Effect of mibefradil on CYP3A4 in vivo

Mibefradil, a calcium channel blocker, was removed from the market because of adverse drug interactions with coadministered CYP3A4 substrates. This study examined the effect of mibefradil on the activity of hepatic and intestinal CYP3A4 in vivo, employing the erythromycin breath test (EBT) and oral midazolam pharmacokinetics. This was a two-period, single-blind, placebo-controlled crossover study in which 8 male volunteers were randomized to the order of receiving placebo and a single 100-mg oral dose of mibefradil. Oral midazolam was coadministered with intravenous [14C N-methyl] erythromycin 1 hour after mibefradil/placebo administration. The EBT was performed 20 minutes following erythromycin administration. Blood and urine were collected during the 36 hours following probe drug administration for analysis of midazolam pharmacokinetics. Coadministration of mibefradil increased the Cmax of midazolam 3-fold, the AUC 8- to 9-fold, and the t1/2 4-fold. Mibefradil coadministration decreased the amount of exhaled 14CO2 in 6 of 8 subjects, with a mean decrease of 25%. It was concluded that a single oral dose of mibefradil significantly inhibits CYP3A4 in intestine and liver. These data support that adverse drug interactions involving mibefradil reflect inhibition of CYP3A4 in intestine and liver. Also, they suggest that the EBT, while a valid probe of in vivo hepatic CYP3A4 activity, is a single time point measurement and may be less sensitive than oral midazolam pharmacokinetics in detecting CYP3A4 inhibition.     

Exposure-dependent inhibition of intestinal and hepatic CYP3A4 in vivo by grapefruit juice

Consumption of typical quantities of grapefruit juice (GFJ) increases the oral bioavailability of several CYP3A4 substrates without affecting their elimination, consistent with selective inhibition of intestinal but not hepatic CYP3A4. However, increases in the AUCs of CYP3A4 substrates recently associated with the consumption of large amounts of GFJ were similar to those observed with potent inhibitors of hepatic CYP3A4. The current study compared the effects of consuming large quantities and more typical amounts of GFJ on the activity of hepatic and intestinal cytochrome P450 3A4 in vivo, employing the erythromycin breath test (EBT) and oral midazolam pharmacokinetics. This was a two-phase, randomized, placebo-controlled crossover study, with each phase conducted with a separate panel of subjects. In Phase I, 8 male volunteers were randomized to the order of receiving one glass (240 mL) of water (placebo) or double-strength (DS) GFJ tid for 2 days and then 90, 60, and 30 minutes prior to administration of probe drugs on the 3rd day. In Phase II, 16 male volunteers were randomized to the order of receiving one glass of (1) single-strength (SS) GFJ, (2) DS GFJ, and (3) water (placebo). All treatments were administered in a fasted state. There was at least a 7-day washout period between treatments. Probe drugs, administered 30 minutes or 1 hour following each treatment in Phase I or II, respectively, consisted of oral midazolam (2 mg) coadministered with IV [14G N-methyl] erythromycin (0.03 mg). The EBT was performed 20 minutes following erythromycin administration. Blood was collected during the 24 hours following probe drug administration for the analysis of midazolam pharmacokinetics. In Phase I, consumption of one glass of DS GFJ tid for 3 days increased the Cmax of midazolam 3-fold, the AUC 6-fold, and the t1/2 2-fold and decreased the amount of exhaled 14CO2 in all 8 subjects, with a mean decrease in EBT of 18%. In Phase II, consumption of one glass of DS GFJ significantly increased the AUC and Cmax of midazolam approximately 2-fold without a significant effect on the t1/2 of midazolam or the EBT. The effects of consuming one glass of SS GFJ on midazolam pharmacokinetics and the EBT were not significantly different from those of one glass of DS GFJ. It was concluded that consumption of one glass of DS GFJ tid for 3 days significantly increased the AUC, Cmax, and t1/2 of midazolam and reduced EBT values, reflecting inhibition of both hepatic and intestinal CYP3A4. In contrast, consumption of one glass of SS or DS GFJ increased midazolam AUC and Cmax, with little effect on the midazolam t1/2 and EBT values, reflecting preferential inhibition of intestinal CYP3A4. Alterations of midazolam AUC and Cmax induced by nine glasses of DS GFJ were significantly greater than those produced by one glass of SS or DS GFJ. These data suggest that GFJ inhibits intestinal and hepatic CYP3A4 in an exposure-dependent fashion and that patients taking medications that are CYP3A4 substrates are at risk for developing drug-related adverse events if they consume large amounts of grapefruit juice.     

Historical evolution of the concept of posttraumatic stress disorder

The authors elaborate on the historical evolution of the concept of Posttraumatic Stress Disorder (PTSD). The authors quote the French scholars, mainly Charcot and Janet, as the first to connect traumatic events and symptoms of hysteria. The contributions of Freud are described with enphasis on his effort into integrating the intra-psychic and environmental dimensions. Kardiner is referred as the author who coined the concept of 'war neurosis', which was deemed as an important one during the Second World War and Vietnam War. In conclusion, the authors highlight that the concept of PTSD used in the Diagnostic and Statistical Manual of Mental Disorders (DSM) by the American Psychiatric Association assess, at the same time, how treatening was the traumatic event and the list of symptoms presented by the patients.     

The influence of health care organisations on health system performance

OBJECTIVES: The governments of many countries are undertaking initiatives to assess the extent to which health care organisations fulfil important objectives of health care, such as health improvement, fair access and efficiency. However, the extent to which these health care organisations can influence these objectives is unclear. The purpose of this study is to examine the potential influence of English National Health Service territorial health authorities on 14 indicators of system performance. METHODS: The study uses performance data relating to approximately 5000 small geographical areas with average populations of 10,000. Multi-level statistical models are used to attribute variation in the indicators to three hierarchical levels--small areas, district health authorities and regional health authorities--after controlling for socio-demographic characteristics. Variations in indicators attributable to district or regional level give an indication of the extent to which health authorities may influence performance. RESULTS: After adjusting for socio-demographic characteristics, the proportion of variation in performance attributable to district health authorities varies from about 8% (for standardised mortality ratios) to about 76% (for waiting time for elective surgery). Variation at the regional level is smaller than at the district level. CONCLUSIONS: There appear to be very large variations between indicators in the extent to which health care organisations can influence health system performance. Choice of performance indicators and the managerial incentive regime based on the indicators should recognise this variability, as it is highly dysfunctional to hold managers accountable for measures of performance that are beyond their control.     

Epithelioid sarcoma of the penis--a rare differential diagnosis of Peyronie's disease

We report on a case of penile epithelioid sarcoma in a 29-year-old man presenting with a dorsal penile plaque that primarily was misdiagnosed as Peyronie's disease. Although the initial clinical findings of these two different entities appear similar, the consequence for the patient is severe. The only way of differentiating these disorders are histological findings. The principal microscopic characteristics of epithelioid sarcoma are the distinctive nodular arrangement, central degeneration and necrosis of the tumor cells with epithelioid appearance and eosinophilia. Immunohistochemical data (cytokeratin, epithelial membrane antigen, vimentin, CD 34, desmin) confirm the diagnosis. We conclude that in cases with slightest doubts on the diagnosis of Peyronie's disease, especially in younger men suffering from a fast-growing penile induration, a bioptic clarification of the entity should be performed to exclude a high malignant disease that can be only treated as far as it is localized by radical surgery.     

Sample sizes for batch acceptance from single- and multistage designs using two-sided normal tolerance intervals with specified content

One quality control test in the pharmaceutical industry is a test for uniformity of content of a batch prior to release of the batch to market. For batch acceptance by this or other quantitative tests of batch quality, one approach uses two-sided tolerance intervals of specified content. If the tolerance interval falls entirely within an acceptance interval, the batch is accepted. This has the form of a statistical hypothesis test. Once we recognize this approach as a statistical test, we can ask what sample size is required to be able to accept the batch with a desired power. The power for a single-stage design is a bivariate noncentral t probability and can be determined using previously published algorithms. Using standard methods for interim analyses, the approach is extended to multistage designs. Power and sample size for multistage designs are validated with simulations. We demonstrate it is possible to design one- and two-stage designs for batch acceptance with desired power and specified type I level.     

Limits of 80%-125% for AUC and 70%-143% for Cmax. What is the impact on bioequivalence studies?

OBJECTIVE: The US Food and Drug Administration (FDA) currently uses bioequivalence (BE) limits for fasting BE studies that are based on the 90% confidence interval for the ratio of difference of the test and reference products Cmax and AUC falling within 80% to 125%. The FDA has also proposed that BE limits be used similarly for AUC and Cmax measurements from fed BE studies. In some cases, regulatory agencies have considered a wider BE limit for Cmax, because of the typically higher variability of Cmax compared to AUC. We investigated the consequences of changing from an 80%/ 125% limit for both pharmacokinetic measures to one that uses a limit of 80%/125% for AUC and 70%/143% for Cmax. METHODS: We computed the sample sizes required for BE studies using 80%/125% for AUC and 70%/143% for Cmax as BE limits. We also determined the range of the ratios of Cmax and AUC values in a study that could meet the 70%/143% and 80%/125% BE limits. RESULTS: The sample size for the study, in order to have adequate power with 80%/125% for AUC and 70%/143% for Cmax, will be determined primarily by the intrasubject variability of AUC, though with a substantial proportion of studies (about one third) still determined by the variability of Cmax. The ratio of mean Cmax values that can pass a wider 70%/143% BE limit could easily be as high as 128%. CONCLUSION: Without further scientific or clinical rationale, we find it difficult to justify widening the bioequivalence limit for Cmax to 70%/143% for either fasting or fed BE studies.