centers or those with toxicology training to assist with diagnosis, management, and administration of antidotes, particularly in unfamiliar cases.

Delayed recognition of intrathecal methotrexate overdose

A 10-year-old girl who presented to our hospital was diagnosed as having B-precursor cell acute lymphoblastic leukemia. St Jude's Total XIII protocol was started. In the second block of the consolidation phase, 10 hours after triple intrathecal treatment, we realized that instead of 12 mg, 120 mg of methotrexate had accidentally been given. Although the patient had no symptoms 10 hours after intrathecal treatment, to prevent the possible neurotoxic effects of methotrexate, a cerebrospinal fluid exchange was performed. Simultaneously, systemic dexamethasone and calcium folinic acid were given. At the time of this writing (2 y), the patient has had no symptoms and has continued on the chemotherapy protocol as planned. Administration of high-dose intrathecal methotrexate may not lead to symptoms, as was the case in our patient. This may be related to individual variations in cerebrospinal fluid dynamics and drug metabolism.

Spinal muscular atrophy

Spinal muscular atrophy (SMA) is a potentially devastating and lethal neuromuscular disease frequently manifesting in infancy and childhood. The discovery of the underlying mutation in the survival of motor neurons 1 (SMN1) gene has accelerated preclinical research, leading to treatment targets and transgenic mouse models, but there is still no effective treatment. The clinical severity is inversely related to the copy number of SMN2, a modifying gene producing some full-length SMN transcript. Drugs shown to increase SMN2 function in vitro, therefore, have the potential to benefit patients with SMA. Because several drugs are now on the horizon of clinical investigation, we review recent clinical trials for SMA and discuss the challenges and opportunities associated with SMA drug development. Although an orphan disease, SMA is well-positioned for successful trials given that it has a common genetic etiology in most cases, that it can be readily diagnosed, that preclinical research in vitro and in transgenic animals has identified candidate compounds, and that trial networks have been established.

Central nervous system toxicity from cancer therapies

The central nervous system (CNS) is an organ with a unique profile of vulnerability to antineoplastic treatments. In many cases, CNS neurotoxicity is the dose-limiting side effect of treatment for systemic and CNS neoplasms. Novel methods of delivering radiation and chemotherapy agents have led to recognition of new forms of CNS neurotoxicity. In this article, the authors review the most important CNS toxicities of cancer treatment.