Developmental pharmacokinetics and pharmacodynamics of nizatidine

OBJECTIVES: To characterize the impact of development on the pharmacokinetics and pharmacodynamics of nizatidine. METHODS: Children (age range, 5 days-18 years) and adults (age range, 18-50 years) were enrolled in four open-label trials. Nizatidine formulation and dose were determined by age: infants received 2 or 4 mg/kg i.v., children 2.5 or 5 mg/kg in one of three oral liquid formulations, and adolescents and adults received a fixed 150-mg capsule. Nizatidine and N-desmethylnizatidine concentrations were measured in serial post-dose plasma samples by a high-performance liquid chromatographic assay with mass spectrometric detection. Intragastric pH was recorded during a 24-hour post-dose interval. RESULTS: Data on 93 subjects were combined with previous values from 36 individuals to cover an age group not adequately captured and to control for formulation effects. Dose-normalized exposure estimates revealed no apparent age dependence; however, maximum plasma concentration (298.5 +/- 100.7 v 552.8 +/- 152.4 ng/mL per mg/kg dose) and AUC0-infinity (954.4 +/- 379.8 v 1,573.0 +/- 347.4 ng*hour/mL per mg/kg dose) were reduced in extemporaneous formulations in apple juice. The apparent modest age dependence observed for total body clearance (Cl/F) (r = 0.365) and Vss/F (r = 0.221) reflected a formulation-dependent decrease in bioavailability rather than a true age effect. The age-associated changes in lambda z observed for nizatidine and its metabolite were predictable and consistent with developmental acquisition of renal function. Mean and median pH, as well as fraction of time that the dosing interval remained above target pH values, were significantly greater with administration of the drug than without. CONCLUSIONS: The biodisposition of nizatidine in children and adults is similar; however, response after a comparable weight-based dose is equal and potentially greater in children.     

Paclitaxel-containing high-dose chemotherapy for relapsed or refractory testicular germ cell tumours

High-dose regimes containing etoposide, carboplatin and an oxazaphospharine can salvage 30-40% of patients with relapsed or refractory male germ cell tumours (GCTs). The additional benefit of paclitaxel in such high-dose therapy has not been tested. Between March 1995 and November 2002, 36 male GCT patients were treated with Carbop-EC-T (paclitaxel 75 mg x m(-2), etoposide 450 mg x m(-2), carboplatin AUC 10 on days -7, -5 and -3 and cyclophosphamide 60 mg x kg(-1) on days -5 and -3) followed by peripheral blood stem cell infusion (day 0). The 1-year overall survival rate for all patients is 67% (median follow-up 29 months). For the 24 patients with cisplatin-sensitive disease, the 1-year overall and event-free survivals are 88 and 64%, respectively. For those with cisplatin refractory or absolutely refractory disease, the 1-year overall survival is 25%. In all, 12 patients relapsed at a median duration of 5 months, 11 of whom have died. There were also six treatment-related deaths, five associated with pneumonitis. Pulmonary toxicity has been reported with paclitaxel in other high-dose regimes. Since altering our protocol so that paclitaxel is infused over 24 h with steroid prophylaxis, only one of 18 patients (13 testicular GCTs and five other tumour types) has had a treatment-related death. Our results suggest that Carbop-EC-T may enable a greater proportion of patients with relapsed and refractory GCTs to enter long-term remission.     

Reduced folate carrier and dihydrofolate reductase expression in acute lymphocytic leukemia may predict outcome: a Children's Cancer Group Study

PURPOSE: Methotrexate is a major component of current treatment regimens for children with acute lymphocytic leukemia (ALL). Potential mechanisms of methotrexate resistance include impaired drug uptake, decreased drug retention, and dihydrofolate reductase (DHFR) amplification. The purpose of this study was to assess whether reduced folate carrier (RFC) and DHFR expression in untreated leukemic blasts correlated with outcome. METHODS: Quantitative real-time RT-PCR was used to measure RFC and DHFR mRNA expression in leukemic blasts from 40 newly diagnosed patients with ALL obtained in a blinded fashion from Children's Cancer Group studies. RESULTS: Low RFC expression at diagnosis correlated significantly with an unfavorable event free survival. Surprisingly, low, not high, DHFR expression correlated significantly with an unfavorable event-free survival. Proliferative cell nuclear antigen (PCNA) expression demonstrated a weak inverse relationship between sample PCNA and DHFR or RFC expression, suggesting that DHFR and RFC expression may be markers for factors other than drug resistance. CONCLUSIONS: These results suggest that impaired transport may be an important mechanism of intrinsic methotrexate resistance in ALL, and DHFR expression also may be an important prognostic factor in ALL. Additional studies are necessary to clarify the mechanism for the correlation of low DHFR expression with poor outcome.     

Cisplatin neurotoxicity in the treatment of metastatic germ cell tumour: time course and prognosis

In order to ascertain the incidence and prognosis of cisplatin-induced neurotoxicity in testis cancer patients undergoing combination chemotherapy, 29 patients with metastatic disease were studied prospectively. Assessments included enquiry into neurological symptoms, measurement of sural nerve sensory action potential and conduction velocity, and vibration threshold in the left big toe. At the end of chemotherapy (3 to 4 cycles) only 3 out of 26 (11%) patients had paraesthesiae, but 3 months later the proportion rose to 65%. Resolution occurred in the majority over the ensuing 12 months so that only 17% had persistent symptoms. None of the 11 patients treated with 3 cycles of chemotherapy had persisting symptoms. Vibration thresholds showed a significant deterioration during chemotherapy (P = 0.032), further deterioration in the 3 months following chemotherapy (P = 0.009) and significant improvement between 3 and 12 months after chemotherapy (P = 0.038). Sural nerve sensory action potentials and conduction velocities were unhelpful.     

MRI diagnosis of intervertebral disk disease

Magnetic resonance imaging (MRI) is the leading diagnostic procedure for disk pathology and has overtaken other imaging modalities in frequency of use. However, one must be cautious not to overinterpret small abnormalities that are also frequent in asymptomatic subjects. There is conflicting evidence about the correlation of high-intensity zones with clinical symptoms. Bulging disks and protrusions are a common finding in asymptomatic individuals, whilst extrusions are almost always accompanied by back pain and sciatica. In patients with back pain or sciatica, MRI is indicated after failure of conservative management or neurological deterioration. Contrast-enhanced MRI is well suited to differentiate a recurrent disk extrusion from epidural fibrosis. In all cases suspicious of tumor or infection, MRI is indicated as a first-line investigation. The indications and pitfalls of the state of the art of MRI are delineated in this article.