Current pharmacological treatment approaches to central nervous system leukaemia.

Significant advances in the treatment and prevention of meningeal leukaemia have been made in the past 3 decades. This progress has resulted from the development of innovative approaches to treatment as well as a better understanding of the pharmacokinetics and pharmacodynamics of the commonly used antileukaemic agents. Intrathecal therapy, via the intralumbar or intraventricular route, is a form of regional therapy that results in the delivery of very high drug concentrations to the principle target tumour site (the meninges) using a relatively small drug dose, thereby minimising both systemic drug exposure and systemic toxicity. The dosage and schedules, clinical pharmacology and toxicities of the commonly used intrathecal agents, methotrexate and cytarabine (cytosine arabinoside; Ara-C) are discussed in detail. Another approach which has been used to overcome the poor penetration of antileukaemic drugs into the CNS has been the use of high-dose systemic therapy. This strategy has been successfully applied in the treatment of meningeal leukaemia using both high-dose methotrexate and high-dose cytarabine. The clinical pharmacology, toxicities, and potential limitations of this approach are outlined. Finally, new agents that are currently undergoing clinical evaluation and future directions for research are also discussed.     

Pharmacologic strategies for the treatment of meningeal malignancy

Summary There have been significant strides in the treatment and prevention of meningeal cancer, particularly meningeal leukemia, during the past thirty years. These advantages are a direct result of innovative therapeutic approaches specifically designed to overcome the limitations of systemically administered chemotherapy. Such approaches include the administration of intrathecal chemotherapy by intralumbar or intraventricular injection, the administration of very high-dose systemic chemotherapy, and the administration of cranial or craniospinal irradiation. A better understanding of the central nervous system pharmacokinetics of commonly used anticancer agents has also resulted in improvements in the treatment of meningeal cancer. In this article, the clinical pharmacology of the most commonly used intrathecal agents and pharmacologic strategies for the treatment of meningeal cancer will be discussed. In addition, an overview of new agents for intrathecal administration and other novel CNS targeted therapies will be presented. Address for offprints: Susan M. Blaney, Texas Children's Cancer Center, 6621 Fannin, MC 3-3320, Houston, TX 77030, USA     

Pharmacokinetics of nimustine, cytosine arabinoside, and methotrexate in cerebrospinal fluid during cerebrospinal fluid perfusion chemotherapy

This report investigates the pharmacokinetics of nimustine (ACNU), cytosine arabinoside (Ara-C), and methotrexate (MTX) in cerebrospinal fluid (CSF) during CSF perfusion chemotherapy. A 47-year-old Japanese man with spinal cord, cerebellum and brain stem dissemination of oligo-astrocytoma received nine courses of CSF perfusion chemotherapy with ACNU, Ara-C, and MTX. A CSF perfusion chemotherapy solution was perfused via an Ommaya reservoir in the ventricle, and was discharged by drainage though another Ommaya reservoir in the lumbar spinal canal. CSF samples via Ommaya reservoirs in the lumbar spinal canal were obtained during the fifth and eighth courses of treatment. The concentrations of ACNU and Ara-C in CSF were measured by HPLC, and the MTX concentrations by fluorescence polarization immunoassay. In the fifth course of treatment, a CSF injection chemotherapy solution, consisting of 5 mg of ACNU dissolved in 20 ml of artificial CSF, was injected over a few minutes using the Ommaya reservoir. Next, a CSF perfusion chemotherapy solution, consisting of 10 mg of Ara-C and 5 mg of MTX dissolved in 100 ml of artificial CSF, was perfused over 2 h. In the eighth course of treatment, a CSF perfusion chemotherapy solution, consisting of 5 mg of ACNU, 10 mg of Ara-C and 5 mg of MTX dissolved in 100 ml of artificial CSF, was perfused over 2 h. In both treatments, the highest concentrations of Ara-C and MTX in CSF were observed 1 or 2 h after the end of perfusion, with the values of each drug being similar. The CSF AUCs of Ara-C and MTX in each treatment were of similar values. Although the highest concentration of ACNU in CSF was observed in the fifth treatment 1 h after injection (an injection chemotherapy of ACNU plus a perfusion chemotherapy of Ara-C and MTX), the concentration of ACNU in CSF was undetectable in the eighth treatment (a perfusion chemotherapy of ACNU, Ara-C and MTX). We were successful in administering all anticancer drugs, and reaching a level of over 1.0 microg/ml concentration in CSF of the lumbar spinal canal, using an injection chemotherapy of ACNU plus a perfusion chemotherapy of Ara-C and MTX; this was done even though the drugs, in particular ACNU, underwent some perfusion-period dependent decomposition.     

Pharmacotherapy of primary CNS lymphoma

Primary CNS lymphoma (PCNSL) is distinguished from other brain tumours by its striking response to chemotherapy. Surgery has little role (if any) in the treatment of PCNSL. Radiation therapy has been proven to prolong survival but its use is complicated by delayed neurological toxicity, particularly among the elderly. Progress in understanding the physiology of the blood-brain barrier (BBB) and the pharmacology of chemotherapeutic agents has substantially improved the treatment and prognosis of this disease. The single most effective agent is methotrexate (MTX). The goal of delivering an adequate dose of MTX to the brain and the cerebrospinal fluid (CSF) has been achieved by a variety of strategies, including systemic high dose, intra-arterial injection following pharmacological disruption of the BBB and intrathecal (it.) administration. MTX-based combination chemotherapy has yielded the best results to date but the prognosis of patients with PCNSL remains significantly worse than comparable patients with systemic non-Hodgkin’s lymphoma (NHL). Ongoing trials continue to test novel combinations of agents, doses and improved routes of delivery with the hope of improving disease control and diminishing treatment-related neurotoxicity.     

Pharmacokinetics following intraventricular administration of chemotherapy in patients with neoplastic meningitis

Intraventricular administration of chemotherapy is one approach to overcoming the limited distribution of anticancer drugs and their active metabolites into the CNS. This form of regional chemotherapy has led to effective treatment of occult and overt meningeal leukaemia in humans. In contrast, the efficacy of this therapy is extremely limited in the treatment of leptomeningeal dissemination of various solid tumours. Pharmacokinetic studies of the commonly intraventricularly applied anticancer agents in humans have demonstrated that, using low drug doses, very high drug concentrations can be achieved in the cerebrospinal fluid (CSF) and relatively high concentrations in the leptomeninges but not in the brain tissue and the plasma. Therefore, this approach is not an effective treatment for bulky disease of brain tissue, and results in minimal systemic toxicity. In comparison with intralumbar administration, lower interpatient variability of CSF drug concentrations and improved clinical efficacy were observed. 'Concentration x time' schedules, i.e. frequent small drug doses over a short period, enable long-term CSF exposure to cytotoxic drug concentrations while avoiding excessively high and potentially neurotoxic drug concentrations. The technique of ventriculolumbar cerebrospinal perfusion delivers continuously high drug concentrations throughout the CSF for several hours, but its widespread use is limited by the technical complexities of this approach.In this article, the dosages, schedules and pharmacokinetic data of routinely used intraventricular agents in humans, e.g. methotrexate, cytarabine, glucocorticoids and thiotepa, are outlined in detail. In addition, pharmacokinetic data of investigational agents for intraventricular administration (diaziquone, DTC 101, mercaptopurine, mafosfamide, etoposide, topotecan, nimustine [ACNU] and bleomycin) are presented. Better understanding of the CSF pharmacology of these drugs is an essential prerequisite for safe, effective administration of these drugs. Investigational efforts are underway to verify the feasibility and efficacy of different dosages, schedules and combination therapies of these new intra-CSF agents. Current and future clinical research should also focus on methods allowing the delivery of tumoricidal drug concentrations for extended periods into the CSF and the brain tissue while minimising neurotoxicity and systemic toxicity (e.g. liposomal drug preparations, monoclonal antibodies, immunotoxins and gene therapy).     

Intrathecal methotrexate induces focal cognitive deficits and increases cerebrospinal fluid homocysteine

Although most children with acute lymphoblastic leukemia (ALL) can be cured, a significant subset of survivors manifests focal deficits in cognitive function, even when the treatment regimen does not include cranial radiation. Intrathecal administration of the folate antagonist methotrexate (MTX) is necessary to prevent leukemic relapse within the central nervous system, but is suspected to contribute to treatment-induced cognitive dysfunction. To better elucidate the underlying pathophysiology, we sought to establish a rodent model of the cognitive and neurotoxic effects resulting from direct administration of MTX into the cerebrospinal fluid (CSF). MTX or artificial CSF was injected via transcutaneous puncture at the level of the cisterna magna. Subsequent behavioral tests were designed to assess cognitive domains frequently impaired among children treated for ALL. MTX administration produced both recognition and spatial memory deficits, without altering general activity or motor coordination. In addition, MTX significantly reduced folate levels in both CSF and serum and increased CSF homocysteine. Thus, we have established an animal model that mimics the clinical effects of prophylactic intrathecal MTX on cognitive function. Using this model we can further study the pathophysiology of MTX-induced cognitive dysfunction and test protective interventions.     

Management of leptomeningeal malignancy

Leptomeningeal carcinomatosis is defined as malignant infiltration of the pia matter and arachnoid membrane. Leukaemias and lymphomas, lung, breast cancer and melanoma are the primary tumours commonly associated with leptomeningeal carcinomatosis. Diagnosis is based on compatible symptoms and signs, cytological evidence of malignancy in the cerebrospinal fluid, and neuroimaging studies. Treatment is largely palliative (median survival 2-4 months). Patients with lympomatous or leukaemic meningitis, chemosensitive tumours such as breast cancer, low tumour burden, minimal neurological deficits, good performance status and controllable systemic disease survive longer with occasional long-term responses. Available treatment options include focal radiation therapy to CNS sites of bulky, symptomatic or obstructive meningeal deposits, intrathecal cytotoxic therapy and systemic chemotherapy. No evidence of superiority of intrathecal treatment compared with best palliative care (including radiation therapy and systemic treatment) is available from clinical trials. Novel treatment approaches include intrathecal liposomal Ara-C, the development of new cytotoxic compounds, signal transduction inhibitors and monoclonal antibodies for intrathecal or systemic use. Until data from multi-centre randomised trials are available, rationalisation of therapy should be done by stratifying patients to prognostic groups. High-risk patients will only survive for a few weeks and are better managed with supportive measures, whereas low-risk patients justify vigorous cerebrospinal fluid-directed treatment combined with radiation therapy and systemic chemotherapy.     

Pharmacokinetics of nimustine, methotrexate, and cytosine arabinoside during cerebrospinal fluid perfusion chemotherapy in patients with disseminated brain tumors

Objective: This study was conducted to evaluate the pharmacokinetics of anticancer drugs in cerebrospinal fluid (CSF) perfusion chemotherapy. Methods: We administered CSF perfusion chemotherapy with nimustine (ACNU), methotrexate (MTX), and cytosine arabinoside (Ara-C) to three patients with disseminated malignant brain disease. The drugs were infused via Ommaya's reservoirs to the lateral ventricle and removed by drainage from the temporal lobe or lumbar spine. CSF and plasma concentrations of the anticancer drugs were determined by high-performance liquid chromatography and fluorescence polarization immunoassay. Results: The concentrations of anticancer drugs in the discharged CSF peaked about 40 min after the start of a 1-h CSF perfusion. After the perfusion, the drug level in CSF decreased exponentially in a monophasic manner. ACNU and Ara-C were not detectable in the discharged CSF in the temporal lobe at 6 h and 48 h after perfusion, respectively, but MTX was detectable at 48 h. The maximum concentration ratio of anticancer drugs and the duration of perfusion were inversely correlated. The plasma concentrations of anticancer drugs were much lower than those in CSF. The half-life of ACNU was very short (0.2–1.1 h), whereas the half-lives of MTX and Ara-C were relatively long (2.81–13.5 h and 1.84–6.25 h, respectively). The half-lives of the anticancer drugs in CSF tended to decrease with repeated CSF perfusion chemotherapy. Conclusion: Results suggest that CSF perfusion chemotherapy enables a high concentration of anticancer drug to be administered for dissemination in the spinal cord within a short period of time, with minimal adverse effects. Received: 17 September 1996 / Accepted in revised form: 21 April 1998     

Pharmacokinetics of cytosine arabinoside, methotrexate, nimustine and valproic acid in cerebrospinal fluid during cerebrospinal fluid perfusion chemotherapy

This report investigates the pharmacokinetics of cytosine arabinoside (Ara-C), methotrexate (MTX), nimustine (ACNU) and valproic acid (VPA) in cerebrospinal fluid (CSF) during CSF perfusion chemotherapy. A 28-year-old Japanese woman with disseminated glioblastoma was, on admission, on a stable oral regimen of prolonged-release VPA tablets (Depakene-R), 400 mg twice a day, for seizure control. Twelve courses of CSF perfusion chemotherapy with Ara-C, MTX, and ACNU were administered. Plasma samples and CSF samples via Ommaya reservoirs were obtained during the eleventh course of treatment. The Ara-C and ACNU concentrations were measured by HPLC. The MTX and VPA concentrations were measured by fluorescence polarization immunoassay. During CSF perfusion chemotherapy, the highest CSF concentrations of Ara-C, MTX, and ACNU were observed at the end of the perfusion and decreased in a monoexponential pattern. The half-lives of Ara-C, MTX, and ACNU were 2.65, 3.52, and 0.71 h, respectively. No anticancer drugs were detectable in plasma during CSF perfusion chemotherapy. Before CSF perfusion chemotherapy, the free VPA concentration in plasma was 14.4% of the total VPA concentration. The mean total and free VPA concentrations in plasma were 78.0+/-0.8 and 10.9-0.3 microg/ml, respectively. The free VPA concentrations in plasma and in CSF were of similar values. At the end of perfusion, the lowest free VPA concentration in CSF was 30.3% of that at the initiation of perfusion. The free VPA concentrations in CSF at 3, 7, 23, and 47 h after the end of perfusion were 79.8, 94.5, 100.9, and 100.9% respectively of that at the initiation of perfusion. During CSF perfusion chemotherapy, the ratio of free VPA concentrations to the total VPA in CSF was 86.3+/-6.9%. The VPA concentrations in CSF rapidly decreased during the CSF perfusion but recovered to pre-treatment levels within 7 h.     

Management of leptomeningeal malignancy

Leptomeningeal carcinomatosis is defined as malignant infiltration of the pia matter and arachnoid membrane. Leukaemias and lymphomas, lung, breast cancer and melanoma are the primary tumours commonly associated with leptomeningeal carcinomatosis. Diagnosis is based on compatible symptoms and signs, cytological evidence of malignancy in the cerebrospinal fluid, and neuroimaging studies. Treatment is largely palliative (median survival 2 – 4 months). Patients with lympomatous or leukaemic meningitis, chemosensitive tumours such as breast cancer, low tumour burden, minimal neurological deficits, good performance status and controllable systemic disease survive longer with occasional long-term responses. Available treatment options include focal radiation therapy to CNS sites of bulky, symptomatic or obstructive meningeal deposits, intrathecal cytotoxic therapy and systemic chemotherapy. No evidence of superiority of intrathecal treatment compared with best palliative care (including radiation therapy and systemic treatment) is available from clinical trials. Novel treatment approaches include intrathecal liposomal Ara-C, the development of new cytotoxic compounds, signal transduction inhibitors and monoclonal antibodies for intrathecal or systemic use. Until data from multi-centre randomised trials are available, rationalisation of therapy should be done by stratifying patients to prognostic groups. High-risk patients will only survive for a few weeks and are better managed with supportive measures, whereas low-risk patients justify vigorous cerebrospinal fluid-directed treatment combined with radiation therapy and systemic chemotherapy.     

Intrathecal topotecan in adult patients with neoplastic meningitis.

PURPOSE: The efficacy and safety of intrathecal topotecan were assessed in patients with neoplastic meningitis (NM) by retrospective chart review. SUMMARY: Fourteen patients (median age, 57 years) with NM were treated with the standard of care (i.e., regional or systemic chemotherapy or irradiation or both) plus intrathecal topotecan between January 2004 and September 2005. Three patients developed NM in the setting of systemic cancer; 11 patients had primary central nervous system (CNS) malignancies. All patients received 0.4 mg of topotecan intrathecally two times per week. The efficacy of intrathecal topotecan was assessed on the basis of the number of doses to cerebrospinal fluid (CSF) cytologic clearing--defined as the disappearance of malignant cells from a previously positive CSF cytology. Safety was evaluated by chart documentation of adverse events that might have been associated with topotecan given intrathecally. Of the 11 patients with primary CNS tumors, 6 patients achieved CSF clearing after the first dose of intrathecal topotecan, 2 patients after the second dose, and 1 patient after the fifth dose. For the 3 patients with secondary CSF tumors, 1 patient achieved CSF clearing after the third dose and 2 patients did not reach the primary endpoint. Overall, 6 of the 14 patients achieved CSF clearing after the first dose of intrathecal topotecan; in 10 of the 14 patients, CSF clearing of malignant cells was observed at some point during treatment. Toxicity was modest. The most common adverse effect reported was fatigue. CONCLUSION: Intrathecal topotecan appeared to be effective and safe in adult patients with NM.     

鞘内注射甲氨蝶呤和地塞米松治疗神经精神性狼疮的临床观察

目的探讨甲氨蝶呤和地塞米松鞘内注射治疗系统性红斑狼疮（SLE）中枢神经系统损害的效果。方法对18例鞘内注射的SLE中枢神经系统损害患者治疗前后的临床表现、脑脊液、头颅CT或磁共振成像（MRI）进行对比分析,并与27例未行鞘内注射者的情况进行对照。结果18例患者中1例死亡,其他患者病情均明显改善或完全缓解;脑脊液压力明显下降,蛋白水平降低,葡萄糖升高。结论甲氨蝶呤和地塞米松鞘内注射治疗SLE中枢神经系统损害有明显效果,能提高抢救成功率,副作用轻且少,值得临床推荐使用。     

Pharmacology of drugs formulated with DepoFoam: a sustained release drug delivery system for parenteral administration using multivesicular liposome technology

Lamellar liposome technology has been used for several decades to produce sustained-release drug formulations for parenteral administration. Multivesicular liposomes are structurally distinct from lamellar liposomes and consist of an aggregation of hundreds of water-filled polyhedral compartments separated by bi-layered lipid septa. The unique architecture of multivesicular liposomes allows encapsulating drug with greater efficiency, provides robust structural stability and ensures reliable, steady and prolonged drug release.The favourable characteristics of multivesicular liposomes have resulted in many drug formulations exploiting this technology, which is proprietary and referred to as DepoFoam. Currently, two formulations using multivesicular liposome technology are approved by the US FDA for clinical use, and many more formulations are at an experimental developmental stage. The first clinically available formulation contains the antineoplastic agent cytarabine (DepoCyt) for its intrathecal injection in the treatment of malignant lymphomatous meningitis. Intrathecal injection of DepoCyt reliably results in the sustained release of cytarabine and produces cytotoxic concentrations in cerebrospinal fluid (CSF) that are maintained for at least 2 weeks. Early efficacy data suggest that DepoCyt is fairly well tolerated, and its use allows reduced dosing frequency from twice a week to once every other week and may improve the outcome compared with frequent intrathecal injections of unencapsulated cytarabine. The second available formulation contains morphine (DepoDur) for its single epidural injection in the treatment of postoperative pain. While animal studies confirm that epidural injection of DepoDur results in the sustained release of morphine into CSF, the CSF pharmacokinetics have not been determined in humans. Clinical studies suggest that the use of DepoDur decreases the amount of systemically administered analgesics needed for adequate postoperative pain control. It may also provide superior pain control during the first 1-2 postoperative days compared with epidural administration of unencapsulated morphine or intravenous administration of an opioid. However, at this timepoint the overall clinical utility of DepoDur has yet to be defined and some safety concerns remain because of the unknown CSF pharmacokinetics of DepoDur in humans.The versatility of multivesicular liposome technology is reflected by the many agents including small inorganic and organic molecules and macromolecules including proteins that have successfully been encapsulated. Data concerning many experimental formulations containing antineoplastic, antibacterial and antiviral agents underscore the sustained, steady and reliable release of these compounds from multivesicular liposomes after injection by the intrathecal, subcutaneous, intramuscular, intraperitoneal and intraocular routes. Contingent on the specific formulation and manufacturing process, agents were released over a period of hours to weeks as reflected by a 2- to 400-fold increase in elimination half life. Published data further suggest that the encapsulation process preserves bioactivity of agents as delicate as proteins and supports the view that examined multivesicular liposomes were non-toxic at studied doses. The task ahead will be to examine whether the beneficial structural and pharmacokinetic properties of multivesicular liposome formulations will translate into improved clinical outcomes, either because of decreased drug toxicity or increased drug efficacy.     

Cerebrospinal fluid pharmacokinetics and toxicology of intraventricular and intrathecal arabinosyl-5-azacytosine (fazarabine,NSC 281272) in the nonhuman primate

Summary Arabinosyl-5-azacytosine (AAC), a new nucleoside antimetabolite, is broadly active in preclinical tumor screening evaluations. To assess the potential for intrathecal use of this drug, we studied the toxicity and pharmacokinetics of intrathecal and intraventricular administration in nonhuman primates.Four adult male rhesus monkeys were given single 10 mg intrathecal (n=1) or intraventricular (n=3) doses of AAC to determine its acute toxicity and pharmacokinetic parameters. An additional 3 animals were given four weekly 10 mg intrathecal doses to assess the systemic and neurologic toxicity associated with chronic administration.Disappearance from the cerebrospinal fluid (CSF) was biexponential, and CSF clearance was 0.2 ml/min, which exceeds the rate of CSF bulk flow by 5-fold. The peak CSF concentration and area under the concentrationx time curve achieved with the intraventricular administration of 10 mg were one hundred, and fifty fold greater, respectively, than those achieved after an intravenous dose of 200 mg/kg (1500–2400 mg) in prior experiments. No clinically evident neurotoxicity was observed in either the single or the weekly × 4 dose groups. A slight, transient CSF pleocytosis and increased CSF protein was observed. Systemic toxicity was limited to one animal in the weekly × 4 dose group who demonstrated a mild and transient decrease in his peripheral leukocyte count unassociated with a change in his hematocrit or platelet count.These studies in nonhuman primates demonstrate a clear pharmacokinetic advantage for intrathecal vs systemic administration of AAC. This is demonstrated by a 50-fold greater CSF drug exposure with an intrathecal or intraventricular dose 1/200th of that which can be given systemically. Intrathecal AAC was found to be safe on a weekly dosing schedule. On the basis of these results, human trials evaluating intrathecal AAC are planned.     

CNS prophylaxis using a triple intrathecal drug therapy without cranial irradiation in acute lymphoblastic leukaemia

After remission-induction chemotherapy in 31 patients with acute lymphoblastic leukaemia, patients immediately received CNS prophylaxis. Thirteen patients received triple intrathecal drug therapy, while 18 patients received intrathecal methotrexate and cranial irradiation; systematic chemotherapy was administered as well to both groups. Six patients developed CNS leukaemia during complete remission, 2 in the non-radiated patients and 4 in patients who had received cranial irradiation. Drug chemoprophylaxis may therefore substitute cranial radiotherapy when effective systemic regimens are used. Such CNS chemoprophylaxis will result in fewer, long-term CNS side-effects.     

Pharmacokinetic considerations in the treatment of CNS tumours

Despite aggressive therapy, the majority of primary and metastatic brain tumour patients have a poor prognosis with brief survival periods. This is because of the different pharmacokinetic parameters of systemically administered chemotherapeutic agents between the brain and the rest of the body. Specifically, before systemically administered drugs can distribute into the CNS, they must cross two membrane barriers, the blood-brain barrier (BBB) and blood-cerebrospinal fluid (CSF) barrier (BCB). To some extent, these structures function to exclude xenobiotics, such as anticancer drugs, from the brain. An understanding of these unique barriers is essential to predict when and how systemically administered drugs will be transported to the brain. Specifically, factors such as physiological variables (e.g. blood flow), physicochemical properties of the drug (e.g. molecular weight), as well as influx and efflux transporter expression at the BBB and BCB (e.g. adenosine triphosphate-binding cassette transporters) determine what compounds reach the CNS. A large body of preclinical and clinical research exists regarding brain penetration of anticancer agents. In most cases, a surrogate endpoint (i.e. CSF to plasma area under the concentration-time curve [AUC] ratio) is used to describe how effectively agents can be transported into the CNS. Some agents, such as the topoisomerase I inhibitor, topotecan, have high CSF to plasma AUC ratios, making them valid therapeutic options for primary and metastatic brain tumours. In contrast, other agents like the oral tyrosine kinase inhibitor, imatinib, have a low CSF to plasma AUC ratio. Knowledge of these data can have important clinical implications. For example, it is now known that chronic myelogenous leukaemia patients treated with imatinib might need additional CNS prophylaxis. Since most anticancer agents have limited brain penetration, new pharmacological approaches are needed to enhance delivery into the brain. BBB disruption, regional administration of chemotherapy and transporter modulation are all currently being evaluated in an effort to improve therapeutic outcomes. Additionally, since many chemotherapeutic agents are metabolised by the cytochrome P450 3A enzyme system, minimising drug interactions by avoiding concomitant drug therapies that are also metabolised through this system may potentially enhance outcomes. Specifically, the use of non-enzyme-inducing antiepileptic drugs and curtailing nonessential corticosteroid use may have an impact.     

Methotrexate concentration in cerebrospinal fluid of the space created by tumor removal

This paper investigates the post-surgical pharmacokinetics of methotrexate (MTX) in the plasma, the cerebrospinal fluids (CSF), and the spaces created by tumor removal (STR) in patients with glioblastoma, during hyperosmotic disruption of the blood brain barrier (HODBBB) and intra-arterial chemotherapy with MTX. Eight Japanese patients with glioblastoma, three with open STRs and five with closed STRs, received a total of thirteen courses of HODBBB and intra-arterial combination chemotherapy with MTX. The patients were initially administered mannitol, then the anticancer drugs were infused into the carotid artery. Samples of blood and CSF from the STRs were obtained. MTX concentrations were measured by fluorescence polarization immunoassay and the pharmacokinetic parameters of MTX in plasma and CSF were estimated. The plasma concentrations of MTX peaked at the end of drug infusion, and then decayed bi-exponentially during the remainder of the treatment period. The CSF concentration of MTX in the STR peaked 2 h after drug administration, then mono-exponentially decreased. The area under the concentration-time curve (AUC) for plasma and CSF MTX concentrations increased in parallel with the MTX dose. In patients with open STRs, the mean AUC of MTX in CSF was 4.44% of that found in plasma, while in patients with closed STRs, the mean was 61.2% of that found in plasma. In the latter group, the MTX administered using HODBBB and intra-arterial chemotherapy was maintained in the STRs for long periods.     

Muscle relaxant and neurotoxic activities of intrathecal baclofen in rats

Intrathecal baclofen therapy by the continuous intrathecal infusion of baclofen has been shown to be an effective treatment for spasticity in patients with spinal cord injury, cerebral palsy, traumatic brain injury, multiple sclerosis and other disorders. To demonstrate the efficacy and safety of intrathecal baclofen therapy, we investigated the muscle relaxant and neurotoxic activities of intrathecal baclofen in rats, compared with intravenous baclofen. Intrathecal and intravenous administration of baclofen dose-dependently inhibited the anemic decerebrate rigidity with ED₅₀ values of 0.31 μg/animal (=1.1–1.3 μg/kg) and 0.43 mg/kg, respectively. Intrathecal administration of baclofen induced no noticeable changes in a spontaneous electroencephalogram at 30 μg/animal. Intravenous administration of baclofen induced an abnormal electroencephalogram with flat waves in all the animals and the no-observed-effect level was estimated to be 5 mg/kg. In some animals, intravenous administration of baclofen induced sporadic spikes or sharp waves with background flat waves, indicating inhibitory and excitatory effects on the central nervous system. In conclusion, intrathecal administration of baclofen dose-dependently inhibited anemic decerebrate rigidity in rats and the effective dose was more than 300 times lower than that of intravenous baclofen. The safety margin of intrathecal baclofen was greater than that of intravenous baclofen (≥97 versus 12). These results suggest that intrathecal baclofen therapy is superior to systemic baclofen therapy in both efficacy and safety.     

Pharmacokinetics of methotrexate in the cerebrospinal fluid after intracerebroventricular administration in patients with meningeal carcinomatosis and altered cerebrospinal fluid flow dynamics

Pharmacokinetic parameters of the distribution and elimination of intracerebroventricularly administered methotrexate (MTX) were evaluated in three patients with meningeal carcinomatosis. Abnormal cerebrospinal fluid (CSF) flow dynamics, which were not otherwise clinically evident, were diagnosed by 111In-diethylenetriaminepentaacetate radionuclide imaging. Alterations in CSF flow resulted in large changes in MTX distribution. Reduced cortical convexity (type III), spinal subarachnoid (type II), or ventricular (type I) CSF flow resulted in a prolongation of the single-pass mean residence time of MTX in the peripheral compartment by as much as eightfold and a reduction in intercompartmental clearance by 94-99%. Leptomeningeal carcinomatosis can affect both CSF MTX distribution and elimination, each to a different extent, within the same patient. Total MTX clearance from the CSF was reduced by 79-93% in the patients studied. A two-compartment pharmacokinetic model, with elimination occurring from the peripheral compartment, gave values for the distribution rate constant from the central to the peripheral compartment (k12), which decreased with the extent of CSF flow abnormality. However, the elimination rate constant from the peripheral compartment (k20) was reduced to an extent apparently independent of CSF flow abnormality (percentage reduction in k12 and k20, respectively: type III, 18 and 66; type II, 67 and 86; type I, 78 and 48). Inadequate distribution and locally high concentrations of MTX within the CSF may contribute to therapeutic failure and neurotoxicity. Monitoring of MTX levels in the CSF may be deceiving when samples are drawn from the site of injection, since the distribution kinetics are altered by abnormal CSF flow dynamics.