Determination of travoprost and travoprost free acid in human plasma by electrospray HPLC/MS/MS

A quantitative method for the analysis of AL-5848, the (+)-enantiomer of fluprostenol (FP), in human plasma is described. Plasma was spiked with a tetradeuterated analog of travoprost free acid (AL-5848X) as internal standard (IS) and acidified with 0.1 M formic acid. Sample clean up was performed using reversed phase solid-phase extraction. Following elution of the compounds of interest and evaporation to dryness, the residue was reconstituted in methanol:water (1:1) and chromatographed on an octadecylsilica (C18) column with negative ion electrospray ionization tandem mass spectrometry. The [M[bond]H](-) ions at m/z 457 and 461 for the analyte and IS, respectively, were subjected to collisional fragmentation with argon to yield the same intense 3-trifluoromethylphenolate (m/z 161) product ion. The validated concentration range was 0.010-3.00 ng/ml based on a 1.0 ml plasma aliquot. Fully adequate accuracy, precision, specificity, recovery and stability for routine use in clinical pharmacokinetic studies were demonstrated. Analysis of a second plasma aliquot following incubation with rabbit esterase allows the isopropyl ester pro-drug, travoprost (AL-6221), to be determined by difference.     

Comparing bimatoprost and travoprost in black Americans

ABSTRACT

Objective: To compare the intraocular pressurelowering efficacy and safety of topical bimatoprost 0.03% with that of travoprost 0.004% for the reatment of black patients with open-angle glaucoma (OAG) and ocular hypertension (OHT).

Research design and methods: Multicenter, prospective, randomized, investigator-masked trial of 94 black patients previously diagnosed with OAG or OHT. All patients completed washout of ocular hypotensive medications before study participation. Patients were assigned to either once-daily bimatoprost 0.03% or once-daily travoprost 0.004% for 3 months.

Main outcome measures: The primary outcome measures were mean intraocular pressure (IOP), mean change from baseline IOP, and percentage of patients who reached a target IOP reduction. Secondary measures included ophthalmologic examination and adverse events.

Results: Both bimatoprost and travoprost significantly lowered IOP at all study visits (?p < 0.001). Bimatoprost provided mean IOP reductions from baseline that ranged from 6.8?mmHg to 7.8?mmHg (27% to 31%). Travoprost provided mean IOP reductions from baseline that ranged from 6.2?mmHg to 6.9?mmHg (25% to 28%). By month 3, 85% of participants in the bimatoprost group had a mean IOP reduction of at least 20%, compared with 68% of those in the travoprost group. Furthermore, 31.9% of those in the bimatoprost group had a mean IOP reduction of more than 40% at month 3 compared with 20.9% of those in the travoprost group. There were no significant differences in biomicroscopy, ophthalmoscopy, or visual acuity. Ocular redness was the most commonly reported adverse event in both treatment groups. No serious adverse events were reported.

Conclusions: Bimatoprost and travoprost each effectively lowered IOP in this population of black patients. More patients achieved clinically relevant IOP reductions with bimatoprost.     

Precautions in the use of Michaelis-Menten kinetics in the prediction of phenytoin levels

The Michaelis-Menten equation is one of the various techniques available for predicting steady-state plasma levels of phenytoin. In actual practice, however, data are not always available or reliable. This case report emphasizes the importance of establishing the quality of the data and determining that steady state has been achieved. The addition of a third point to the graph used to estimate parameters greatly increases prediction accuracy.     

Precautions for routine use of INT-reductase activity for measuring biological activities in soil and sediments

To evaluate toxicity of xenobiotics on microflora of soils and sediments, reduction of tetrazolium dye [2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazolium chloride (INT) or 2,3,5 triphenyltetrazolium chloride (TTC)] by dehydrogenase activities is commonly used, but many questions are posed about the biological relevance of this test. In this work, INT was chosen to evaluate the influence of some experimental factors on reductase activity. INT adsorption to soil, concentration of INT, and sterilization methods were tested on different soils and sediments to determine bioavailability of INT, saturation concentration, and intensity of chemical reduction. INT adsorption shown dramatic variations vs type of soil, from 0 to 100%, and was particularly linked with cation exchange capacity. Formaldehyde seems to be the best method with irradiation to determine abiotic reduction, particularly with sediments. However, it must be stressed that the tetrazolium reduction in microbial systems can be carried out by other enzymatic systems than malate dehydrogenase. INT is an excellent substrate of membrane hydrogenases found in numerous anaerobic bacteria. This was observed with experiments conducted with Rhodobacter capsulatus in our laboratory. © by John Wiley & Sons, Inc.     

The use of mechanistic data and the handling of scientific uncertainty in carcinogen risk assessments. The trichloroethylene example

The purpose of this paper is to explore how risk assessors actually use mechanistic data in carcinogen risk assessment and to discuss how the handling of scientific uncertainty may affect the outcome of the risk assessment. The analysis is performed by comparing 29 trichloroethylene risk assessment documents in general and 2 of these, namely the ECETOC (1994, Trichloroethylene: Assessment of Human Carcinogenic Hazard, Technical Report No. 60) and the OECD/EU (1996, Initial Assessment Report for the 4th SIAM (Screening Information Data Set Initial Assessment Meeting), May 1996: Trichloroethylene, sponsor country, United Kingdom [Draft]), in more detail. It is concluded that in this example the ECETOC required less evidence for considering a carcinogenic mechanism irrelevant to humans than did the OECD/EU risk assessors. There are examples of when two risk assessors have selected different primary data for their argumentation and also examples of how one and the same primary publication was interpreted differently. Biased data selection and evaluation of primary data that correlate to the risk assessor's overall conclusions have also been identified. The general comparison of all 29 TCE risk assessment documents indicates that the assessment of scientific uncertainty in the mechanistic data affects the overall conclusions.     

Optimised sample handling in association with use of the CMA 600 analyser

A large degree of variability for batched analysis of serially collected microdialysis samples measured with the CMA 600 analyser has been described. This study was designed to identify sources of variability related to sample handling. Standard concentrations of four solutes were placed in microdialysis vials and then stored and analysed at intervals. Results were analysed for variability related to vial and cap type, duration and temperature of storage, centrifugation and re-analysis. The main results were that centrifugation of samples reduced variability. When a batch of 24 samples was analysed, the use of crimp caps reduced evaporation. Samples in glass vials with crimp caps could be stored in a refrigerator for up to 14 days without large variability in concentration compared to plastic vials which demonstrated variability already when stored for more than 1 day. We conclude that variability in microdialysis results can occur in relation to storage and analysis routines if routines are not optimised concerning evaporation. Centrifugation before analyses, glass vials with crimp caps even during frozen storage, and attention to minimal times for samples to be uncapped during analysis all contribute to minimise variability in the handling and analysis of microdialysis samples.     

Renal handling of iodobenzoates in rats.

Renal elimination pathways of three positional isomers of iodobenzoic acid (2-iodobenzoate, 3-iodobenzoate and 4-iodobenzoate radiolabelled with 125I) were compared using the perfused rat kidney in-situ. All agents were eliminated both in a parent form (involving all renal elimination mechanisms i.e. glomerular filtration, tubular secretion, and tubular reabsorption) and also metabolized to a large extent in the kidney. After 3-iodobenzoate and 4-iodobenzoate administration, the major fractions of radioactivity found in urine were in the form of their metabolites, whereas 2-iodobenzoate was eliminated into urine mostly as the parent compound. Proportions of the individual metabolites in the urine of the perfused rat kidney were similar to those in intact rats for all agents. The results suggest that the kidney is the major organ for both the excretion and metabolism of iodobenzoates in rats. The principal renal metabolic reaction for all compounds under study was conjugation with glycine to produce the corresponding hippuric acid derivatives.     

How to use medical and drug information: view of integrated information handling

It has become very easy to import drugs from overseas due to the spread of the Internet, and this has made the construction of a country-wide system that ensures safety a complicated matter. Although drug information and side-effect information databases are widely used, what is the situation concerning non-medicinal health foods that find their way into Japan from overseas? If the harmful effects of unknown substances can be prevented, it will be very beneficial. I would like to discuss these problems from the point of view of handling medical information.     

Renal handling of biphosphonate alendronate in rats.

Alendronate is a bisphosphonate that is secreted via a saturable pathway in rat kidney. This study is designed to discover if the rate-determining step in its net renal secretion is uptake into the renal tubule. The tissue uptake clearance of alendronate by the kidney, estimated from an integration plot analysis and normalized with respect to plasma protein binding, was 4.2 times higher at a tracer dose than that of inulin, indicating uptake of alendronate by the renal tubules. The uptake clearance is comparable with the net secretion clearance obtained from an infusion study, indicating that the rate-determining step in the net secretion is uptake under the tracer conditions. When the dose was increased, however, there was no reduction in uptake clearance while the net secretion clearance fell to almost zero. The urinary excretion clearance defined with respect to the steady state concentration in the kidney also fell to almost zero. This result suggests that saturation of the net secretion of alendronate is caused by saturation of membrane transport through the brush-border membrane. Thus, it would seem that there is a transport mechanism for alendronate on the brush-border membrane of kidney epithelial cells.     

Pharmacokinetics and renal handling of enprofylline in pregnant rats.

The pharmacokinetics and renal handling of enprofylline during pregnancy were investigated in Sprague-Dawley rats. Significant differences in the pharmacokinetic parameters of enprofylline were observed between nonpregnant rats and pregnant rats on the 20th day of gestation: volume of distribution was higher, and systemic clearance was lower in pregnant rats. Parameters obtained from rats at 7 days postpartum were the same as those obtained from nonpregnant rats. There were no significant differences in the fraction of urinary excretion of enprofylline between nonpregnant and pregnant rats. The protein binding of enprofylline in the plasma of pregnant rats was significantly lower than in nonpregnant rats, as a decrease in the albumin concentration consequentially reduced the binding capacity of enprofylline. The volume of distribution for unbound enprofylline in pregnant rats was not significantly different from nonpregnant rats, although a significant decrease was observed in pregnant rats in the systemic clearance for unbound enprofylline. In addition, the clearance ratio was lower in pregnant rats (2.8) when compared with nonpregnant rats (6.4). Pregnancy caused a decrease in the apparent maximum capacity of transport (Vmax) from 29.9 to 20.8 micrograms/min and in the Michaelis-Menten constant (KM) from 2.59 to 2.26 micrograms/ml, indicating that the tubular secretion ability of enprofylline becomes reduced during pregnancy. These results suggest that changes that occur in the plasma protein binding behavior and in renal handling as a result of pregnancy are primary factors influencing the disposition of enprofylline during pregnancy.     

Ocular hypotensive efficacy of travoprost in patients unsuccessfully treated with latanoprost

SUMMARY

Objective: To evaluate the efficacy of travoprost 0.004% monotherapy in patients unsuccessfully treated with latanoprost monotherapy.

Research design and methods: Open-label, non-comparative study conducted at US academic and private practice clinics in adult patients with ocular hypertension or primary open-angle glaucoma who required a change in therapy (due to either inadequate efficacy or safety issues) as judged by the investigator. Intraocular pressure (IOP) was measured at entry and 30?days later.

Main outcome measures: Mean change in intra-ocular pressure (mm Hg).

Results: Reported here are 488 per-protocol patients from 330 centers who were using latanoprost monotherapy prior to study entry, and who received travoprost monotherapy during the study. Patients had a mean age of 69?years, were approximately two-thirds Caucasian, 60% female, predominantly brown or blue eyes, and 91% were diagnosed as having primary open-angle glaucoma. The mean days in treatment were 31.9 ± 6.4. Mean IOP at study entry was 21.2?mm Hg. Following travoprost monotherapy, this was reduced by a mean of 3.2?mm Hg to 18?mm Hg (?p < 0.0001, paired t-test). There were 21 adverse events reported in the intent-to-treat (ITT) population for an incidence of 3.5%. There were some limitations to the current study including: no washout period, no control therapy, single IOP determinations at the beginning and the end of the study; patient compliance with the initial therapy was not measured, and the study was not masked. This study reflects a real-life situation of what a clinician can expect when he changes a patient from latanoprost monotherapy to travoprost monotherapy.

Conclusion: This study showed that travoprost provided a statistically and clinically significant reduction (?p < 0.0001) in IOP of 3.2?mm Hg for patients who had not been successfully treated with latanoprost monotherapy. The results of this trial demonstrate the potential benefit of using travoprost as a replacement therapy in order to ensure adequate IOP control.     

Ocular hypotensive efficacy of travoprost in patients unsuccessfully treated with latanoprost

OBJECTIVE: To evaluate the efficacy of travoprost 0.004% monotherapy in patients unsuccessfully treated with latanoprost monotherapy. RESEARCH DESIGN AND METHODS: Open-label, noncomparative study conducted at US academic and private practice clinics in adult patients with ocular hypertension or primary open-angle glaucoma who required a change in therapy (due to either inadequate efficacy or safety issues) as judged by the investigator. Intraocular pressure (IOP) was measured at entry and 30 days later. MAIN OUTCOME MEASURES: Mean change in intraocular pressure (mm Hg). RESULTS: Reported here are 488 per-protocol patients from 330 centers who were using latanoprost monotherapy prior to study entry, and who received travoprost monotherapy during the study. Patients had a mean age of 69 years, were approximately two-thirds Caucasian, 60% female, predominantly brown or blue eyes, and 91% were diagnosed as having primary open-angle glaucoma. The mean days in treatment were 31.9 +/- 6.4. Mean IOP at study entry was 21.2 mm Hg. Following travoprost monotherapy, this was reduced by a mean of 3.2 mm Hg to 18 mm Hg (p < 0.0001, paired t-test). There were 21 adverse events reported in the intent-to-treat (ITT) population for an incidence of 3.5%. There were some limitations to the current study including: no washout period, no control therapy, single IOP determinations at the beginning and the end of the study; patient compliance with the initial therapy was not measured, and the study was not masked. This study reflects a real-life situation of what a clinician can expect when he changes a patient from latanoprost monotherapy to travoprost monotherapy. CONCLUSION: This study showed that travoprost provided a statistically and clinically significant reduction (p < 0.0001) in IOP of 3.2 mm Hg for patients who had not been successfully treated with latanoprost monotherapy. The results of this trial demonstrate the potential benefit of using travoprost as a replacement therapy in order to ensure adequate IOP control.     

The toxicity and renal handling of paraquat in cynomolgus monkeys.

The acute intravenous and oral toxicity of single doses of paraquat dichloride was studied in the cynomolgus monkey. Renal handling and effects upon renal function were also investigated following an oral dose of [14C]paraquat. Clinical signs consisted of vomiting, anorexia and dyspnoea. By 48 h all animals showed signs of acute renal failure with oliguria, high plasma urea and SGPT levels and metabolic acidosis. Animals dosed orally showed similar, though less severe, signs to those dosed intravenously. The oral LD50 was approx. 70 mg paraquat cation/kg. Following an oral dose plasma levels peaked by 2 h, but were constant from 12 h to 24 h. Paraquat clearance was high initially and exceeded the creatinine and urea clearance, but fell off markedly after 14 h as renal failure developed. By 18 h urine production had ceased. It is concluded that acute renal failure and acute pulmonary damage are the main causes of death, with interstitial pulmonary fibrosis being a factor in animals surviving the acute phase.