Prediction of the effect of erythromycin, diltiazem, and their metabolites, alone and in combination, on CYP3A4 inhibition

Predictive models of complex drug-drug interactions between multiple inhibitors and their metabolites have not been evaluated. The purpose of this study was to evaluate an interaction model for cytochrome P450 3A4 (CYP3A4) that incorporated the simultaneous reversible and irreversible inhibition by multiple inhibitors. Erythromycin (ERY) and diltiazem (DTZ), and their major metabolites, N-desmethylerythromycin (nd-ERY) and N-desmethyldiltiazem (nd-DTZ), were chosen to evaluate the model. k(inact) (rate constant for maximal inactivation), K(I) (inhibitor concentration at 50% maximal inactivation), and K(i) (reversible inhibition constant) were estimated for ERY, DTZ, nd-ERY, and nd-DTZ, respectively, using cDNA-expressed CYP3A4 and human liver microsomes under optimal experimental conditions. To evaluate the interaction model, combinations of inhibitors and metabolites were incubated at concentrations equal to K(I), (1/2)K(I), and 2K(I) of each inhibitor for specified durations in both enzyme systems. The models were further evaluated by the incubation of combinations of inhibitors with the substrate testosterone for 10 min. CYP3A4 inhibition in the presence of drug mixtures was predicted from the inhibition parameters determined for each drug or metabolite alone. The CYP3A4 activity in the presence of multiple inhibitors was well predicted by the model incorporating additive irreversible inhibition as modified by mutual competitive inhibition (percent mean error and percent mean absolute error ranged from -0.06 to 0.04 and from 0.03 to 0.09, respectively). In conclusion, the additive model predicted the combined effect of multiple inhibitors on CYP3A inhibition in vitro. However, simultaneous reversible and irreversible inhibition effects should be taken into account in a reaction mixture of substrate and multiple inhibitors of CYP3A4.     

Ultrastrukturelle Veränderungen am Nierenparenchym durch ESWL unter Acetylsalicylsäure (ASS)

BACKGROUND: The risk of hemorrhagic complications after extracorporeal shock-wave lithotripsy (ESWL) increases in patients with aspirin intake, but the hematoma-inducing mechanism has not been understood completely at the ultrastructural level. METHODS: The effect off shock-waves on the kidneys of male Wistar-rats (n=24) was investigated in an experimental setting using a special ESWL device. Ultrastructural examination was performed by light-, transmission electron- and scanning electron microscopy. RESULTS: Shock-wave induced tissue damage appeared in all kidneys independently of aspirin intake. Endothelial detachment, lethal cell injury, gaps and mechanical disruption of the glomerular basement membrane were regularly found. After 1 week, repair processes were completed with evidence of permanent fibrosis in some cases. CONCLUSIONS: ESWL can induce modest as well as fatal damage to renal tissue cells. Therefore, after an ESWL-induced hematoma a second ESWL should not be performed within 1 week of the first treatment.     

Lymphangiomyomatosis: CT, chest radiographic, and functional correlations

Eight patients with the diagnosis of lymphangiomyomatosis were evaluated with computed tomography (CT), chest radiography, and pulmonary function tests to determine the relationship between the extent of disease seen on imaging studies and functional status. Chest radiographic assessment included the subjective determination of disease extent and measurements of lung length and the arc of the right hemidiaphragm. Disease extent on CT scans was scored as a percentage of lung that was abnormal on the basis of visual assessment of the degree of cystic replacement of the lung parenchyma. Significant correlations were observed between CT scores and percentages of predicted forced expiratory volume in 1 second/forced vital capacity (r = -.92, P less than .002) and diffusing capacity of the lungs for carbon monoxide (r = -.80, P less than .017). No significant correlations were observed between subjective chest radiographic scores and pulmonary function tests, although measurements of lung length and percentage of predicted total lung capacity were correlated (r = .76, P less than .045). CT was more accurate than chest radiography in defining the presence and extent of parenchymal cysts and provided for greater morphologic-physiologic correlation. CT, particularly high-resolution CT, may be useful in the diagnosis and longitudinal evaluation of patients with this disease and may be more sensitive than pulmonary function tests in the early stages of lung damage.     

Miliary tuberculosis: A complication of intravesical BCG treatment

A case of miliary tuberculosis following intravesical bacillus Calmette-Guerin (BCG) treatment is described.     

Gene Probe Analysis in an Informative Family with Multiple Endocrine Neoplasia Syndrome Type 2A (MEN 2A). Improvement in Carrier Risk Estimation

Gene probe analysis of the MEN 2A locus on chromosome 10 hasbeen undertaken using the markers TB10.163, RBP 3 and TB14.34in a large kindred with familial medullary thyroid carcinomas,with or without phaeochromocytomas or primary hyperparathyroidism.A maximum LOD score of 2.97 gave strong evidence of close linkagewith zero recombination. For 12 members of the family so far not known to be affectedby any form of the disease the estimated risk of carrying thegene has been considerably decreased in all but one, whose riskhas been greatly increased.     

Medical treatment of hepatic amebic abscess: rare need for percutaneous drainage

Although amebic liver abscess can virtually always be successfully treated medically, percutaneous drainage has been advocated recently. In 96 recently treated patients, therapeutic aspiration and percutaneous drainage were rarely needed. Most cases were correctly diagnosed by means of clinical, laboratory, and sonographic findings. Abscesses in only 13 (13.5%) patients were diagnostically aspirated. An abscess in one patient was therapeutically aspirated because the patient was responding slowly to medical therapy. No patient required catheter drainage. The key to successful amebic abscess management is medical therapy. Therapeutic drainage is rarely needed. Successfully treated patients occasionally respond slowly to medical therapy, and successfully treated amebic abscesses may enlarge or become bizarre-appearing on sonograms. This should not prompt therapeutic drainage. Diagnostic aspiration is appropriate when amebic and pyogenic abscesses are indistinguishable using clinical and imaging findings. Rare indications for therapeutic aspiration or drainage include pyogenic superinfection and large, juxtacardiac abscesses (potential intrapericardial rupture).     

Ninety-day toxicity study of sodium monochloroacetate in Sprague-Dawley rats

Male and female Sprague-Dawley rats were administered the sodium salt of monochloroacetic acid (SMCA) by oral gavage for a period of 90 consecutive days. Dosage levels of 15, 30, 60 or 120 mg/kg per day were employed. SMCA clearly induced toxicity in both females and males, with the greatest severity in the male animals. Both the liver and kidneys were identified as target organs. At 120 mg/kg per day, 30% of females and 80% of the males died, most within the first 2 days of treatment. Hemorrhagic and congested lungs (possibly a postmortem change) were seen in the early deaths (1-3 days) whereas liver lesions were observed in later deaths. In addition, there was nephrotoxicity as evidenced by elevated creatinine, blood calcium (BCAL), and blood urea nitrogen (BUN) levels. Hepatotoxicity was indicated by increases in the serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Both organs showed increased organ-to-body weight ratios. Microscopic examination revealed a significant (P less than or equal to 0.001) increase in chronic renal nephropathy and increased splenic pigmentation at 60 mg/kg per day in the males. Based on the observation of toxicity at all treatment levels in males, a lowest observed adverse effect level (LOAEL) of 15 mg/kg per day is proposed for a 90-day exposure to SMCA by oral gavage to the Sprague--Dawley rat.