Relevance of spontaneous activity to urinary bladder function: an in vitro and in vivo study

The presence and functional significance (if any) of spontaneous activity in the normal urinary bladder during filling is a controversial subject. One model used by many investigators to study spontaneous activity has been isolated urinary bladder smooth muscle strips. Although spontaneous activity is a property commonly observed in isolated urinary bladder strip preparations, the in vitro whole bladder preparation (rabbit) is devoid of spontaneous activity. Additionally, under normal conditions the in vivo rabbit bladder does not display spontaneous activity during the filling phases of micturition. The present study compares the spontaneous activity of isolated smooth muscle strips, the whole bladder preparation, and the catheterized in vivo bladder (rabbit). The results are as follows: The spontaneous activity (frequency and amplitude) of isolated strips is extremely variable among strips of the same bladder. Spontaneous activity is not affected by the following specific inhibitory compounds: tetrodotoxin, atropine, phentolamine, propranolol and hexamethonium. This indicates that spontaneous activity observed in isolated strips is myogenic in nature and not dependent on the activation of specific autonomic receptors. The in vitro whole bladder preparation shows no spontaneous activity at any volume or pressure unless longitudinal tension is applied. The spontaneous activity of the whole bladder subjected to longitudinal tension is not affected by the same compounds mentioned above. Spontaneous activity of the in vivo bladder is absent at low intravesical volumes and pressures. Spontaneous activity develops upon reaching a critical pressure. However, this activity is completely inhibited by intravenous ganglionic blockade (hexamethonium). In the presence of hexamethonium, the in vivo bladder is devoid of spontaneous activity at any volume or pressure, thus the in vivo "spontaneous activity" is mediated through neuronal reflexes. It is concluded that under normal circumstances the rabbit bladder is devoid of myogenic spontaneous activity and that the spontaneous activity observed in isolated strips is directly related to longitudinal stretch. Since under normal conditions the bladder is not subjected to longitudinal stretch, the spontaneous activity observed in the isolated strip studies has little physiological significance under normal conditions, but could help explain the pathophysiology of certain dysfunctions during the filling stage of micturition.     

Phonomicrosurgery for benign vocal Fold lesions - our experience

Benign lesions of glottis creates stiffness of the vocal fold and inefficient glottal valve, aerodynamically effecting the vocal quality by preventing smooth vocal edge closure. Introduction of phonomicrosurgical techniques based on Hirano ’s principle of vocal fold epithelium have revolutionized results of voice surgery. Our experience in the management of benign vocal fold lesions by phonomicrosurgical techniques with pre and post operative stroboscopic, perceptual and computerized acoustic voice analysis is described.     

Assessment of oral bioavailability and preclinical pharmacokinetics of DRF-6196, a novel oxazolidinone analogue, in comparison to linezolid.

The aim of this study was to determine the bioavailability of a novel oxazolidinone, DRF-6196, in mice and rats following intravenous (i.v) and oral dosing and to compare the pharmacokinetics with those obtained following linezolid dosing. Blood samples were drawn at predetermined intervals up to 24 h post-dose after either DRF-6196 or linezolid administration. The concentrations of DRF-6196 and linezolid in various plasma samples were determined by a HPLC method. Following oral administration maximum concentrations of DRF-6196 were achieved within 0.5 h irrespective of the species. While the doses increased in the ratio of 1 : 3 : 10, mean Cmax and AUC(0-infinity) values in mice for DRF-6196 increased in the ratio of 1 : 3.87 : 8.53 and 1 : 2.51 : 9.24, respectively. Both the Cmax and AUC(0-infinity) values increased almost proportional to the dose administered in mice. Following i.v administration, the concentration of DRF-6196 declined in a bi-exponential fashion with terminal elimination half-life of 1.5 h irrespective of the species. The systemic clearance and volume of distribution of DRF-6196 in mice were 1.14 L/h/kg and 0.66 L/kg, respectively after i.v administration, while the respective values in rats were 0.61 L/h/kg and 0.41L/kg, respectively. Elimination half-life ranged between 0.8-1.5 h. Absolute oral bioavailability of DRF-6196 was found to be 80-96% across the test dose range. Although plasma levels of DRF-6196 were lesser compared to linezolid in the initial hours, it may not have any consequences on the clinical effectiveness of the molecule.     

Predictors of aneurysm occlusion following treatment with the WEB device: systematic review and case series

The Woven EndoBridge (WEB) device is becoming increasingly popular for treatment of wide-neck aneurysms. As experience with this device grows, it is important to identify factors associated with occlusion following WEB treatment to guide decision making and screen patients at high risk for recurrence. The aim of this study was to identify factors associated with adequate aneurysm occlusion following WEB device treatment in the neurosurgical literature and in our case series. A systematic review of the present literature was conducted to identify studies related to the prediction of WEB device occlusion. In addition, a retrospective review of our institutional data for patients treated with the WEB device was performed. Demographics, aneurysm characteristics, procedural variables, and 6-month follow-up angiographic outcomes were recorded. Seven articles totaling 450 patients with 456 aneurysms fit our criteria. Factors in the literature associated with inadequate occlusion included larger size, increased neck width, partial intrasaccular thrombosis, irregular shape, and tobacco use. Our retrospective review identified 43 patients with 45 aneurysms. A total of 91.1% of our patients achieved adequate occlusion at a mean follow-up time of 7.32 months. Increasing degree of contrast stasis after WEB placement on the post-deployment angiogram was significantly associated with adequate occlusion on follow-up angiogram (p?=?0.005) and with Raymond-Roy classification (p?=?0.048), but not with retreatment (p?=?0.617). In our systematic review and case series totaling 450 patients with 456 aneurysms, contrast stasis on post-deployment angiogram was identified as a predictor of adequate aneurysm occlusion, while morphological characteristics such as larger size and wide neck negatively impact occlusion.

     

A phase I clinical and pharmacokinetic study of the dolastatin analogue cemadotin administered as a 5-day continuous intravenous infusion

Purpose: The dolastatins are a class of naturally occurring cytotoxic peptides which function by inhibiting microtubule assembly and tubulin polymerization. Cemadotin is a synthetic analogue of dolastatin 15 with potent antiproliferative and preclinical antitumor activity. This report describes a phase I study to evaluate the administration of cemadotin to adult cancer patients by a 5-day continuous intravenous (CIV) infusion. Methods: All patients had histologically confirmed refractory solid tumors. The dose was escalated from an initial level of 2.5 mg/m² (0.5 mg/m² daily) according to a modified Fibonacci algorithm. A minimum of three patients was evaluated at each dose level until the maximum tolerated dose (MTD) was established. Treatment was repeated every 21 days until patients were removed from the study due to toxicity or disease progression. Drug-related toxicities were evaluated and graded by the U.S. National Cancer Institute's Common Toxicity Criteria. A radioimmunoassay (RIA) that detected both the parent drug and its metabolites with an intact N-terminal region of the molecule was used for pharmacokinetic studies. Results: Twenty heavily pretreated patients received a total of 40 courses of cemadotin over five dose levels ranging from 2.5 to 17.5 mg/m². Reversible dose-related neutropenia was the principal dose-limiting toxicity and 12.5 mg/m² was established as the MTD. Nonhematologic toxicities attributed to the drug were moderate, and there was no evidence of the cardiovascular toxicity noted in the prior phase I studies of cemadotin given IV as a 5-min injection or 24-h infusion. There were no objective antitumor responses. Time courses of the cemadotin RIA equivalent concentration in whole blood were defined in 14 patients during the first cycle of therapy. The RIA-detectable species exhibited apparent first-order pharmacokinetics across the entire range of doses. The mean ± SD of the observed steady-state blood concentration at the 12.5 mg/m² MTD was 282 ± 7 nM (n=3). Blood levels decayed monoexponentially following the end of the infusion, with a mean half-life of 13.2 ± 4.3 h (n=14) in all patients. Mean values (n=14) of the total blood clearance and apparent volume of distribution at steady state were 0.52 ± 0.09 l/h/m² and 9.9 ± 3.3 l/m², respectively. Conclusions: The cardiotoxic effects of cemadotin were completely avoided by administering it as a 120-h CIV infusion. Thus, cardiovascular toxicity appears to be associated with the magnitude of the peak blood levels of the parent drug or its metabolites, whereas myelotoxicity is related to the duration of time that blood levels exceed a threshold concentration. Nevertheless, the data acquired during the extensive clinical experience with cemadotin requires careful examination to assess whether advancing this compound into disease-oriented efficacy studies is merited. Received: 8 November 1999 / Accepted: 28 April 2000     

Efficacy,pharmacokinetic, and safety assessment of adalimumab,a fully human anti-tumor necrosis factor-alpha monoclonal antibody,in adults with rheumatoid arthritis receiving concomitant methotrexate: a pilot study

BACKGROUND: Because traditional therapies for rheumatoid arthritis (RA) such as methotrexate (MTX) do not produce an adequate response in many patients, newer therapies that block the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) are increasingly being used in combination with MTX. OBJECTIVE: This study evaluated the efficacy, pharmacokinetics, and safety profile of adalimumab, a fully human anti-TNF alpha monoclonal antibody, when added to continuing MTX therapy. METHODS: This Phase I, randomized, dose-titration study consisted of a 4-week, double-blind, placebo-controlled treatment phase and a 26-month, open-label continuation phase. Patients with RA who had been taking stable doses of MTX (mean dose, 17 mg/wk) for > or =3 months before enrollment with an inadequate response were randomly assigned to receive 2 single doses of either adalimumab 0.25, 0.5, 1, 3, or 5 mg/kg i.v. or placebo in the double-blind phase. In the open-label phase, patients received treatment with 1 of the doses of adalimumab every other week or monthly for 18 months; patients were then switched to adalimumab 40 mg i.v. or SC every other week or monthly. The main efficacy end point was 20% improvement in American College of Rheumatology response criteria (ACR20). Other efficacy end points included 50% (ACR50) and 70% improvements in ACR response criteria. Pharmacokinetic parameters were analyzed for adalimumab and MTX during both phases of the study. Serum adalimumab concentrations were analyzed using a validated enzyme-linked immunosorbent assay relying on the double-antigen principle. Peak and trough concentrations were determined from observed concentration-time data, and a modeling approach was used to estimate total serum clearance, mean apparent terminal half-life, apparent volume of distribution at steady state, and area under the concentration-time curve. RESULTS: Sixty patients entered the double-blind phase, 45 receiving adalimumab and 15 receiving placebo; 1 placebo recipient chose not to continue into the open-label phase. Overall, the study population included 47 (78.3%) women and 13 (21.7%) men. The mean age was 52.9 years (range, 24-73 years), and the mean body weight was 69.7 kg (range, 43-98 kg). ACR20 and ACR50 responses were achieved on at least 1 assessment during the 4-week double-blind phase by a respective 29 (64.4%) and 11 (24.4%) of 45 patients receiving active treatment and by 4 (26.7%) and none of the 15 patients receiving placebo. Responses to adalimumab were rapid, with 10 (22.2%) of 45 patients achieving an ACR20 response within 24 hours of dosing. Of 29 adalimumab recipients who had an ACR20 response, 18 (62.1%) had a duration of response (time from first occurrence of a response to first occurrence of a nonresponse) of 1 to 2 weeks, and 11 (37.9%) had a duration of response of 3 to 13 weeks. The pharmacokinetic properties of adalimumab appeared to be linear. The mean apparent terminal half-life after a single intravenous dose of adalimumab ranged from 15 to 19 days in the 5 dose groups. Repeated administration of adalimumab had no statistically significant effect on the pharmacokinetics of MTX, indicating that dose adjustment of MTX is not necessary. Adalimumab was well tolerated, and there were no dose-related adverse events. CONCLUSIONS: Among patients with active RA who had not had an adequate response to MTX, addition of adalimumab to MTX achieved statistically significant, long-term improvement compared with placebo plus MTX (P < or = 0.05), as indicated by ACR responses at 26 months. The combination was well tolerated. Adalimumab exhibited linear pharmacokinetics. In this selected patient population, adalimumab's long half-life of 15 to 19 days supports every-other-week dosing. Coadministration of adalimumab did not alter serum levels of MTX.     

Harmonization of regulatory approaches for evaluating therapeutic equivalence and interchangeability of multisource drug products: workshop summary report

Regulatory approaches for evaluating therapeutic equivalence of multisource (or generic) drug products vary among different countries and/or regions. Harmonization of these approaches may decrease the number of in vivo bioequivalence studies and avoid unnecessary drug exposure to humans. Global harmonization for regulatory requirements may be promoted by a better understanding of factors underlying product performance and expectations from different regulatory authorities. This workshop provided an opportunity for pharmaceutical scientists from academia, industry and regulatory agencies to have open discussions on current regulatory issues and industry practices, facilitating harmonization of regulatory approaches for establishing therapeutic equivalence and interchangeability of multisource drug products.