In vitro study on fluoxetine adsorption onto charcoal using potentiometry.

This in vitro investigation was performed to study the adsorption rate constant as well as the adsorption characteristics of fluoxetine (F) to activated charcoal and its commercial formulation Carbomix powder in simulated gastric (pH 1.2) fluid environment. Ion-selective electrode (ISE) potentiometry, based on the selective, direct and continuous monitoring of F with an F-ISE constructed in our laboratory was used. The method used in the kinetic experiments consists of the rapid addition of a slurry containing the charcoal into the drug solution under stirring and continuous recording of the F-ISE potential until the establishment of equilibrium. The free ionized drug concentration at appropriate time intervals was calculated from the recorded adsorption curve and the apparent adsorption rate constant was estimated assuming pseudo first order kinetics. Within run R.S.D. of the estimates ranged from 0.24 to 11.5%, while between run R.S.D. (n=3-4) ranged from 0.90 to 13.8%. A linear relationship was found between the apparent adsorption rate constants and the amount of charcoal used with slopes (+/-S.D.) for activated charcoal and Carbomix equal to 1.14(+/-0.21) and 0.146(+/-0.009) s(-1)g(-1), respectively. Successive additions of microvolumes of F solution were made into a charcoal slurry with measurement of the F-ISE potential at equilibrium. The maximum adsorption capacity values (+/-S.D.) of activated charcoal and Carbomix were 254.8+/-1.8 and 405+/-41 mg/g, respectively while the affinity constant values (+/-S.D.) were 45.6+/-2.2 and 55.5+/-2.9 l/g, respectively. The adsorption of F to charcoals was rapid and for amounts of charcoal 10 times greater than the amount of the drug, 95% of F was adsorbed within the first 5 min. Relative to the toxic and lethal doses in cases of F intoxications, both types of charcoals tested adsorbed effectively F at gastric pH. Carbomix can be considered as appropriate charcoal formulation for medical treatment in cases of F poisoning.     

Multimodal approaches to high-risk prostate cancer

Widespread use of testing for prostate-specific antigen (PSA) has led to a migration in the stage and grade of prostate cancer (PCa), with most men presenting with localized disease. However, 20%-35% of patients still present with high-risk disease (PSA > 20 ng/mL, biopsy Gleason score 8-10, or clinical stage T3). Despite advances in various treatment modalities, patients with high-risk disease have a significant chance of recurrence and death after surgery, often because of the presence of early occult metastasis at time of diagnosis. The optimal management of high-risk pca remains controversial. The present article aims to discuss the traditional approaches and the more recent evolution toward multimodal therapies.     

Investigation of the retention/pH profile of zwitterionic fluoroquinolones in reversed-phase and ion-interaction high performance liquid chromatography

The retention/pH profiles of three fluoroquinolones, ofloxacin, norfloxacin and ciprofloxacin, was investigated by means of reversed-phase high performance liquid chromatography (RP-HPLC) and reversed-phase ion-interaction chromatography (RP-IIC), using an octadecylsilane stationary phase and acetonitrile as organic modifier. Sodium hexanesulphonate and tetrabutylammonium hydroxide were used as sources of counter ions in ion-interaction chromatography. The retention/pH profiles under in RP-HPLC were compared to the corresponding lipophilicity/pH profiles. Despite the rather hydrophilic nature of the three fluoroquinolones positive retention factors were obtained while there was a shift of the retention maximum towards more acidic pH values. This behavior was attributed mainly to non-hydrophobic silanophilic interactions with the silanized silica gel material of the stationary phase. In ion-interaction chromatography the effect of counter ions over a broad pH range was found to be ruled rather by the ion pair formation in the mobile phase which led to a drastic decrease in retention as a consequence of the disruption of the zwitterionic structure and thereupon the deliberation of a net charge in the molecules. At pH values at which zwitterionic structure was not favored both the ion-exchange and ion pair formation mechanisms were assumed to contribute to the retention.     

Simultaneous HPLC determination of ketoprofen and its degradation products in the presence of preservatives in pharmaceuticals

A novel and quick high-performance liquid chromatography (HPLC) method with UV spectrophotometric detection was developed and validated for the determination of five compounds in topical gel. The described method is suitable for simultaneous determination of active component ketoprofen, two preservatives methylparaben and propylparaben and two degradation products of ketoprofen--3-acetylbenzophenone and 2-(3-carboxyphenyl) propionic acid--in a topical cream after long-term stability tests using ethylparaben as an internal standard. The chromatographic separation was performed on a 5microm Supelco Discovery C18 column (125mm x 4mm i.d., Sigma-Aldrich); the optimal mobile phase for separation of ketoprofen, methylparaben, propylparaben, degradation products 3-acetylbenzophenone and 2-(3-carboxyphenyl) propionic acid and ethylparaben as internal standard consists of a mixture of acetonitril, water and phosphate buffer pH 3.5 (40:58:2, v/v/v). At a flow rate of 1.0ml min(-1) and detection at 233nm, the total time of analysis was less than 10min. The method was applied for routine analysis (batch analysis and stability tests) of these compounds in topical pharmaceutical product.     

Automated stopped-flow analyser in clinical chemistry: determination of albumin with bromcresol green and purple

We describe an adaptation of a microcomputer-controlled stopped-flow analyzer for automated analysis of albumin in serum. The immediate reaction between bromcresol green or purple and albumin is used to develop a routine procedure with 12 s reaction time. The approach shows excellent linearity to 68 g/l, good sensitivity, a relative SD of less than 0.5%, mean recovery 99.1%, high sample throughput (180 prediluted samples/h) and no significant interferences. The 'reaction time' related overestimation of albumin that appears in prolonged procedures is eliminated, and results with this method correlate well with those obtained using the more specific immunonephelometric method.     

A displacement approach for competitive drug-protein binding studies using the potentiometric 1-anilino-8-naphthalene-sulfonate probe technique.

A displacement approach for competitive binding studies was developed. The method utilizes the potentiometric 1-anilino-8-naphthalene-sulfonate (ANS) probe technique and is applied to the binding study of several non-steroidal anti-inflammatory drugs (NSADs) to bovine serum albumin (BSA). A home-made ANS electrode was used to monitor the displaced free ANS probe from its binding sites on the protein molecule by the stepwise addition of the studied drug. To assess and compare quantitatively the displacing ability of the various drugs, the 'ANS Displacement Index' is used. The possible interference of 19 ionizable drugs (NSADs, sulfonamides, etc.) to the ANS selective electrode at pH 7.4 was studied and their potentiometric selectivity coefficients (K(pot)(ANS,D)) were determined. Correction procedures for the determination of the free ANS concentration are proposed in the case of interfering ionic drugs. A blank binding experiment in conjunction with the incorporation of K(pot)(ANS,D) values in the 'general competitive site oriented model' allows one to derive estimates for the drug binding parameters, i.e. the number of binding sites and association constants.     

Radical prostatectomy for high-risk clinically localized prostate cancer: a prospective single institution series

Objective:

The objective of this paper is to report on the pathologic and biochemical progression-free outcomes of patients who underwent radical prostatectomy for high-risk localized prostate cancer.

Methods:

Data was collected prospectively from 299 patients who underwent radical prostatectomy for high-risk clinically localized prostate cancer by 2 surgeons at a single institution. High risk was defined as 1 or more of 3 adverse factors: prostate-specific antigen (PSA) >20, biopsy Gleason score 8 to 10 and clinical stage T3. PSA recurrence was defined as PSA >0.4 ng/mL or any salvage therapy.

Results:

Median age was 63.3 years (46.1–75.9). Median follow-up was 4.7 years (range 0.5–17.3 years). PSA at diagnosis was >20 ng/mL in 31.4%. Biopsy Gleason score was 8 to 10 in 66.9%. Clinical stage was T3 in 24.4%. 81.6% of patients had a single baseline risk factor, 15.7% had 2 risk factors and 2.7% had all 3 risk factors. Neoadjuvant therapy was administered to 184 patients (61.5%). Pathologic stage was organ-confined in 39.6%, specimen-confined in 26%, non-specimen-confined in 26.4%, and 8% had lymph node positive disease. Overall survival, cancer-specific survival and biochemical progression-free survival was 99%, 99.67% and 70.2%, respectively. Univariate analysis showed that PSA at diagnosis, percentage of cores positive and number of risk factors were predictors of PSA recurrence (p < 0.05). Multivariate analysis showed that PSA at diagnosis was an independent predictor of PSA recurrence (p < 0.05).

Conclusion:

Radical prostatectomy is associated with favourable biochemical progression-free, clinical and overall survival in selected men with high-risk localized prostate cancer, and should therefore be considered an option in these patients. Baseline PSA >20 ng/mL is a significant independent predictor of PSA recurrence.     

In-vitro study on the competitive binding of diflunisal and uraemic toxins to serum albumin and human plasma using a potentiometric ion-probe technique

The competitive binding of diflunisal and three well-known uraemic toxins (3-indoxyl sulfate, indole-3-acetic acid and hippuric acid) to bovine serum albumin (BSA), human serum albumin (HSA) and human plasma was studied by direct potentiometry. The method used the potentiometric drug ion-probe technique with a home-made ion sensor (electrode) selective to the drug anion. The site-oriented Scatchard model was used to describe the binding of diflunisal to BSA, HSA and human plasma, while the general competitive binding model was used to calculate the binding parameters of the three uraemic toxins to BSA. Diflunisal binding parameters, number of binding sites, n(i) and association constants for each class of binding site, K(i), were calculated in the absence and presence of uraemic toxins. Although diflunisal exhibits high binding affinity for site I of HSA and the three uraemic toxins bind primarily to site II, strong interaction was observed between the drug and the three toxins, which were found to affect the binding of diflunisal on its primary class of binding sites on both BSA and HSA molecules and on human plasma. These results are strong evidence that the decreased binding of diflunisal that occurs in uraemic plasma may not be solely attributed to the lower albumin concentration observed in many patients with renal failure. The uraemic toxins that accumulate in uraemic plasma may displace the drug from its specific binding sites on plasma proteins, resulting in increased free drug plasma concentration in uraemic patients.