Sample size determination in bioequivalence studies using statistical assurance.

AIMS: Bioequivalence (BE) trials aim to demonstrate that the 90% confidence interval of the T/R-ratio of the pharmacokinetic metrics between two formulations (test [T] and reference [R]) of a drug is fully included in the acceptance interval [0.80, 1.25]. Traditionally, the sample size of BE trials is based on a power calculation based on the intrasubject variability coefficient of variation (CV) and the T/R-ratio of the metrics. Since the exact value of the T/R-ratio is not known prior to the trial, it is often assumed that the difference between the treatments does not exceed 5%. Hence, uncertainty about the T/R-ratio is expressed by using a fixed value for the sample size calculation. We propose to characterise the uncertainty about the T/R-ratio by a (normal) distribution for the log(T/R-ratio), with an assumed mean of  log Î¸ = 0.00 (i.e. θ = 1.00) and a standard deviation σu , which quantifies the uncertainty. Evaluating this distribution leads to the statistical assurance of the BE trial. METHODS: The assurance of a clinical trial can be derived by integrating the power over the distribution of the input parameters, in this case, the assumed distribution of the log(T/R)-ratio. Because it is an average power, the assurance can be interpreted as a measure of the probability of success that does not depend on a specific assumed value for the log(T/R)-ratio. The relationship between power and assurance will be analysed by comparing the numerical outcomes. RESULTS: Using the assurance concept, values of the standard deviation for the distribution of potential log(T/R)-ratios can be chosen to reflect the magnitude of uncertainty. For most practical cases (i.e. when 0.95 ≤ Î¸ ≤ 1.05), the sample size is not, or only slightly, changed when σ = |log(θ)|. CONCLUSION: The advantage of deriving the assurance for BE trials is that uncertainty is directly expressed as a parameter of variability.

Cytochrome c oxidase deficiencies in the muscle of patients with inflammatory myopathies.

We studied mitochondrial function in inflammatory myopathies, using cytochrome c oxidase (COX) reaction on muscle biopsy samples from 30 patients (15 with dermatomyositis, 12 with polymyositis, and 3 with inclusion body myositis) and 30 age-matched controls. We also performed immunocytochemistry for COX II and COX IV subunits in 7 of these patients who had COX deficiency. COX-deficient fibers were a constant finding in patients or controls older than 65 years and the percentage of COX-deficient fibers correlated with age in both patients and controls. Focal COX deficiency was found in 24 patients (13 of 15 with dermatomyositis, 8 of 12 with polymyositis, and 3 of 3 with inclusion body myositis) and 18 controls. The percentages of COX-deficient fibers were higher in patients with inflammatory myopathies (range: 0-4.7%; mean: 1.2%) than in age-matched controls (range: 0-1.9%; mean: 0.4%) (P < 0.01). In the subgroup of patients under age 65, COX-deficient fibers were more frequent in dermatomyositis than in polymyositis (mean: 0.8% vs 0.2%, P = 0.02). In patients with dermatomyositis, capillary loss correlated positively with COX deficiency (P < 0.02). Immunocytochemistry for COX II and IV showed that 82% of COX-negative fibers were COX II-negative and 26% were COX IV-negative, suggesting that proteins encoded by mitochondrial DNA are predominantly, but not exclusively, involved in COX deficiency. We conclude that mitochondrial dysfunction and COX deficiency can occur in inflammatory myopathies. Such a mitochondrial dysfunction is not solely related to the aging process. We suggest that muscle ischemia contributes to mitochondrial dysfunction in dermatomyositis.

Cytochrome c oxidase deficiency in zidovudine myopathy affects perifascicular muscle fibres and arterial smooth muscle cells.

In order to assess the pathogenesis of myopathological alterations induced by zidovudine, we studied muscle samples from 21 patients infected by human immunodeficiency virus with zidovudine myopathy. Cytochrome c oxidase histoenzymatic reaction was evaluated in skeletal muscle fibres and arterial smooth muscle cells. Other investigations included immunocytochemistry for membrane attack complex and endomysial capillary counts. All patients had partial cytochrome c oxidase deficiency. A perifascicular distribution of cytochrome c oxidase-deficient fibres was found in 14 of 21 patients. Cytochrome c oxidase-deficient fibres were significantly more frequent in perifascicular areas than in the complete muscle sections (28% vs 12%, P < 0.001). Cytochrome c oxidase-deficient arteries were found in 11 patients, of whom 10 also had a perifascicular deficiency. Mononuclear microvascular inflammation was observed in four patients and membrane attack complex deposition in capillary walls in two patients. The capillary counts were not significantly different in the patients and in the controls. These results suggest that, in addition to a direct action of zidovudine on mitochondrial DNA, chronic muscle ischaemia related to zidovudine-induced vascular dysfunction might be implicated at the inception of muscle damage in zidovudine myopathy.

[Pharmacokinetics and biotransformation of 3-cyan-2-morpholino-5-(pyrid-4-yl)pyridine (AWD 122-14) in the rat]. / Pharmakokinetik und Biotransformation von 3-Cyan-2-morpholino-5-(pyrid-4-yl)pyridin (AWD 122-14) an der Ratte.

A sensitive isocratic HPLC method for the analysis of AWD 122-14 (1) in plasma and urine was developed. The extraction was processed on-line on a short column. The pharmacokinetics of 1 was studied in rats. The plasma concentration-time course was described by an 1-compartment-model. The pharmacokinetic parameters were estimated. The absorption and elimination of 1 are relatively fast. A single oral dose (D = 1 x 10(-5) mol/kg) was rapidly absorbed (absorption rate constant: kI = 6.85 h-1). The elimination rate constant is kE = 1.59 h-1. The absolute bioavailability of a single oral dose equals 11%. In rats 1 is mainly metabolized. Less than 5% of the dose is excreted in the urine as unchanged drug. The chemical structures of 10 of the 12 isolated metabolites were determined using high-resolution mass spectrometry.

[Potential cardiotonics. 13. Crystal structure, charge distribution and molecular electrostatic potential of 3-cyano-2-(3-diethyl-aminopropylamino)-5-(4-pyridinyl)pyridine (AWD 122-60)]. / Potentielle Kardiotonika. 13. Mitteilung: Kristallstruktur, Ladungsverteilung und molekulares elektrostatisches Potential von 3-Cyan-2-(3-diethylamino-propylamino)-5-(pyrid-4-yl)pyridin (AWD 122-60).

The crystal and molecular structure of the potential cardiotonic agent AWD 122-60 have been determined by X-ray structure analysis. Based on the molecular structure charge distribution and molecular electrostatic potential were evaluated. The results are discussed in comparison with those of other cardiotonic 3,4'-bipyridines.

Influence of platelet activating factor antagonists on the protamine sulphate stimulated release of histamine from peritoneal mast cells of rats in vitro.

The phospholipase (PL)A2 inhibitor p-bromophenacyl bromide (p-BPB), the antagonists of the platelet activating factor (PAF) 3-(4-(2-chlorophenyl)-9-methyl-6H-thieno(3,2-f)-(1,2,4)triazolo(4, 3-a)(1,4)diazepine-2-yl)-1-(4-morpholinyl)-1-propanone (a thieno-triazolo-diazepine, WEB 2086) and terpene-ginkgolide B and the antihistamine with PAF antagonistic qualities 4,9-dihydro-4-(1-methyl-4-piperidinylidene)-10H-benzo[2,5]cyclo hep ta[1,2-b]thiophen-10-one (ketotifen) inhibit in the order p-BPB greater than terpene-ginkgolide B greater than ketotifen greater than WEB 2086 with decreasing activity the protamine sulphate activated histamine release from peritoneal rat mast cells (pRMC) in vitro. All compounds also inhibit the PAF induced aggregation of human platelets. The order of inhibition of the histamine release by these compounds does not agree with the order of their inhibitory activity on PAF induced aggregation of human platelets, indicating that the inhibition of the mast cell degranulation caused by PAF antagonists does not occur via PAF receptors. A generally membrane stabilizing quality of terpene-ginkgolide B and WEB 2086 may be ruled out as the cause of degranulation inhibition because none of the compounds suppresses the cytotoxic, triton X-100 induced release of histamine from pRMC. The mechanism of mast cell degranulation inhibition by PAF antagonists is unclear. An inhibition of PLA2 and/or inhibition of the Ca(2+)-activation are suggested.

[Potential cardiotonic agents. 4. Synthesis, cardiovascular activity, molecular and crystal structure of 5-phenyl- and 4-(4-pyridinyl)-substituted 2(1H)-pyridinethiones]. / Potentielle Kardiotonika. 4. Mitteilung5: Darstellung, kardiovaskuläre Wirksamkeit, Molekül- und Kristallstruktur von 5-phenyl- und 5-(pyrid-4-yl)-substituierten 1,2-Dihydro-pyrid-2-thionen.

Cyclisation of the vinylogous amidinium salt 1 or the 4-ethoxy- and 4-morpholino-3-butene-2-ones, respectively, 4 and 6 with cyano-thioacetamide yielded the 5-(4-pyridinyl)-, 6-methyl-5-(4-pyridinyl)- and 6-methyl-5-phenyl-, respectively, substituted 3-cyano-2(1H)-pyridinethiones 3, 5 and 7. The 2(1H)-pyridinethiones 3, 5 and 7a as well as the in 3-position unsubstituted or carbamoyl substituted derivatives 8 and 9 were obtained from the corresponding 2-chloro-pyridines and potassium sulfide, too. Especially compound 5 showed remarkable positive inotropic potency and, additionally, vasodilator activity. The molecular and crystal structure of 5 have been determines by X-ray structure analysis. Based on the molecular structure charge distribution and electrostatic potential were evaluated. The results are discussed in comparison with those of milrinone.

[Synthesis and analgesic effect of 2-aryliminomethylquinolines]. / Synthese und analgetische Wirkung von 2-Aryliminomethylchinolinen.

2-Aryliminomethylquinolines were synthesized by the condensation of quinoline-2-carbaldehyde with the corresponding anilines. The compounds were evaluated for analgesic activity using the acetic acid writhing test. Some of them showed significant inhibition of the writhing syndrome. The most potent compound 3b was approximately as active as aminophenazone in the writhing and the hot-plate method.

[Quantum chemical studies on substituted benzamidines as inhibitors of the serine proteinases trypsin and thrombin]. / Quantenchemische Untersuchungen an substituierten Benzamidinen als Inhibitoren der Serinproteinasen Trypsin und Thrombin.

Substituted benzamidines are competitive inhibitors of trypsin and thrombin. The aim of this work is to find an interpretation for the relation between chemical structure of the inhibitors and the activity on the both enzymes by quantum chemical methods. For the description of the electrostatic interaction between inhibitor and enzyme the molecular electrostatic potential (MEP) was used. The interpretation took place with the help of a simple model of reactive groups in the enzyme. The obtained results were discussed and compared with those resulting from CNDO/2--reactivity indices. The application of the MEP shows its advantage to investigations of enzyme-inhibitor interactions.

[Hansch analysis of the inhibitory action of 3- and 4-substituted benzamidines on thrombin, plasmin and trypsin (author's transl)]. / Hansch-Analyse der Hemwirkung von 3- und 4-substituierten Benzamidinen gegenüber Thrombin, Plasmin und Trypsin.

Using Hansch formalism, the suthors studied quantitatively the relationship between the structure and the inhibitory action of 3- and 4-substituted amidinophenyl derivatives on thrombin, plasmin and trypsin. It was found that the inhibitory action on all three enzymes depends in the same way from the hydrophobic and electronic properties of the substituents and from an additional term in case of substituents with X-CO-Y structure. The predictive value of the equations is satisfactory.

[Free-Wilson analysis of the inhibitory effect of 4-substituted benzamidines on thrombin, plasmin and trypsin (author's transl)]. / Free-Wilson-Analyse der Hemmwirkung von 4-substituierten Benzamidinen gegenüber Thrombin, Plasmin und Trypsin.

Using the Fujita-Ban model, the authors studied the quantitative structure-inhibitory activity relationships of a series of 4-amidinophenyl compounds with regard to thrombin, plasmin and trypsin. A satisfactory specification of the inhibitory activities was obtained from activity increments of molecular segments.

[Antiviral thiosemicarbazone and related compounds. III. Quantitative relationships between structure and antiviral activity of isantin-beta-isothio-semicarbazone against mengo virus]. / Antivirale Thiosemikarbazone und verwandte Verbindungen III. Quantitative Beziehungen zwischen Struktur und antiviraler Aktivatät von Isatin-beta-isothiosemikarbazonen gegen Mengovirus

The virostatic activity of isatin-beta-isothiosemicarbazones can be described quantitatively by hydrophobic, electronic, and steric substituent constants using multivariate regression analysis. A preceding Free-Wilson analysis allows data smoothening, and thus improved adaptation. Predictions made on the basis of the quantitative structure-action relationships obtained could be confirmed experimentally by synthesizing and testing the corresponding compounds.