A Pharmacokinetic/Pharmacodynamic Approach to Predict Total Prednisolone Concentrations in Human Plasma

Prednisolone and prednisone are two widely used corticosteroids for various inflammatory and immune diseases. Prednisolone is the active form of prednisone in vivo. Total prednisolone in plasma exhibits nonlinear pharmacokinetics mainly due to its nonlinear protein binding. Other factors such as reversible metabolism (or interconversion between prednisolone and prednisone), competitive protein binding from endogenous cortisol, cortisol circadian rhythm, and prednisolone mediated cortisol suppression complicate prednisolone pharmacokinetics. This study was aimed to develop a new approach to describe the nonlinear pharmacokinetics of total prednisolone and predict total prednisolone concentrations in plasma. Based on literature datasets, a linear two-compartment pharmacokinetic model was developed to adequately describe the reversible metabolism between free prednisone and prednisolone. Cortisol and prednisolone protein binding were described via the sum of a Langmuir and linear type binding. The endogenous cortisol circadian rhythm and cortisol suppression during prednisone or prednisolone exposure were described with a previously reported linear release rate pharmacokinetic/pharmacodynamic (PK/PD) model. By combining the pharmacokinetic models for free prednisone and prednisolone, the linear release rate model for cortisol suppression, and competitive protein binding between cortisol and prednisolone, we were able to predict total prednisolone concentrations in plasma. The predicted total prednisolone concentrations in plasma were in good agreement with the literature reported data. Thus, this PK/PD approach shows that the combination of nonlinear protein binding, cortisol circadian rhythm, and cortisol suppression could account for the nonlinearity of total prednisolone. In addition, it also allows a valid prediction of total prednisolone in plasma after either prednisone or prednisolone administration.

Switching from tacrolimus to sirolimus halts the appearance of new sebaceous neoplasms in Muir-Torre syndrome

Little is known about the effects of immunosuppression on patients with hereditary nonpolyposis colorectal cancer (HNPCC). We describe a kidney transplant recipient with unrecognized Muir-Torre syndrome in whom the administration of a tacrolimus-based regimen led to the eruption of multiple sebaceous tumors. The patient was later found to harbor an MSH2 mutation. Switching to a sirolimus-based regimen resulted in arrest of the disease. When the patient was switched back to tacrolimus, new facial lesions rapidly appeared. Switching again to sirolimus resulted again in halting the appearance of new lesions. This finding is in line with the known antiangiogenic activity of sirolimus and reports on the regression of cutaneous Kaposi's sarcoma in kidney transplant recipients switched from another immunosuppressive regimen to sirolimus. Further studies on the potential use of sirolimus for the treatment of de novo tumors in immunosuppressed kidney transplant recipients with HNPCC are warranted.

Aviäre Influenza und das Schwere Akute Respiratorische Syndrom (SARS) - Erfahrungen und Perspektiven

New respiratory viruses associated with pneumonia have in the past few years been detected in humans. The sudden appearance of the severe acute respiratory syndrome (SARS) in 2003 demonstrated that an emerging and highly infectious disease caused by a hitherto unknown virus was able to spread rapidly, but could finally be contained by stringent measures. The avian influenza A-H5N1-virus of high pathogenicity has crossed in multiple instances the species barriers between humans, mammals, and birds posing a serious pandemic threat. The application of the so far learnt and the continued development of preventive strategies, efficient vaccines, and antiviral substances are besides worldwide surveillance decisive to rapidly detect the repeated, enforced, or new appearance of viruses like the SARS-CoV, influenza A-H5N1 virus, or of new viruses, to contain their spread, and to defeat them.

[Guillain-Barrè syndrome and inadequate antidiuretic hormone secretion syndrome]

Several neurologic disorders including Guillain-Barré syndrome (GBS) are associated with hyponatremia. Hyponatremia and its overly fast correction have major implications to the course of the underlying neurologic disease. We report a case of GBS complicated by hyponatremia secondary to the development of inadequate antidiuretic hormone secretion syndrome. Differential diagnosis, pathophysiology, and therapeutic approach of hyponatremia in association with GBS are discussed.

Levels of PBDEs, PCDDs, PCDFs, and coplanar PCBs in edible fish from California coastal waters

The levels of polychlorinated dibenzo-dioxins (PCDDs), polychlorinated dibenzo-furans (PCDFs), coplanar polychlorinated biphenyls (coPCBs), and polybrominated diphenyl ethers (PBDEs) were measured in fish collected from San Francisco Bay in 2000 and from the California coast in 2001. The samples were composites of only the edible portions of the fish (skin on, skin off, or whole body minus head and guts) of comparable size and from distinct geographical areas. Sixty-five composite samples were analyzed for PCDD/PCDF/coPCBs, and 43 composite samples were analyzed for PBDEs. For all fish of all species from all sampling areas, the mean concentration of the sum of BDEs 47, 99, 100, 153, and 154 was 302 ng/g lipid weight, with BDE 47>100>99 approximately 154>153. For all fish of all species from all sampling areas, the mean PCDD/PCDF International Toxic Equivalent (I-TEQ) was 33.1 pg/g lipid. For the three coPCBs (77, 126, 169), the mean I-TEQ for all fish of all species from all sampling areas was 109 pg/g lipid. The highest concentrations of both PCDD/PCDF/coPCBs and PBDEs were found in the highly populated areas of San Francisco Bay, the Los Angeles area, and San Diego Bay.

Novel truncating and missense mutations of the KCC3 gene associated with Andermann syndrome

Background: Andermann syndrome (OMIM 218000) is an autosomal recessive motor-sensory neuropathy associated with developmental and neurodegenerative defects. The cerebral MRI reveals a variable degree of agenesis of the corpus callosum. Recently, truncating mutations of the KCC3 gene (also known as SLC12A6) have been associated with Andermann syndrome.

Methods: The authors assessed clinically and genetically three isolated cases from Germany and Turkey with symptoms consistent with Andermann syndrome.

Results: The authors detected four novel mutations within the KCC3 gene in their patients: two different truncating mutations in the first patient, a homozygous truncating mutation in the second, and a homozygous missense mutation in the third patient. In contrast to the classic phenotype of the Andermann syndrome linked to truncating KCC3 mutations the phenotype and the course of the disease linked to the missense mutation appeared to be different (i.e., showing additional features like diffuse and widespread white matter abnormalities).

Conclusions: Not only truncating but also missense mutations of the KCC3 gene are associated with Andermann syndrome. Different types of KCC3 mutations may determine different clinical phenotypes.

Further clinical and genetic characterization of SPG11: hereditary spastic paraplegia with thin corpus callosum

Hereditary spastic paraplegias (HSPs) are a heterogeneous group of neurodegenerative disorders leading to progressive spasticity of the lower limbs. Clinically, HSPs are divided into "pure" and "complicated" forms. In pure HSP, the spasticity of the lower limbs is the sole symptom, whereas in complicated forms additional neurological and non-neurological features are observed. Genetically, HSPs are divided into autosomal dominant (AD), autosomal recessive (AR) and X-linked (XL) forms. Up to date, 30 different HSPs are linked to different chromosomal loci and 11 genes could be defined for AR-HSP, AD-HSP and XL-HSP. SPG11, an AR-HSP (synonym: HSP11), is a complicated HSP associated with a slowly progressive spastic paraparesis, mental impairment and the development of a thin corpus callosum (TCC) during the course of the disease. SPG11 has been previously linked to chromosomal region 15q13 - 15. First, we applied rigid diagnostic criteria to systematically examine 20 Turkish families with autosomal recessive HSP for characteristic features of SPG11. We detected four large Turkish families with AR-HSP and TCC consistent with SPG11. Subsequent genetic linkage analysis of those 4 families refines the SPG11 locus further down to a small region of 2.93 cM with a maximum lod score of 11.84 at marker D15S659 and will guide further candidate gene analysis.

Calcified neurocysticercosis lesions trigger symptomatic inflammation during antiparasitic therapy

We report a patient with neurocysticercosis who developed numerous cerebral edematous lesions while undergoing cysticidal therapy. These lesions outnumbered viable cystic lesions seen before therapy. Most new lesions were subsequently found to be associated with former calcifications not seen on initial MR imaging. Calcified neurocysticercosis lesions can trigger inflammatory reactions during therapy, and the number and location of calcified neurocysticercosis lesions may influence treatment decisions.