Nitrosoureas lomustine, carmustine and fotemustine induced hepatotoxic perturbations in rats: biochemical, morphological and flow cytometry studies.

Chloroethylnitrosoureas are reactive compounds that are highly effective against malignant neoplasms in humans and animals. The most widely used nitrosoureas, lomustine and carmustine, are known to be hepatotoxic and to induce pericholangitis and intrahepatic cholestasis, which in the long term lead to cholangiolysis and biliary cirrhosis. However, the nitrosourea fotemustine has proved to be non-hepatotoxic at 20 mg/kg and 50 mg/kg. We have studied the effect of these three nitrosoureas on the cytotoxicity and cellular kinetics of rat liver cells. Lomustine and carmustine modify the proliferation index of liver cells in vivo: flow cytofluorometry showed that DNA cell distribution is quite similar for lomustine and carmustine, with subsequent accumulation of cells in G2 + M phase. 3 months later regressive morphological and cell cycle perturbations are noted for the lower dose of lomustine and carmustine. The most severe lesions are noted with lomustine (50 mg/kg). Fotemustine is not hepatotoxic and preferentially induces S phase perturbations. The more toxic nitrosoureas, lomustine and carmustine, induce comparable hepatocyte cell cycle alterations which differ from those induced by the less hepatotoxic nitrosourea fotemustine.

Efficacy and safety of rilmenidine for arterial hypertension.

To assess the long-term acceptability and efficacy of rilmenidine (S 3341), patients with placebo-resistant hypertension (diastolic blood pressure [BP] greater than or equal to 95 mm Hg and less than 115 mm Hg) were included in an open 1-year treatment study. Eight examinations allowed treatment adaptation if diastolic BP remained greater than or equal to 90 mm Hg (monotherapy with rilmenidine, 1 or 2 mg/day, followed by the addition of a diuretic, then tritherapy). Three hundred seventeen patients, aged 58.0 +/- 0.7 years, were included. Two hundred sixty-nine were followed for 1 year and 48 withdrew from the trial without any symptom suggesting a withdrawal syndrome: 4 because of adverse effects; 6, lack of efficacy despite triple therapy; 9, intercurrent diseases; 10, noncompliance independent of adverse effects; 18, personal reasons not associated with treatment; and 1, lost to follow-up. On the 12th month, the decrease in supine systolic and diastolic BP reached 25 and 17 mm Hg with monotherapy (n = 150), 26 and 17 mm Hg with double therapy (n = 90) and 20 and 15 mm Hg with triple therapy (n = 29). BP was normalized (diastolic BP less than or equal to 90 mm Hg) on months 6 and 12 in 80 and 84% of the patients, respectively. Monotherapy was maintained in 66 and 60% of these patients, respectively, two-thirds being treated with 1 mg once daily. Adverse effects with monotherapy were mainly observed at the beginning of treatment in 3 to 8%: dry mouth, asthenia, gastralgia, palpitations, drowsiness, insomnia; other adverse effects were rare (1 to 2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Early monitoring of human renal transplantations by N-acetyl-beta-D-glucosaminidase isoenzyme activities in urines.

Monitoring of variations in N-acetyl-beta-D-glucosaminidase (NAG) urinary activity, following renal transplantation, has been proposed for the early diagnosis of rejection episodes. In this study, the measurement of urinary NAG-B activity was conducted as a complement to total NAG (A + B) measurement, which is normally used alone. Selective measurement of NAG-B activity is carried out after fixation of NAG-A on ion exchanger in test tubes. Results of NAG (A + B) activity confirm that the assay of urinary NAG is a useful indicator of rejection, but a positive correlation between NAG-B and NAG (A + B) activities was observed during the various complications which can occur after transplantation. The specific measurement of this isoenzyme does not, therefore, seem to provide additional information in the early monitoring of human renal transplantations. Apart from rejection episodes, other factors are likely to produce marked NAG-B excretion, e.g. gentamicin therapy.

Cytotoxicity and DNA damaging effects of a new nitrosourea, fotemustine, diethyl- 1-(3-(2-chloroethyl)-3-nitrosoureido) ethylphosphonate-S10036.

Fotemustine is a new chloroethylnitrosourea which has recently entered a Phase II clinical trial. Using standard cytotoxicity analyses, Fotemustine was shown to be preferentially active in two Mer- cell lines, human colon BE and human lung A427. Comparative cell kill in the Mer+ counterparts HT29 and A549 (respectively) was significantly lower. In a mouse cell line, P388, alkaline elution studies showed that Fotemustine caused fewer DNA strand breaks and total crosslinks (including DNA-protein) than either BCNU or MeCCNU at equivalent cytotoxic concentrations. In addition, the removal of DNA damage caused by Fotemustine was more rapid than of damage, three times as much Fotemustine was required. These data suggest that the cytotoxic mechanism of Fotemustine, although subject to the same repair mechanisms as other nitrosoureas, may not be entirely dependent upon DNA as the sole drug target. The previously reported reduced mutagenicity of this agent may also be a function of the less extensive nucleic acid damage. The encouraging early clinical trial results with this drug may reflect its improved pharmacokinetics and bioavailability, rather than any significant modification in its cellular pharmacology when compared to other nitrosoureas.

Complete bioavailability and lack of food-effect on pharmacokinetics of gliclazide 30 mg modified release in healthy volunteers.

A new modified release (MR) formulation containing 30 mg of gliclazide was developed to obtain a better predictable release of the active principle and to allow once-daily dosing regimen. An absolute bioavailability study was carried out to characterise the performance of the new formulation and the food-effect was also investigated in a separate study. Both studies were single dose, randomised, open label, two way cross over studies with a wash out period between doses. For the bioavailability study, each volunteer received 30 mg of gliclazide given either as a 1 h intravenous infusion or as a 30 mg MR tablet. For the food-effect study, the treatment was given either fasted or 10 min after the start of a standardised Melander breakfast. Blood samples were collected up to 72 h after administrations and plasma samples assayed for gliclazide concentrations using a reverse-phase HPLC method with UV detection. Mean absolute bioavailability of gliclazide was 97% and ranged between 79 and 110% showing complete absorption. A similar moderate to low variability was observed after IV and oral administration showing the MR formulation did not add to the overall variability which is solely due to the disposition parameters, in particular metabolism of gliclazide. No significant difference was observed in t(max), t(1/2z), C(max) and AUC of gliclazide after administration of the 30 mg MR tablet under fasted and fed conditions. In conclusion, after single oral administration of a 30 mg MR tablet, gliclazide was completely absorbed both under fasted and fed conditions. A consistent and optimal release of gliclazide from this formulation leads to a low to moderate overall variability of its pharmacokinetic parameters. Diamicron 30 mg MR can be given without regards to meals i.e. before, during or after breakfast.

Population PKPD modelling of the long-term hypoglycaemic effect of gliclazide given as a once-a-day modified release (MR) formulation.

AIMS: To study the relationship between the pharmacokinetics (PK) of gliclazide and its long-term pharmacodynamic (PD) effect in a large population of Type 2 diabetic patients and to identify factors predicting intersubject variability. METHODS: A PKPD database of 634 Type 2 diabetic patients with a total of 5,258 fasting plasma glucose (FPG) samples was built up from the data collected during the clinical development of a modified release formulation of gliclazide (gliclazide MR). The PKPD analysis used a nonlinear mixed effect modelling approach. A mixture model was used to identify patients with a FPG response to treatment. In patients identified as responders, the decrease in FPG was related to gliclazide exposure (AUC) by an Emax relationship. An effect compartment was used to describe the link between PK and PD. A linear disease-progression model was used to assess the glycaemic deterioration observable over several months of treatment. Simulations were performed to evaluate the predictive performance of the PKPD model and to illustrate the time course of the antidiabetic effect of gliclazide MR. RESULTS: Disease state was found to be the main explanatory factor for intersubject variability in response to gliclazide. The percentage of responders to gliclazide, used as monotherapy, increased inversely to the number of classes of antidiabetic agents received prior to entry in the studies. In responders, the initial dose (30 mg) of the gliclazide MR dosing regimen induced half of the maximum hypoglycaemic effect. The equilibration half-life between the PK and PD steady states was 3 weeks (intersubject variability of 84%). The rate of disease progression was 0.84 mmol l(-1) year(-1) (intersubject variability 143%). The PKPD model adequately predicted the FPG profiles of 234 patients who received the current formulation of gliclazide. Simulation of a 1-year parallel dose ranging clinical trial illustrated the influence of dose, time and type of previous antidiabetic treatment on the percentage of patients with clinically significant improvement of blood glucose control. CONCLUSIONS: This population PKPD analysis has characterized the relationship between the exposure to gliclazide and its long-term hypoglycaemic effect, and has established that the intersubject variability in response is mostly related to disease state. These results underline the clinical interest of quickly increasing the dose of gliclazide MR according to the response to treatment in order to achieve effective blood glucose control.

Effects of the new nitrosourea derivative, fotemustine, on the glutathione reductase activity in rat tissues in vivo and in isolated rat hepatocytes.

Fotemustine, a new clinically active nitrosourea, is demonstrated herein to be a poor inhibitor of glutathione reductase activity from rat liver, lung and kidney cytosols. In order to show that an intracellular step of activation does not lead to a toxic intermediary metabolite, rat hepatocytes were incubated with fotemustine. Their glutathione-related pathways were checked and shown not to be altered, while under similar experimental conditions BCNU was shown to be dramatically harmful. Furthermore, association of fotemustine with a H2O2 production leading drug, diquat, was shown to be inefficient--while BCNU is efficient--in potentiating the diquat toxicity. Considering the role of glutathione level in the detoxification of mutagens and carcinogens, the advantage of fotemustine over BCNU in therapeutic use seems substantiated.