Unexplained spikes in lamotrigine serum concentration: nonlinear elimination?

OBJECTIVES: The objective of this study was to evaluate possible nonlinear lamotrigine (LTG) pharmacokinetics at elevated concentration. LTG is reported to have linear kinetics, so that elimination rate is linearly proportional to blood concentration and a change in dose is accompanied by a proportionate change in serum concentration. We encountered patients in whom LTG serum concentration increased dramatically in response to minor or no change in LTG dose. We studied this phenomenon in patients with LTG toxicity in one clinic. MATERIALS AND METHODS: Using electronic medical records from 1997 to 2014, we identified patients who developed clinical LTG toxicity with LTG serum concentrations >20 mg/l, after tolerating lamotrigine at lower serum concentrations. We reviewed LTG dose change and other changes that preceded the episode of toxicity. RESULTS: Twenty-two patients had at least one episode of LTG toxicity with levels higher than 20 mg/l (of 922 patients with available levels). The peak serum concentration varied from 21.1 to 40.3 mg/l (mean 28.7). The increase in level was explained in three patients (post-delivery in one, addition of valproate in two). In the 18 others, the increase was not explained or it was disproportionate to an increase in LTG dose. CONCLUSIONS: Spikes in LTG levels and associated clinical toxicity may occur unexpectedly, suggesting that elimination kinetics may be nonlinear in some individuals at serum concentrations in the upper range. Measurement and close monitoring of LTG levels is warranted for new symptoms that could be consistent with lamotrigine toxicity, particularly when the baseline serum concentration has been >10 mg/l.

What do the suffixes--XR, ER, Chrono, Chronosphere--really mean as it pertains to modified-release antiepileptic drugs?

BACKGROUND: Epilepsy is a disease requiring chronic therapy with antiepileptic drugs (AEDs). Many conventional AEDs currently available have either too rapid an absorption or elimination, requiring the patient to take multiple doses per day, which may adversely impact adherence or cause peak-related side-effects. Consequently, some AEDs with immediate-release characteristics have been modified to prolong absorption and/or reduce peak serum concentration, enabling dosage regimen simplification. Modified-release (MR) AED formulations have been labelled with various suffixes or names ('XR, ER, -Chrono, -Chronosphere'), but such labelling may not adequately distinguish those MR AEDs with the most prolonged absorption or unique formulation characteristics. Such suffixes lack precise definition. OBJECTIVE: We identified the formulation characteristics of currently available MR AEDs, attempting to distinguish them by suffix designation. DESIGN/METHODS: Nine MR AED formulations, representing six different AEDs, were characterized, utilizing information from FDA-approved inserts (2001 +) and published literature. RESULTS: The formulation characteristics of commercially available MR AEDs are quite variable and do not appear to correlate with their brand name suffix. CONCLUSIONS: When all MR AEDs are compared, suffix designations do not provide distinguishable information about formulation characteristics. Clarification of MR AED suffix terminology may be warranted.

Synthetic bone: Design by additive manufacturing.

A broad range of synthetic trabecular-like metallic lattices are 3D printed, to study the extra design freedom conferred by this new manufacturing process. The aim is to propose new conceptual types of implant structures for superior bio-mechanical matching and osseo-integration: synthetic bone. The target designs are 3D printed in Ti-6Al-4V alloy using a laser-bed process. Systematic evaluation is then carried out: (i) their accuracy is characterised at high spatial resolution using computed X-ray tomography, to assess manufacturing robustness with respect to the original geometrical design intent and (ii) the mechanical properties - stiffness and strength - are experimentally measured, evaluated, and compared. Finally, this new knowledge is synthesised in a conceptual framework to allow the construction of so-called implant design maps, to define the processing conditions of bone tailored substitutes, with focus on spine fusion devices. The design criteria emphasise the bone stiffness-matching, preferred range of pore structure for bone in-growth, manufacturability of the device and choice of inherent materials properties which are needed for durable implants. Examples of the use of such maps are given with focus on spine fusion devices, emphasising the stiffness-matching, osseo-integration properties and choice of inherent materials properties which are needed for durable implants. STATEMENT OF SIGNIFICANCE: We present a conceptual bio-engineering design methodology for new biomedical lattices produced by additive manufacturing, which addresses some of the critical points in currently existing porous implant materials. Amongst others: (i) feasibility and accuracy of manufacturing, (ii) design to the elastic properties of bone, and (iii) sensible pores sizes for osseointegration. This has inspired new and novel geometrical latticed designs which aim at improving the properties of intervertebral fusion devices. In their fundamental form, these structures are here fabricated and tested. When integrated into medical devices, these concepts could offer superior medical outcomes.

Complications of percutaneous thoracostomy in neonates and infants.

OBJECTIVE: Percutaneous thoracostomy tubes are widely used in neonates, infants and children. The technique has a low complication rate. Lung perforation by a pigtail catheter is described in a single case report. STUDY DESIGN: This is a multi-center case series of neonates and infants who experienced thoracic organ injury following percutaneous chest tube placement between 2006 and 2015. RESULT: Eleven patients had chest tube-related thoracic organ injury. In six, tubes were placed during resuscitation. Gestational ages ranged from 24+6 weeks to term. Most of the chest tubes were pigtail catheters, and the most common injury was lung lobe perforation. Pericardium and mediastinum were also sites of injury. Some patients had small pleural effusions, with no other complications identified. CONCLUSION: Thoracic organ injury by percutaneous catheters may be more common than previously appreciated. Clinical and radiological findings are non-specific, and the diagnosis may not be apparent until autopsy.

The immunological properties of endoplasmic reticulum chaperones: a conflict of interest?

ER chaperones are abundant and highly conserved proteins that display both peptide binding and chaperone activity. Of the family of chaperones present in the mammalian ER, GRP94 and calreticulin are apparently unique in their ability to elicit CD8+ T-cell responses against components of their bound-peptide pools. The ability of GRP94 and calreticulin to elicit CD8+ T-cell responses indicates that both proteins bind peptides suitable for assembly on to MHC class-I molecules. The capacity to function as molecular chaperones and as peptide-binding proteins capable of transferring, directly or indirectly, peptides on to class-I molecules, indicates that GRP94 and calreticulin participate in the regulation of both peptide and polypeptide traffic in the ER. Perspectives on the regulation of and interplay between the peptide binding and chaperone activity of GRP94 and calreticulin are discussed.

Global cerebral blood flow, blood volume, and oxygen metabolism in patients with migraine headache.

OBJECTIVE: Migraine headaches with and without aura are representative of vascular headache states traditionally thought to be mediated by alterations in vascular tone. Validation of this theory has been hampered in part by technical difficulties inherent in the measurement of cerebral blood flow (CBF). The purpose of this study was to compare CBF measured during migraine and migraine-free states using PET. METHODS: Patients with a minimum of one migraine headache without aura per month (International Headache Society [IHS] criteria) underwent measurement of CBF, cerebral blood volume (CBV), oxygen extraction, and metabolism during an episode of spontaneous migraine headache. Imaging was repeated during a migraine-free period of at least 48 hours. PET radiotracers used were: CBF, H(2)15O; CBV, C15O; oxygen metabolism, 15O2. RESULTS: In nine patients (seven female and two male), global CBF (mL/min/100 g [SD]) was measured as 52.70 (6.9) during migraine and 59.65 (10.6) in the migraine-free state; p=0.028. CBV (mL/100 g [SD]) was 3.6 (0.43) during the symptomatic state and 3.8 (0.55) after the migraine; p=0.047. Oxygen metabolism (mL/min/100 g [SD]) was 3.68 (0.9) during migraine and 3.38 (1.02) without headache; p=0.211. The oxygen extraction ratio was 0.48 (0.15) and 0.41 (0.12) during migraine and migraine-free states, respectively; p=0.132. CONCLUSIONS: In patients experiencing migraine without aura, CBF and CBV are reduced during the headache phase. Cerebral oxygen metabolism and oxygen extraction are not significantly affected.

Permanent slide preparations of T lymphocyte-sheep red blood cell rosettes.

Rosette formation between sheep erythrocytes (SRBC) and human thymus-derived lymphocytes (T cells) is used to monitor T cells in various human diseases. Rosettes are usually counted in a hemacytometer immediately after preparation. This paper reports a technique for permanently fixing and staining rosettes for serial and comparative studies, a procedure which has probably been less well standardized, less reproducibly performed, and less widely used than many investigators appreciate. The technique describedhas the advantages of providing distinct morphological identification of the rosette-forming cell and it produces a permanent mount for further reference.

Single high dose-large field irradiation for palliation of advanced malignancies.

Single high dose-large field irradiation (SHD-LFI) has been used for palliation of symptoms secondary to widely disseminated malignancy. Fifty patients with various malignancies were treated with this technique in a private free-standing radiation therapy center between May 1982 and December 1984. Sixty-four treatments were delivered to the 50 patients. Thirty-two treatments were delivered to upper half-body fields, 15 to midbody, and 17 to thoracic fields. The most frequently used dose was 6 Gy which was used for 55 treatments. Thirty-nine patients had favorable response to treatment. All 22 patients with performance status (PS) 1-2 improved following treatment and 17 of 28 PS 3-4 improved. Only mild hematologic and gastrointestinal toxicity was seen. One case of possible radiation pneumonitis developed. It is concluded that SHD-LFI is a valuable palliative technique for general clinical use.

Protective immunity induced in squirrel monkeys with a multiple antigen construct against the circumsporozoite protein of Plasmodium vivax.

Saimiri boliviensis monkeys were immunized with a multiple antigen construct [(PvCS)2]2(P2)2 directed against the circumsporozoite protein of Plasmodium vivax or a combination of the multiple antigen construct with nonionic copolymer P1005, with P1005 and lipopolysaccharide, with muramyl tripeptide Mf-75, or with alum. Following intravenous challenge with 10,000 sporozoites of the Salvador I strain of P. vivax, 11 of the 26 monkeys were protected against patent parasitemia. Ten additional animals were partially protected. Following rechallenge of the 26 monkeys with 30,000 sporozoites of the homologous strain of parasite, four monkeys were totally protected and nine animals were partially protected.

Chaperone-mediated cross-priming: a hitchhiker's guide to vesicle transport (review).

The resident endoplasmic reticulum (ER) chaperone proteins GRP94 (gp96) and calreticulin can activate the immune system to slow or stop the progression of tumors by escorting tumor-derived peptides into the endogenous antigen presentation pathway of antigen presenting cells (APC). Although the phenomenology of cross-priming is well worked out, the mechanism(s) remains unclear. Continuing insights into cellular protein trafficking pathways suggest several means by which chaperones could travel from the extracellular space into the endosome, lysosome or ER of APC. In particular, proteins that cycle between two or more compartments and those that undergo and mediate retrograde flow offer models of how exogenous chaperones might travel in the APC. New insights into how non-chaperone proteins access the APC antigen presentation pathway also suggest several ways this process could occur.

Neuro-ophthalmological signs during rapid intravenous administration of phenytoin.

We prospectively studied eye movement after rapid intravenous administration of phenytoin. Nineteen healthy young adults participated in a study of i.v. phenytoin pharmacokinetics. Subjects received a standard dose of 15 mg/kg at a rate of 25 mg/min, and were examined neuro-ophthalmologically before and at the end of the infusion. All patients had horizontal gaze-evoked nystagmus (HGN), and impairment of horizontal smooth pursuit (SP). Other signs were present in the following percentages: vertical gaze-evoked nystagmus (16 19 ,84%), and impairment of vertical SP (15 19 , 79%). Total and free phenytoin levels did not directly correlate with the degree of any of the neurological signs tested. By review of the past studies of nystagmus during phenytoin therapy, we propose that nystagmus is present consistently during toxicity with initial phenytoin therapy, but occurs less consistently during ongoing phenytoin use or chronic toxicity.

The interactive model of psychotherapy.

The authors of this article present a new model of psychotherapy, the interactive model. The model is based on the assumptions that individual functioning is based not only on the cognitive, affective, and psychomotor (behavioral) domains but also on the interaction among these domains. This therapy model directs the clinician toward assessment and intervention of these interactions.

Non-immune hydrops fetalis caused by herpes simplex virus type 2 in the setting of recurrent maternal infection.

We report a case of non-immune hydrops fetalis (NIHF) caused by herpes simplex virus type 2 (HSV-2) in an infant whose mother had recurrent HSV-2 infection. In spite of prematurity, severe disseminated infection and hydrops, the infant survived and was neurologically intact. HSV-2-induced NIHF is extremely rare, particularly in the setting of recurrent maternal infection, and this case is, to our knowledge, the first report of a surviving infant. HSV-2 should be considered in the differential diagnosis of NIHF and early initiation of empiric acyclovir therapy is recommended in this setting, pending the results of virologic diagnostic tests.

Fluctuating and constant valproate administration gives equivalent seizure control in rats with genetic and acquired epilepsy.

PURPOSE: Controlled-release formulations of Valproate (VPA) reduce side effects by minimizing peak plasma VPA concentrations in patients with epilepsy. However, the impact of this on anti-seizure efficacy has not been thoroughly explored. Here the pharmacokinetics and pharmacodynamics of chronic intermittent (consequently, peak VPA concentrations) and continuous VPA administration were directly compared in two rat models of epilepsy. METHODS: Genetic Absence Epilepsy Rats from Strasbourg (GAERS) received a single acute bolus of VPA (100 mg/kg intravenously) combined with electroencephalography (EEG) and/or blood sampling for 180 min post-injection. GAERS and epileptic rats post-kainic acid-induced status epilepticus were chronically infused intravenously (3-5 days, respectively) with (i) saline followed by in random order (ii) intermittent and (iii) continuous VPA (42 mg/kg/h), separated by two days of wash-out. Seizures were quantified using video-EEG monitoring and VPA levels measured in brain, cerebrospinal fluid and plasma. RESULTS: Following acute VPA administration seizure suppression in GAERS persisted after plasma VPA levels became very low. Chronic intermittent and continuous VPA significantly suppressed seizures in both models (p<0.01) with no difference between administration regimens. In GAERS, the pattern of seizure suppression during intermittent treatment was constant, in contrast to the fluctuating VPA plasma and brain levels. There was discordance between the temporal pattern of plasma, brain VPA levels and seizure suppression efficacy in GAERS. CONCLUSION: Administration regimes that result in fluctuating VPA blood levels achieve equivalent sustained seizure suppression as those that maintain steady mid-range concentrations.