Bilateral Internuclear Ophthalmoplegia as a Presenting Manifestation of Primary Sjögren's Syndrome.

Bilateral internuclear ophthalmoplegia has been linked with various pathological conditions of the central nervous system (CNS), such as multiple sclerosis, stroke, tumours, and brainstem inflammatory processes. Herein the authors report a case of a 45-year-old female patient who presented with diplopia due to bilateral internuclear ophthalmoplegia, with no evidence of brainstem lesion in brain magnetic resonance imaging (MRI) and was diagnosed with primary Sjögren's syndrome.

Pheochromocytoma crisis presenting with cardiogenic shock.

Pheochromocytoma is a catecholamine-secreting tumor of the adrenal glands whose typical presentation includes the triad of headache, palpitations, and diaphoresis. Pheochromocytoma crisis is an urgent medical condition whose diagnosis and management constitute a challenge for physicians. We present the case of a 55-year-old man who developed cardiogenic shock in the setting of a pheochromocytoma crisis. After stabilizing blood pressure with combined administration of α- and ß-blockers, the tumor was surgically removed. Our diagnostic and therapeutic challenges are discussed.

A new model for determining the MTD during phase-I trials in pediatric oncology.

The primary goal of phase I studies in oncology is to determine the MTD (Maximum Tolerated Dose) for a drug. This MTD is determined with respect to an accepted risk (usually 33%) to see a limiting toxity for patients. In this paper we propose a new mathematical model to determine the MTD. An important feature of this model is that the limiting toxicity can be formulated as a combination of several basic graded toxicities such as hematologic or neurological. Another feature is the possibility to take into account several patient covariates to individualize the determination of the MTD. The model is a bayesian model where some prior information has been considered. The model is expected to work better than traditional empirical schemes for determining the MTD because it uses at every step all the available information on patients, and adds some major improvements as compared with existing CRM strategies because it uses whole data made available, including low-grades toxicities. Finally the model has been validated with a retrospective data set on 17 patients from a phase I study on paclitaxel in pediatric oncology. Calculated MTDs for each patient were found to be markedly different than the doses actually given following a traditional dose-escalation methodology. Results suggest that our new model provides a better and safer way to drive dose-escalation in phase-I trials as compared with traditional schemes.

Tumor growth modeling from clinical trials reveals synergistic anticancer effect of the capecitabine and docetaxel combination in metastatic breast cancer.

PURPOSE: Most of the cancer chemotherapy treatments employ drugs in combination. For combination treatments, it is relevant to assess interaction between two or more anticancer agents used in clinics. Based on clinical data and using modeling techniques, the work analyzes the pharmacodynamic interaction between capecitabine and docetaxel used in combination in metastatic breast cancer. METHODS: We developed mathematical models to describe tumor growth inhibition profile under treatment based on Phase II and Phase III clinical data of capecitabine and docetaxel in metastatic breast cancer. Model parameters were estimated by population approach with NONMEM(®) on single-agent and combination data. Simulations were performed using MATLAB. RESULTS: Capecitabine and docetaxel combination in metastatic breast cancer results in a synergistic effect as compared with the simple additive effects of single-agent treatments. Docetaxel is more efficient than capecitabine at the start of treatment but develops resistance faster. Modeling revealed no resistance of capecitabine for the combination data. CONCLUSIONS: Modeling could be a powerful tool to design the most advantageous combination regimen for capecitabine and docetaxel in metastatic breast cancer in order to increase the time before regrowth and decrease the tumor size at regrowth.

An interface model for dosage adjustment connects hematotoxicity to pharmacokinetics.

When modeling is required to describe pharmacokinetics and pharmacodynamics simultaneously, it is difficult to link time-concentration profiles and drug effects. When patients are under chemotherapy, despite the huge amount of blood monitoring numerations, there is a lack of exposure variables to describe hematotoxicity linked with the circulating drug blood levels. We developed an interface model that transforms circulating pharmacokinetic concentrations to adequate exposures, destined to be inputs of the pharmacodynamic process. The model is materialized by a nonlinear differential equation involving three parameters. The relevance of the interface model for dosage adjustment is illustrated by numerous simulations. In particular, the interface model is incorporated into a complex system including pharmacokinetics and neutropenia induced by docetaxel and by cisplatin. Emphasis is placed on the sensitivity of neutropenia with respect to the variations of the drug amount. This complex system including pharmacokinetic, interface, and pharmacodynamic hematotoxicity models is an interesting tool for analysis of hematotoxicity induced by anticancer agents. The model could be a new basis for further improvements aimed at incorporating new experimental features.

New adaptive method for phase I trials in oncology.

Assessment of the maximum tolerated dose for a small sample of patients is the objective of phase I trials in oncology. We propose a new adaptive approach performing differentiation of each type of toxicity and their grades, definition of the dose-limiting toxicity as a logical combination of toxicity events, modeling of the risk of toxic events as a function of the drug dose, and integration of individual covariates. An application study with retrospective data from a phase I Taxol pediatric trial revealed age as an influential covariate, allowing individualization of a patient's maximum tolerated dose. A simulation study illustrates the practice of sequential inclusion of patients, of constraints in the dose-finding process and of trial stopping rules. The approach presented here allows quick maximum tolerated dose assessment with a small sample of patients and assists the design of phase I trials in oncology.

Percutaneous closure of patent foramen ovale: success and outcomes of a low-volume procedure at a rural medical center.

BACKGROUND: Percutaneous patent foramen ovale (PFO) closure is indicated for recurrent cryptogenic stroke occurring on anticoagulant therapy. Few patients meet this criterion, and the safety of this procedure when performed infrequently is unclear. METHODS: Fifty-two patients with cryptogenic stroke (66%) or transient ischemic attack (34%) undergoing PFO closure from June 2001 to December 2004 were analyzed. CardioSEAL, Amplatzer or Cardia Star devices were used. Patients were discharged on aspirin, clopidogrel or (at the discretion of the neurologist) coumadin for 6 months. RESULTS: The study population was young (mean age 51 years) and included 25 males (48%). Seventeen patients (34%) had atrial septal aneurysms. Balloon-stretched PFO size ranged from 6 to 25 mm. Deployment success was 100%; mild residual shunting persisted in 10 patients (19%) at hospital discharge. Mean length of stay was 1 day. Predischarge complications included bleeding in 4 patients and arrhythmia in 3 patients. At 28-month follow up, 4 patients reported spells of uncertain etiology and 1 had paroxysmal atrial fibrillation. There were no transient ischemic attacks or strokes. One patient died of renal failure and sepsis unrelated to PFO closure. CONCLUSION: Low-volume PFO closure (15 per year) can be performed safely and effectively in a moderate-volume interventional laboratory with good short-term clinical results.

Endoscopic snare resection of an intrapapillary pedunculated villous adenoma presenting as acute recurrent pancreatitis.

Tumors of the papillary region are an unusual and heterogeneous group of neoplasms that arise from the major papilla, the ampulla of Vater, and the peripapillary duodenum. Benign adenomas of the papilla of Vater are an increasingly recognized condition in those with familial adenomatous polyposis syndromes as well as sporadic cases. Papillary adenoma is a recognized but rare cause of acute pancreatitis. We describe a patient who presented with acute recurrent pancreatitis that was attributed to an intrapapillary pedunculated villous adenoma. Following diagnosis by endoscopic needle knife sphincterotomy and endoscopic retrograde cholangiopancreatography, endoscopic snare resection of the adenoma resulted in symptomatic improvement.

Endobiliary endoprosthesis without sphincterotomy for the treatment of biliary leakage.

Endoscopic retrograde cholangiopancreatography with biliary drainage is an effective therapeutic tool in the management of bile duct injuries associated with laparoscopic cholecystectomy. Placement of a stent or a nasobiliary drain in the common bile duct, or biliary sphincterotomy, is an effective treatment for bile leaks and obviates the need for otherwise complex biliary tract surgery. Although there are no controlled comparative trials, placement of a 7-, 8.5-, or 10-Fr biliary stent without sphincterotomy may cause the least morbidity and be the most comfortable nonoperative management option. We report a child who presented with a bile leak that occurred after laparoscopic cholecystectomy and was successfully treated with the placement of a biliary stent without sphincterotomy. To our knowledge, this is the second pediatric case of a bile leak successfully treated by endoprosthesis placement without sphincterotomy.

Double Dieulafoy-like lesion in the stomach.

Dieulafoy's lesion is an uncommon cause of major gastrointestinal bleeding and may be difficult to recognize. It consists of an arteriole that protrudes through a tiny mucosal defect usually within 6 cm of the gastroesophageal junction on the lesser curve of the stomach. Despite widespread awareness of this entity, it remains a diagnostic challenge for gastroenterologists because of its small size and hidden location. Emergency endoscopy is the most effective method of diagnosing the disease. We report a patient, with double Dieulafoy-like lesion, who was successfully treated endoscopically using hemostatic clip application. The characteristics of the Dieulafoy's lesion, its current diagnosis, and its treatment are discussed.

Hemolysis caused by G-6PD deficiency after a difficult and prolonged therapeutic endoscopic retrograde cholangiopancreatography.

Endoscopic retrograde cholangiopancreatography (ERCP), together with its substantial therapeutic capabilities, carries a higher potential for complications than other endoscopic procedures. Common major complications specific to pancreaticobiliary instrumentation include pancreatitis, post-sphincterotomy hemorrhage, perforation, and cholangitis with or without systemic sepsis. Two patients underwent therapeutic ERCP for recurrent episodes of abdominal pain and elevation of hepatobiliary enzymes. Endoscopic sphincterotomy was difficult and prolonged. The calculi were successfully extracted by sweeping the choledochus with a balloon-tipped catheter or basket in both cases. The patients experienced postprocedure diffuse abdominal pain unassociated with nausea or vomiting. Laboratory data showed normal serum amylase and lipase 2, 6, and 18 h after the end of procedure, a fall in hematocrit level, and an increase of indirect bilirubin and lactic dehydrogenase. The abdominal pain subsided in 4 to 6 h. The hematocrit level remained stable during the next 3 days, and the patients were very well when discharged. Examination of glucose-6-phosphate dehydrogenase (G-6PD) enzyme levels in red cells 20 days later showed complete enzyme deficiency. This report highlights the importance of examining G-6PD deficiency in patients with post-ERCP abdominal pain, normal serum amylase and lipase, and laboratory findings of hemolysis.

Fractal volume of drug distribution: it scales proportionally to body mass.

PURPOSE: To develop the physiologically sound concept of fractal volume of drug distribution, vf, and evaluate its utility and applicability in interspecies pharmacokinetic scaling. METHODS: Estimates for vf of various drugs in different species were obtained from the relationship: vf = (v - Vpl)(Vap - Vpl)/V + Vpl where v is the total volume of the species (equivalent to its total mass assuming a uniform density Ig/mL), Vpl is the plasma volume of the species and Vap is the conventional volume of drug distribution. This equation was also used to calculate the fractal analogs of various volume terms of drug distribution (the volume of central compartment, Vc, the steady state volume of distribution, Vss, and the volume of distribution following pseudodistribution equilibrium, Vz). The calculated fractal volumes of drug distribution were correlated with body mass of different mammalian species and allometric exponents and coefficients were determined. RESULTS: The calculated values of vf for selected drugs in humans provided meaningful and physiologically sound estimates for the distribution of drugs in the human body. For all fractal volume terms utilized, the allometric exponents were found to be either one or close to unity. The estimates of the allometric coefficients were found to be in the interval (0,1). These decimal values correspond to a fixed fraction of the fractal volume term relative to body mass in each one of the species. CONCLUSIONS: Fractal volumes of drug distribution scale proportionally to mass. This confirms the theoretically expected relationship between volume and mass in mammalian species.

Nonlinear dynamics and chaos theory: concepts and applications relevant to pharmacodynamics.

The theory of nonlinear dynamical systems (chaos theory), which deals with deterministic systems that exhibit a complicated, apparently random-looking behavior, has formed an interdisciplinary area of research and has affected almost every field of science in the last 20 years. Life sciences are one of the most applicable areas for the ideas of chaos because of the complexity of biological systems. It is widely appreciated that chaotic behavior dominates physiological systems. This is suggested by experimental studies and has also been encouraged by very successful modeling. Pharmacodynamics are very tightly associated with complex physiological processes, and the implications of this relation demand that the new approach of nonlinear dynamics should be adopted in greater extent in pharmacodynamic studies. This is necessary not only for the sake of more detailed study, but mainly because nonlinear dynamics suggest a whole new rationale, fundamentally different from the classic approach. In this work the basic principles of dynamical systems are presented and applications of nonlinear dynamics in topics relevant to drug research and especially to pharmacodynamics are reviewed. Special attention is focused on three major fields of physiological systems with great importance in pharmacotherapy, namely cardiovascular, central nervous, and endocrine systems, where tools and concepts from nonlinear dynamics have been applied.

Diazepam poisoning with one-month monitoring of diazepam and nordiazepam blood levels.

A 54-y-old man ingested 2 g of bulk laboratory diazepam and was treated with activated charcoal, enhanced diuresis and flumazenil infusion. The treatment resulted in awakening, but the patient had drowsiness, dysarthria, diplopia, and dizziness for 9 d. Blood levels of diazepam and its main metabolite, nordiazepam, were obtained for 1 mo. The half-lives in this benzodiazepine overdose were longer than those seen with therapeutic doses. Benzodiazepines should not be readministrated when patients awake after suicide attempts.

Phase I trial and pharmacological study of a 3-hour paclitaxel infusion in children with refractory solid tumours: a SFOP study.

The maximum tolerated dose of paclitaxel administered by 24-hour continuous infusion in children is known. Short infusion might offer equivalent antitumour efficacy and reduced haematological toxicity, without increasing the allergic risk. Our aims were to determine the maximum tolerated dose and the pharmacokinetics of paclitaxel in children when administered in 3-h infusion every 3 weeks. Patients older than 6 months, younger than 20 years with refractory malignant solid tumours were eligible when they satisfied standard haematological, renal, hepatic and cardiologic inclusion criteria with life expectancy exceeding 8 weeks. Paclitaxel was administered as a 3-hour infusion after premedication (dexamethasone, dexchlorpheniramine). Pharmacokinetic analysis and solvent assays (ethanol, cremophor) were performed during the first course. 20 courses were studied in 17 patients; 4 dosage levels were investigated (240 to 420 mg/m(2)). No dose-limiting haematological toxicity was observed. Severe acute neurological and allergic toxicity was encountered. One treatment-related death occurred just after the infusion at the highest dosage. Delayed peripheral neurotoxicity and moderate allergic reactions were also encountered. Pharmacokinetic analysis showed dose-dependent clearance of paclitaxel and elevated blood ethanol and Cremophor EL levels. Although no limiting haematological toxicity was reached, we do not recommend this paclitaxel schedule in children because of its acute neurological toxicity.

New approach for accurate simulation of human pharmacokinetics in an in vitro pharmacodynamic model: application to ciprofloxacin.

An in vitro pharmacodynamic model using a disposable dialyser unit and computer-controlled devices was developed. Feedback control of peristaltic pump flow rates is used to maintain constant flow rates, thus avoiding the problem of the modification of the physical properties of the tubing that generally occurs. Fast equilibrium is obtained with capillaries, which allows simulation of the same kinetic profile in the central and the peripheral compartments. Thus, more accurate simulation of plasma, extracapillary fluid or whole tissue kinetics can be performed. Our model was validated by simulation of a 30 min infusion of a 200 mg dose, and of an oral administration of a 500 mg dose of ciprofloxacin.

Optimizing drug regimens in cancer chemotherapy: a simulation study using a PK-PD model.

In cancer chemotherapy, it is important to design treatment strategies for drug protocols that ensure a desired rate of tumor cell kill without overdosing the host. Mathematical modeling was used for optimization in which we minimize the end value of the tumor cells while limiting toxicity by always maintaining the white blood cell count beyond a limit. The optimal solution for this is a mixture of an initial bolus application of drug followed by no drug and then continuous infusion that keeps the normal cell population at its lower limit while decreasing the tumor cell population.

Combination of thymidine phosphorylase gene transfer and deoxyinosine treatment greatly enhances 5-fluorouracil antitumor activity in vitro and in vivo.

We reported previously that 5-fluorouracil (FUra) efficacy could be enhanced by increasing tumoral thymidine phosphorylase (TP) activity. Potentiated TP yield was achieved by either transfecting cells with human TP gene (A. Evrard et al., Br. J. Cancer, 80: 1726-1733, 1999) or associating FUra with 2'-deoxyinosine (d-Ino), a modulator providing the tumors with TP cofactor deoxyribose 1-phosphate (J. Ciccolini et al., Clin. Cancer Res., 6: 1529-1535, 2000). The purpose of the present work was to study the effects of a combined modulation (TP gene transfer + use of d-Ino) on the sensitivity to FUra of the LS174T human colorectal cell line. Results showed a near 4000 times increase of cell sensitivity in vitro after double (genetic + biochemical) modulation. This potentiation of tumor response was accompanied by a total change in the FUra anabolic pathway with a 5000% increase of cytosolic fluorodeoxyuridine monophosphate, a stronger and longer inhibition of thymidylate synthase, and 300% augmentation of DNA damage. Besides, whereas thymidine failed to inhibit FUra cytotoxicity in LS174T wild-type cells, the potentiation of the antitumor activity observed in the modulating regimen was partly reversed by thymidine, indicative of thymidylate synthase as the main drug target. The impact of this double modulation was next investigated in xenograft-bearing nude mice. Results showed that whereas FUra alone was completely ineffective on wild-type tumor growth, the size of TP-transfected tumors in animals treated with the FUra/d-Ino combination was reduced by 80% (P < 0.05). Our results suggest that FUra exhibits stronger antiproliferative activity when activated via TP through the DNA pathway and that high tumoral TP activity therefore leads to enhanced sensitivity to fluoropyrimidines.

Information tools for exploratory data analysis in population pharmacokinetics.

For a group of individuals, population pharmacokinetic studies describe the interindividual variability through a statistical distribution. These studies conducted during the drug development serve as a useful marker of the safety of the drug, provide information that might be decisive for future experiments and, in a clinical context, help establish guidelines for optimal use in each patient. As complementary tools to the existing statistical and graphical techniques for population pharmacokinetic data analysis, indexes derived from information theory were used to select the most appropriate modelfor the statistical distribution, to detect atypical individuals, and to screen influential covariates. The rationale for using these indexes is shown using simulated and real data.