We studied the mechanisms involved in the translocation of human calcitonin (hCT) through excised bovine nasal mucosa (net mucosal-to-serosal permeability approximately 10(-)5 cm s-1). To determine structural requirements for the suggested vesicular internalization two carboxyfluorescein-labeled (fl) hCT fragments, the C-terminal fragment [Nalpha-fl]hCT(9-32) and the N-terminal fragment [Lys(fl)18]hCT(1-24) were synthesized. In presence of the endocytosis inhibitor cytochalasin D mucosal-to-serosal and serosal-to-mucosal hCT permeabilities were equal. Pathway visualization by confocal laser scanning microscopy showed punctated fluorescence indicating vesicular internalization of both hCT and [Nalpha-fl]hCT(9-32). In contrast, the N-terminal fragment lacking the beta-sheet forming C-terminus (25-32) was not internalized. Circular dichroism showed that, when interacting with neutral and negatively charged liposomes, hCT adopts beta-sheet conformation. In a concentrated aqueous solution, beta-sheet formation induces hCT self-assembly and fibrillation. High partitioning of hCT into lipid bilayer membranes was reflected by an apparent partition coefficient log D(pH 7.4) = 2.5 (liposome-buffer equilibrium dialysis). We propose that the high lipid partitioning and beta-sheet formation result in C-terminus-restricted supramolecular self-assembly of hCT and [Nalpha-fl]hCT(9-32) in lipid membranes. Vesicular internalization is suggested to be associated with self-assembly induced perturbation of the lipid bilayer. Condensed hCT self-assemblies may explain the high capacity of net mucosal-to-serosal hCT permeation, which compares favorably with the low transport capacity of receptor-mediated endocytosis.

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IntroductionOne in three Danish children under 3 years of age experience asthma-like symptoms, and one-third will later be diagnosed with asthma. Oral prednisolone is used in various formulations to treat acute asthma. However, the potential differences in bioequivalence between these formulations have never been examined in children despite interchangeable use in clinical practice.Methods and analysisAn open-label, randomised, two-treatment cross-over trial investigating the bioequivalence of different prednisolone formulations in children with airway disease.The included patients (6 months–11 years of age) are admitted to the Department of Paediatric and Adolescent Medicine Nordsjællands University Hospital, Hillerød, with asthma or asthma-like symptoms.The primary objective is to assess the bioequivalence between different prednisolone formulations herein area under the concentration time curve, Cmax and Tmax using saliva samples. The secondary objectives are to evaluate tolerability (five-point face scale), adverse events and severity of the disease. If the patient has an intravenous access for other purposes, the saliva samples will be validated with plasma samples.A total of 66 evaluable patients are needed according to European Medicines Agency Guideline on bioequivalence.Ethics and disseminationTraditional pharmacokinetic trials are burdensome due to the extent of blood samples necessary to capture the time-dependant drug profile. Saliva sampling is far more acceptable for paediatric patients. In addition, this trial adheres to standard dosing strategies. No additional venepunctures are performed, and no additional prednisolone doses are administered.Guidelines for paediatric bioequivalence trials are warranted.Trial registration numberThe Danish Medicines Agency EudraCT: 2017-003590-33, The Ethics Committee case no: H-17027252, and the Danish Data Protection Agency: BFH-2017–103, I-Suite no.: 05935.

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Increase in permeability at high TP concentrations involves competitive enzyme saturation combined with self-enhanced paracellular permeation.

Treatment strategies for asthma-like symptoms are challenging with no international consensus on dose of systemic glucocorticoids. Despite, asthma-like symptoms remain one of the most common medical conditions seen in infants and preschool children. This is further complicated by limited licensed preparations and use of various extemporaneously prepared formulations in some countries. In Denmark, all extemporaneous formulations are produced according to GMP, which is different from other European countries. This retrospective cohort study examined the type and dose of extemporaneously prepared glucocorticoid formulations prescribed to infants and preschool children 0-5 years of age with acute asthma-like symptoms over a three-year period at three paediatric departments in the Capital Region of Denmark covering 1.8 mill inhabitants. In total 4877 patients were screened for eligibility. In addition, length of hospitalisation, prescribed co-medication, readmission, and adverse events were registered. Almost one in ten of the patients were treated with extemporaneous prednisolone. Eight different formulations were used interchangeably despite lack of studies supporting therapeutic equivalence between these formulations. Further, a higher dose did not result in shorter hospitalisation.