Fluconazole penetration into cerebrospinal fluid: implications for treating fungal infections of the central nervous system.
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Animals↗
Biomedical subjects
D G Poplack
Publications and source records attributed to D G Poplack.
Bioavailability of oral trimetrexate in patients with acquired immunodeficiency syndrome.
The combination of the lipophilic antifolate trimetrexate and the rescue agent leucovorin has shown promise in the treatment of Pneumocystis carinii pneumonia in patients with acquired immunodeficiency syndrome. The pharmacokinetic behavior of trimetrexate administered either by intravenous bolus or orally was studied in six patients with acquired immunodeficiency syndrome with a reversed-phase high-pressure liquid chromatography assay. The mean clearance following bolus injection was 38 ml/min per m2, with a range of 15 to 55 ml/min per m2. The postdistributive half-life ranged from 6 to 16 h. With oral administration, the mean bioavailability was 44% (range, 19 to 67%). An oral dose of 60 mg/m2 (162 mumol/m2) resulted in concentrations in plasma that approximated those achieved with a 30-mg/m2 (81-mumol/m2) intravenous dose. The toxicity of this combination regimen was minimal. It appears that the oral route is a practical route of administration for trimetrexate in patients with acquired immunodeficiency syndrome requiring long-term outpatient treatment or prophylaxis for P. carinii pneumonia.
Acquired Immunodeficiency Syndrome↗
Pharmacokinetics of subcutaneous methotrexate.
The pharmacokinetics of subcutaneously administered methotrexate was studied as a parenteral alternative to oral administration. An initial feasibility study was performed in Rhesus monkeys comparing the subcutaneous route to intravenous (IV) injection and oral administration. The subcutaneous dose was completely absorbed and a sustained-release effect was observed when compared with the IV dose. No local or systemic toxicities resulted from subcutaneous methotrexate in the animals. Twelve children with acute lymphoblastic leukemia on maintenance therapy protocols prescribing either 7.5 mg/m2 biweekly or 40 mg/m2 weekly were also monitored after both a subcutaneous and an oral dose of methotrexate. Four children at the higher dosage level were also studied after an equal IV dose. The subcutaneous dose was again completely absorbed in these children at both dose levels, whereas the oral dose, which produced comparable plasma drug concentrations at the lower dosage level, resulted in a total drug exposure (area under the plasma concentration-time curve) that was one third that of the equal subcutaneous dose at the higher dosage level. No local or systemic toxicity was attributed to the subcutaneous methotrexate. Subcutaneous administration of methotrexate is well tolerated and well absorbed and appears to overcome the problems associated with oral administration, including variable absorption and saturation of the absorption mechanism with increasing doses.
Absorption↗
Late CNS sequelae in long term survivors of childhood leukemia.
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Adolescent↗
Pyrimidine dideoxyribonucleosides: selectivity of penetration into cerebrospinal fluid.
Cerebrospinal fluid (CSF)/plasma ratios of 1 to 30% were obtained in rhesus monkeys for the 3'-azido- and 2',3'-dideoxy-analogs of thymidine, deoxycytidine and deoxyuridine. Penetration of thymidine and deoxyuridine analogs was much greater than for deoxycytidine analogs. Octanol/buffer partition coefficients varied more than 30-fold, but did not correlate with CSF entry. Plasma protein binding was insignificant for all compounds. The presence or absence of the azido group at position 3' did not appear to influence the extent of CSF penetration. Although we do not fully understand the mechanistic basis for the penetration of these nucleosides into the CSF, it is apparent that the structural specificity is related more closely to the nucleobase than the sugar. Based upon elimination rates from the CSF after direct intrathecal injection, the differences in net penetration are determined by influx rather than efflux processes.
Animals↗
Intrathecal administration of 4-hydroperoxycyclophosphamide in rhesus monkeys.
The preactivated cyclophosphamide analogue, 4-HC, does not require activation by hepatic microsomal enzymes to express its cytotoxic activity and therefore, unlike cyclophosphamide, may be useful for the regional therapy of cancer. In the present study, the pharmacokinetics and toxicology of 4-HC were studied following intraventricular administration of 0.4 mg to rhesus monkeys with chronic indwelling Ommaya reservoirs. 4-HC was measured in cerebrospinal fluid (CSF) and plasma with a high-performance liquid chromatography assay utilizing a fluorometric detector following derivatization with m-aminophenol. The mean peak level of 4-HC in ventricular CSF was 100 microM 5 min after administration. The drug was cleared rapidly and the elimination was monoexponential with a mean half-life of 22 min. The mean clearance from CSF (0.33 ml/min) was 10-fold higher than CSF bulk flow. The drug was distributed throughout the subarachnoid space with lumbar levels approaching ventricular levels by 60 min. Neither acute nor chronic neurotoxicity or systemic toxicity was observed during the 6-wk observation period. Concentrations of 4-HC demonstrated to be cytocidal in vitro against human breast cancer, lymphoid leukemia, and rhabdomyosarcoma were readily achieved in CSF following intraventricular administration. This study demonstrates that intraventricular therapy with 4-HC is feasible and suggests that further study of this approach in the clinical setting should be considered.
Animals↗
The effect of methotrexate on the bioavailability of oral 6-mercaptopurine.
Fourteen children (aged 3 to 14 years) with average-risk acute lymphoblastic leukemia were studied after an oral dose of 6-mercaptopurine (6-MP) (75 mg/m2) administered alone and, on the next day, concurrently with oral methotrexate (20 mg/m2). When 6-MP was administered alone, both the peak plasma concentration (15 to 150 ng X ml-1) and the AUC (36 to 340 ng X ml-1 X hr) were highly variable. Concurrent methotrexate resulted in a 31% increase in the AUC (P less than 0.01) and a 26% increase in peak plasma levels (P less than 0.05) of 6-MP. The AUC of methotrexate correlated with the degree of increase in 6-MP plasma concentrations. These findings are consistent with previous in vitro studies demonstrating that methotrexate is an inhibitor of xanthine oxidase, the enzyme that catabolizes 6-MP to the inactive metabolite thiouric acid. Although the increases in 6-MP AUC and peak plasma concentrations resulting from concurrent methotrexate administration were statistically significant, this interaction is probably not clinically significant at standard low oral doses of methotrexate in light of the wide interpatient variability in these pharmacokinetic parameters of 6-MP.
Administration, Oral↗
Expression of a multidrug-resistance gene in human tumors and tissues.
The identification and cloning of a segment of a human multidrug resistance gene (mdr1) was reported recently. To examine the molecular basis of one type of multidrug resistance, we have prepared RNA from human tumors and normal tissues and measured their content of mdr1 RNA. We find that the mdr1 gene is expressed at a very high level in the adrenal gland; at a high level in the kidney; at intermediate levels in the lung, liver, lower jejunum, colon, and rectum; and at low levels in many other tissues. The mdr1 gene is also expressed in several human tumors, including many but not all tumors derived from the adrenal gland and the colon. In addition, increased expression was detected in a few tumors at the time of relapse following initial chemotherapy. Although controlled clinical studies will be required, our results suggest that measurement of mdr1 RNA may prove to be a valuable tool in the design of chemotherapy protocols.
Animals↗
Folate and methotrexate polyglutamate tissue levels in rhesus monkeys following chronic low-dose methotrexate.
Methotrexate (MTX), a mainstay in the treatment of acute lymphoblastic leukemia, is associated with both hepatic and neurologic toxicity. Like a folate, MTX is metabolized to polyglutamated derivatives (MTXGlun) with long intracellular half-lives. These metabolites may contribute to MTX toxicity through a direct effect on cellular metabolism or indirectly through a perturbation of folate homeostasis. To better define the effects of chronic MTX treatment, tissue levels of MTX, MTXGlun, and folate were measured in three monkeys treated with weekly intramuscular MTX for 1 year. Greater than 80% of the total tissue MTX found was in the form of polyglutamated derivatives. Most of these derivatives were MTXGlu3-5 but Glu6-7 were easily detectable. Total tissue folates were measured in liver, kidney, brain and testis with MTX treated animals having a 90% loss of total folate in brain tissue. This is of special interest since inborn errors of folate metabolism are often associated with severe neurologic abnormalities.
Animals↗
Infectious complications of intraventricular reservoirs in cancer patients.
Drug administration via an intraventricular reservoir is useful in the treatment of leukemic and carcinomatous meningitis that occurs in patients who have previously received lumbar intrathecal chemotherapy. The intraventricular route, however, is associated with a higher incidence of infectious complications compared with therapy given by the lumbar route. To characterize the infectious complications associated with such reservoirs, we reviewed the 10-year experience of the Pediatric Branch, National Cancer Institute, National Institutes of Health, and Children's Orthopedic Hospital, Seattle, WA, with 61 patients (49 with leukemia, 8 with lymphoma, 4 with solid tumors) who had intraventricular reservoirs placed for administration of chemotherapy. The reservoirs were in place for a median of 36 weeks and were punctured a median of 29.5 times, Infectious complications occurred in 14 of 61 patients (23%) and Propionibacterium acnes was the most common organism recovered from cultures. Twelve patients (19.7%) had 19 episodes of clinically suspected and microbiologically documented meningitis or of positive intraventricular reservoir cerebrospinal fluid cultures without symptoms which were treated successfully. Local cellulitis occurred at the site of intraventricular reservoir placement in 2 patients (3.3%) and removal of the intraventricular reservoir was necessary for successful management. Nine patients had their intraventricular reservoir removed (5 because of associated infection and 4 because of malfunction unassociated with infection).(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
T cell receptor alpha-, beta-, and gamma-genes in T cell and pre-B cell acute lymphoblastic leukemia.
We examined alpha-, beta-, and gamma-T cell receptor (TCR) gene activation within acute lymphoblastic leukemias (ALLs) that represent early stages of B and T cell development. We wished to determine if TCR rearrangement and expression was lineage restricted, showed any developmental hierarchy, or could identify new subsets of T cells. Rearrangement of gamma and beta TCR genes occurred early in development but in no set order, and most T-ALLs (22/26) were of sufficient maturity to have rearranged both genes. T-ALLs preferentially rearranged C gamma 2 versus the C gamma 1 complex; no preference within the beta locus was apparent. Once rearranged, the beta TCR continued to be expressed (11/13), whereas the gamma TCR was rarely expressed (3/14). The alpha TCR was expressed only in more mature T-ALLs (8/14) that usually displayed T3. The 3A-1 T cell associated antigen appeared earliest in development followed by T11 and T3. Within pre-B cell ALL a higher incidence of lineage spillover was noted for gamma TCR rearrangements (8/17) than for beta rearrangements (3/17). This also contrasts with the only occasional rearrangement of immunoglobulin (Ig) heavy chains (3/25) in T-ALL. However, in pre-B ALL the pattern of gamma TCR usage was distinct from that of T cells, with the C gamma 1 complex utilized more frequently. Almost all ALLs could be classified as pre-B or T cell in type by combining Ig and TCR genes with monoclonal antibodies recognizing surface antigens, although examples of lineage duality were noted. Unique subpopulations of cells were discovered including two genetically uncommitted ALLs that failed to rearrange either Ig or TCR loci. Moreover, two T lymphoblasts were identified that possessed the T3 molecule but failed to express alpha plus beta TCR genes. These T-ALLs may represent a fortuitous transformation of T cell subsets with alternative T3-Ti complexes.
B-Lymphocytes↗
Differences in cerebrospinal fluid penetration of corticosteroids: possible relationship to the prevention of meningeal leukemia.
The disposition of the synthetic corticosteroids, dexamethasone and prednisolone, in CSF was evaluated following bolus intravenous (IV) and intrathecal (IT) injection in a nonhuman primate model. Steroid concentration in plasma and CSF was measured with a radioimmunoassay following celite column chromatography. The CSF to plasma ratios of dexamethasone and prednisolone following IV bolus administration were 0.15 +/- 0.02 and 0.08 +/- 0.03, respectively. Although peak levels of the two steroids in the CSF reached equally potent levels when administered systemically in equipotent doses, the half-life of prednisolone in the CSF was shorter. In addition, there was a significant difference in the plasma protein binding of the two steroids, which may account for the differences in their CSF pharmacokinetics. Dexamethasone was 70% protein bound over a wide concentration range, while the protein binding of prednisolone was concentration dependent, ranging from 60% at 10 mumol/L to 95% at 0.5 mumol/L and below. After the initial distribution phase in plasma, CSF concentrations of dexamethasone and prednisolone approximated free plasma concentrations, indicating that penetration into the CSF was limited primarily by protein binding. At the plasma concentrations achieved following oral administration of standard doses of prednisone in children, the prednisolone (the active metabolite) is greater than 90% protein bound. The proportionally higher free plasma levels of dexamethasone result in greater penetration into the CSF. These findings may explain the lower rates of meningeal leukemia observed in children receiving dexamethasone instead of prednisone for the treatment of acute lymphoblastic leukemia (ALL).
Animals↗
Gene rearrangements as markers of clonal variation and minimal residual disease in acute lymphoblastic leukemia.
Immunoglobulin (Ig) heavy (H) and light (L) chain gene rearrangements were used as molecular markers of clonal evolution and minimal residual disease in B cell precursor acute lymphoblastic leukemia (ALL). All leukemic episodes within individual patients shared at least one identical Ig rearrangement and thus arose from a common clonal progenitor cell. Nine of 11 patients displayed completely identical patterns between leukemic episodes, while two of 11 patients demonstrated genetic progression between diagnosis and relapse as evidenced by additional rearrangements. These genetic changes marked the emergence of leukemic subclones. Ig gene rearrangements were also used as sensitive markers to identify clonal cell populations in ALL patients following induction or reinduction therapy and to search for residual bone marrow disease in patients in clinical remission or with isolated extramedullary relapse. DNA rearrangements provide tumor-specific markers to follow the genetic variation of ALL and may facilitate the early detection of recurrent disease.
B-Lymphocytes↗
Transient acute hepatotoxicity of high-dose methotrexate therapy during childhood.
Serial liver-enzyme determinations were performed on 36 children with acute lymphoblastic leukemia who were randomized to receive either conventional intrathecal methotrexate (MTX) therapy with cranial irradiation, or an investigational high-dose MTX regimen consisting of 10 courses of 33,600 mg/m2 over 24 hours, with high-dose leucovorin rescue. Both groups of patients received intermittent low-dose oral MTX during maintenance therapy. Serum transaminase elevations in the group of conventionally treated patients were infrequent and moderate in severity (less than 300 IU/liter). In the investigational group, however, the majority of patients had severe, acute increases in SGPT (greater than 300 IU/liter), with peaks up to 1000 to 2000 IU/liter. The incidence and severity of acute transaminasemia were directly proportional to the number of high-dose MTX courses received: courses 1, 2, 3, 4, 5, and 6 caused transaminase elevations in 31%, 50%, 50%, 73%, 100%, and 100% of courses, respectively, and 0%, 14%, 20%, 44%, 55%, and 92%, respectively, were over 300 IU/liter. Patients in both treatment groups developed a pattern of increasing serum alkaline phosphatase concentrations after initiation of low-dose oral MTX therapy; isoenzyme analysis indicated that this effect was osseous rather than hepatic. Serum bilirubin was rarely elevated. Transaminases returned to normal within 1 to 2 weeks after each high-dose MTX treatment, and with follow-up for as long as 7 years, no patient has developed clinical evidence of residual liver disease, after 3 years of high-dose MTX therapy and multiple other antileukemia drugs. The acute hypertransaminasemia frequently observed after high-dose MTX therapy is transient and reversible, and, in children, does not appear to result in chronic liver disease.
Adolescent↗
Stability of 5-fluorouracil in whole blood and plasma.
We studied the stability of 5-fluorouracil (5-FU) in plasma and whole blood kept at room temperature and on ice for 1 to 24 h. At room temperature, there was a steady loss of 94% of the parent drug over 24 h in whole blood and 52% in plasma. In the presence of an excess of uracil, 5-FU was stable for 24 h, suggesting that the loss of 5-FU is the result of enzymatic degradation. 5-FU is more stable in whole blood and plasma when samples are kept cold. For blood and plasma samples maintained on ice, the loss was only 30% and 10% of the parent drug in the respective samples over 24 h. Frozen plasma samples (-20 degrees C) were stable for five weeks. Blood specimens collected for quantifying 5-FU should be immediately placed on ice, and the plasma should be separated and frozen as promptly as possible.
Drug Stability↗
Adverse prognostic influence of hepatitis B virus infection in acute lymphoblastic leukemia.
Liver function test abnormalities were examined in a retrospective survey in a population of 90 children with acute lymphoblastic leukemia (ALL) treated in a similar fashion with therapy, using primarily methotrexate, mercaptopurine, vincristine, and prednisone. A twofold or greater elevation of serum glutamyl pyruvic transaminase (SGPT) was found in 80% of the patients during induction therapy, in 63% of the patients during maintenance therapy, and 31% of the patients who completed therapy. Circulating hepatitis B virus surface antigen (HBsAg) was noted in 26% of patients with liver function test abnormalities during maintenance therapy, and 45% of patients with liver function test abnormalities after the completion of therapy. Hepatitis B virus infection was therefore, the most important single cause of abnormal liver function during remission in our patient population. Though others have asserted that hepatitis B virus infection is relatively benign in immunosuppressed individuals, in our population, this agent often caused severe pathological and clinical sequelae. This may be related to the high frequency (50%) of co-infection with the delta agent in our HBsAg-positive patients. Furthermore, hepatitis B virus surface antigenemia conferred an adverse prognostic influence for these children in terms of their leukemia-free survival.
Acute Disease↗
The pharmacology of orally administered chemotherapy. A reappraisal.
Rational treatment of pediatric malignancies requires a detailed knowledge of the clinical pharmacology of those antineoplastic agents used therapeutically. A number of different agents are administered by the oral route. Recently, the clinical pharmacology of 6-mercaptopurine (6-MP) and methotrexate (MTX), the two agents that are the mainstay of maintenance chemotherapy in acute lymphoblastic leukemia (ALL), were investigated. Studies of oral 6-MP indicate that, contrary to previous information, the bioavailability of this drug is relatively poor after oral administration, and that plasma 6-MP concentrations achieved after uniform oral dosing are highly variable. Similarly, study of the pharmacology of orally administered MTX indicates that there is little correlation between MTX dose and the peak serum level achieved. These findings suggest that some patients may not be exposed to adequate systemic concentrations of 6-MP and/or MTX after oral administration, and raise the possibility that the development of relapse in some patients with ALL may be the result of a pharmacologic failure of oral maintenance therapy. A comprehensive prospective study of the clinical pharmacology of MTX and 6-MP in patients with ALL undergoing maintenance chemotherapy is currently in progress.
Administration, Oral↗
The effect of amitriptyline on the central nervous system penetration of methotrexate.
The reported ability of amitriptyline to enhance the penetration of diffusion limited substances across the blood brain barrier was investigated. The CSF:plasma ratio of methotrexate in primates was not significantly altered by amitriptyline pretreatment. Nor was methotrexate plasma clearance altered.
Amitriptyline↗