Extemporaneous Suspension of Propafenone: Attending Lack of Pediatric Formulations in Mexico

Background Physicians have frequently encountered difficulties when prescribing drugs not available in doses suitable for pediatric age groups. Furthermore, children have difficulty swallowing tablets. This study aimed to determine the stability of an oral propafenone suspension made from commercial tablets with a syrup vehicle and to establish its reliable use with children. Methods An extemporaneous suspension of propafenone 1.5 mg/ml was prepared with commercial tablets. Its physicochemical and microbiologic stability was established by constant monitoring during 90 days at room temperature (15 ± 5°C) and at refrigeration (3–5°C). Plasma levels of propafenona were measured in two children with supraventricular tachycardia at steady state. Results The suspension was stable, maintaining its original physicochemical and microbiologic properties. Moreover, no apparent changes in color or odor were observed. Plasma levels of propafenone in patients demonstrated therapeutic concentrations after they had taken the suspension, with no unwanted outcome. Conclusions The conservation of both physicochemical and microbiologic stability of the suspension represents an option for the administration of propafenone to children. Presented in part at the 35th Annual Meeting of American College of Clinical Pharmacology, Cambridge MA, 16–19 September 2006. Laboratorio de Farmacología, Instituto Nacional de Pediatría.     

Autoproteolytic cleavage mediates cytotoxicity of <Emphasis Type="Italic">Clostridium difficile</Emphasis> toxin A

Toxin A and toxin B from Clostridium difficile are the causative agents of the antibiotic-associated pseudomembranous colitis. They are of an A/B structure type and possess inositol hexakisphosphate-inducible autoproteolytic activity to release their glucosyltransferase domain to the cytoplasm of target cells. In this study, we investigated the effect of extracellular and intracellular autoproteolytic cleavage on the function of TcdA. Extracellular cleavage led to functional inactivation albeit TcdA was less susceptible to inositol hexakisphosphate-induced autoproteolysis than TcdB. A non-cleavable TcdA mutant (TcdA A541 G542 A543) was generated to investigate whether autoproteolysis is a prerequisite for intracellular function of TcdA. Although the EC₅₀ regarding cell rounding was about 75-fold reduced in short-term assay, non-cleavable TcdA was able to induce complete cell rounding and apoptosis after 36 h comparable to wildtype TcdA when continuously present. Studies with limited uptake of toxins revealed progressive Rac1 glucosylation and complete cell rounding for TcdA, whereas the effect induced by non-cleavable TcdA was reversible. These findings argue for cytosolic accumulation of the released glucosyltransferase domain of wild-type TcdA and rapid degradation of the non-cleavable TcdA. In summary, extracellular cleavage functionally inactivates TcdA (and TcdB), whereas intracellular autoproteolytic cleavage is not essential for function of TcdA but defines its potency.     

Stress-induced sensitization of the hypothalamic-pituitary adrenal axis is associated with alterations of hypothalamic and pituitary gene expression

We have previously reported that inescapable tail shock (IS) produces persistent changes in hypothalamic-pituitary-adrenal (HPA) axis function. These changes are manifest as an elevation in basal corticosterone (CORT) levels, a sensitization of adrenocorticotropin hormone (ACTH) and CORT responses to subsequent challenge, and a failure of dexamethasone to suppress both the ACTH and CORT responses to a subsequent challenge. The experiments presented here examine IS-induced alterations in the responsiveness of the HPA axis, particularly at the level of the anterior pituitary. The data presented show that adrenalectomy does not abolish the IS-induced sensitization of the HPA axis, suggesting that the sensitization is not solely caused by a defect in glucocorticoid negative feedback. Analysis of gene expression in the anterior pituitary revealed that IS exposure persistently elevated basal levels of proopiomelanocortin (POMC; the precursor to ACTH) mRNA and sensitized the POMC hnRNA and c-fos mRNA response to a subsequent challenge. Analysis of gene expression in the parvocellular division of the paraventricular nucleus of the hypothalamus (pPVN) after IS exposure revealed that basal levels of corticotropin-releasing hormone (CRH) mature mRNA are elevated and the c-fos mRNA response to a subsequent challenge is enhanced. Finally, a blunted in vitro ACTH response to CRH challenge is observed after IS exposure. These data suggest that the ultimate source of the IS-induced sensitization is not the anterior pituitary and implicate an increased drive on the anterior pituitary from the pPVN.     

A systematic review of duloxetine and venlafaxine in major depression,including unpublished data

Schueler Y‐B, Koesters M, Wieseler B, Grouven U, Kromp M, Kerekes MF, Kreis J, Kaiser T, Becker T, Weinmann S. A systematic review of duloxetine and venlafaxine in major depression, including unpublished data. Objective: To determine the short‐term antidepressant efficacy and tolerability of duloxetine and venlafaxine vs. each other, placebo, selective serotonin reuptake inhibitors (SSRIs), and tri‐ and tetracyclic antidepressants (TCAs) in adults with major depression. Method: Meta‐analysis of randomised controlled trials identified through bibliographical databases and other sources, including unpublished manufacturer reports. Results: Fifty‐four studies including venlafaxine arms (n = 12 816), 14 including duloxetine arms (n = 4528), and two direct comparisons (n = 836) were analysed. Twenty‐three studies were previously unpublished. In the meta‐analysis, both duloxetine and venlafaxine showed superior efficacy (higher remission and response rates) and inferior tolerability (higher discontinuation rates due to adverse events) to placebo. Venlafaxine had superior efficacy in response rates but inferior tolerability to SSRIs (OR = 1.20, 95% CI 1.07–1.35 and 1.38, 95% CI 1.15–1.66, respectively), and no differences in efficacy and tolerability to TCAs. Duloxetine did not show any advantages over other antidepressants and was less well tolerated than SSRIs and venlafaxine (OR = 1.53, 95% CI 1.10–2.13 and OR 1.79, 95% CI 1.16–2.78, respectively). Conclusion: Rather than being a first‐line option, venlafaxine appears to be a valid alternative in patients who do not tolerate or respond to SSRIs or TCAs. Duloxetine does not seem to be indicated as a first‐line treatment.     

Dysregulation of Mucosal Membrane Transporters and Drug-Metabolizing Enzymes in Ulcerative Colitis

Intestinal transporters and metabolizing enzymes are the important factors of the intestinal absorption barrier. Because there is evidence that their expression and function may be affected during inflammatory conditions, we investigated gene expression, protein abundance, and regulation of relevant intestinal transporters and metabolizing enzymes in the intestinal mucosa of patients with ulcerative colitis (UC). Specimens from inflamed and noninflamed tissues of 10 patients with UC as well as colonic control tissues of 10 patients without inflammation were subjected to gene (9 enzymes, 15 transporters, 9 cytokines) and microRNA (N = 54) expression analysis. Protein abundance was quantified by liquid chromatography-tandem mass spectrometry–based targeted proteomics. Gene expression of several metabolizing enzymes (e.g., CYP2C9, UGT1A1) and transporters such as ABCB1 (ABCB1), ABCG2 (ABCG2), and monocarboxylate transporter 1 (MCT1, SLC16A1) were significantly decreased during inflammation and negatively correlated to microRNAs. On contrary, multidrug resistance-protein 4 (MRP4, ABCC4), organic anion–transporting polypeptide 2B1 (OATP2B1, SLCO2B1), and organic cation transporter-like 2 (ORCTL2, SLC22A18) were significantly elevated in inflamed tissue. However, at protein level, these findings could only be confirmed for MCT1. UC is associated with complex changes in the intestinal expression of enzymes, transporters, cytokines, and microRNAs, which may affect efficacy of anti-inflammatory drug therapy or the disease state itself.     

Cholecystokinin peptides in the brain and pituitary of the bullfrog Rana catesbiana: distribution and characterization

The distribution of CCK peptides in the bullfrog brain was determined with a CCK radioimmunoassay. Frog brain CCK distribution resembles rat, porcine, and human brain in that CCK concentration is moderate to high in hypothalamus, diencephalon, and medulla (3–18.4 ng /protein) and low in cerebellum (0.6 ng/mg protein). However, unlike all mammalian species examined, the CCK content of frog cerebral cortex, hippocampus and olfactory lobe is quite low (0.03–0.23 ng/mg protein).The elution of CCK-like peptides in frog brain extracts was determined on two HPLC systems. On both systems the bulk of the CCK-like material eluted with CCK8 sulfate and separated from gastrin and other CCK peptides.These data suggest that though the chemical structure of CCK appears to be the same in the brains of frogs and mammals, the distribution of CCK in the brain appears to have shifted during the course of evolution, becoming a cortical, hippocampal, and olfactory system peptide only in more evolved organisms.     

Clinical evidence of an interaction between imipramine and acetylsalicylic acid on protein binding in depressed patients

The binding of imipramine to plasma proteins was studied in 20 adult patients with endogenous depression, with the purpose of assessing the effect produced by its simultaneous administration with an analgesic. Patients were administered 150 mg/day imipramine for 5 days and the binding to plasma proteins was determined. This was repeated 2 days later, after simultaneous administration of imipramine with 1,000 mg/day acetylsalicylic acid (ASA). Adverse effects for each patient were registered during both phases and were classified as mild, moderate, or severe. Results showed 84.4 +/- 7.07% of imipramine bound to plasma proteins and 72.18 +/- 6.5% when imipramine was administered with ASA (p < 0.05). When imipramine was administered alone, 1.95 mild adverse events per patient were registered. When imipramine was administered with ASA, the mild adverse events increased to 3.1 (p < 0.01) and the severe adverse events increased from 0.6 to 1.5 (p < 0.01). The levels of free imipramine increased when ASA was administered, indicating a displacement on the binding to plasma proteins. When adverse events were compared for each treatment, the accumulation of the free fraction of imipramine caused an increase in adverse events as well as in their clinical severity.