Stability Study of Parenteral N-Acetylcysteine, and Chemical Inhibition of Its Dimerization.

Parenteral N-acetylcysteine has a wide variety of clinical applications, but its use can be limited by a poor chemical stability. We managed to control parenteral N-acetylcysteine stability, and to study the influence of additives on the decrease of N-acetylcysteine degradation. First, an HPLC-UV dosing method of N-acetylcysteine and its main degradation product, a dimer, was validated and the stability without additive was studied. Then, the influence of several additives (ascorbic acid, sodium edetate, tocopherol and zinc) and of temperature on N-acetylcysteine dimerization was evaluated. Finally, the influence of zinc gluconate at different concentrations (administrable to patients) was investigated. Zinc gluconate at 62.5 µg·mL-1 allows the stabilization of 25 mg·mL-1 N-acetylcysteine solution for at least 8 days when stored at 5 ± 3 °C.

Severe decrease of cyclosporine levels in a heart transplant recipient receiving the direct thrombin inhibitor argatroban.

This case report is about a suspected interaction between argatroban, a direct thrombin inhibitor, and cyclosporine, which occurred in a 60-year-old patient after a second heart transplantation. We explored 4 possible mechanisms of interaction, which are an analytical interference, an idiopathic hemodilution, an increase of renal and hepatic clearance, and a metabolic drug-drug interaction.

Effect of fluid loading during hypovolaemic shock on caspofungin pharmacokinetic parameters in pig.

INTRODUCTION: Caspofungin treatment is frequently initiated in shock patients. In the present study, we investigated the influence of hypovolaemic shock requiring fluid loading on the plasma and pulmonary pharmacokinetic parameters of caspofungin in the pig. METHODS: After being anaesthetised and mechanically ventilated, 12 pigs were bled to induce a two-hour deep shock and resuscitated using normal saline based on haemodynamic goals. A one-hour infusion of 70 mg of caspofungin was started at the beginning of the resuscitation period. The lungs were removed four hours after caspofungin administration. Sixteen animals served as controls without haemorrhage. Caspofungin concentrations were measured by using high-performance liquid chromatography, and a two-compartment population pharmacokinetic analysis was performed. RESULTS: In the shock group, the volume of blood removed was 39 ± 7 mL/kg and a volume of 90 ± 17 mL/kg saline was infused throughout the resuscitation period. The extravascular lung water index was higher in the shock group (9.3 ± 1.6 mL/kg vs 5.7 ± 1 mL/kg in the control group; P < 0.01). In the shock group, the median (interquartile range) maximal plasma concentration was 37% lower than in the control group (21.6 µg/mL (20.7 to 22.3) vs 33.1 µg/mL (28.1 to 38.3); P < 0.01). The median area under curve (AUC) from zero to four hours was 25% lower in the shock group than in the control group (60.3 hours × µg/mL (58.4 to 66.4) vs 80.8 hours × µg/mL (78.3 to 96.9); P < 0.01), as was the median lung caspofungin concentration (1.22 µg/g (0.89 to 1.46) vs 1.64 µg/g (1.22 to 2.01); P < 0.01). However, the plasma-to-tissue ratios were not different between the groups, indicating that lung diffusion of caspofungin was not affected after shock followed by fluid loading. Pharmacokinetic analysis showed that the peripheral volume of distribution of caspofungin and intercompartmental clearance were significantly higher in the shock group, as was the total apparent volume of distribution. CONCLUSIONS: Hypovolaemic shock followed by fluid loading in the pig results in a significant increase in the apparent volume of distribution of caspofungin and in a decrease in its plasma and pulmonary exposition. Although our model was associated with capillary leakage and pulmonary oedema, our results should be generalised to the septic shock with caution. Future investigations should focus on monitoring plasma caspofungin concentrations and optimal caspofungin dosing in shock patients.

Tacrolimus/mycophenolate mofetil improved natural killer lymphocyte reconstitution one year after kidney transplant by reference to cyclosporine/azathioprine.

BACKGROUND: Recently introduced immunosuppressive drugs are more potent to control graft rejection, but current concerns are raised regarding their potential to increase long-term neoplastic and infectious complications. Considering the role of B, T, or natural killer (NK) lymphocyte in controlling alloreactive, anti-infectious, and antitumoral immune responses, we compared the impact of two immunosuppressive regimens on lymphocyte subsets one year following kidney transplant. METHODS: Multivariate regression analysis of variables affecting lymphocyte subset counts was retrospectively performed on 91 kidney-transplanted patients, analyzed before graft, at day 15 and 1-year postgraft. These patients were included in a randomized prospective open trial comparing tacrolimus/mycophenolate mofetil (FK/MMF) versus cyclosporine/azathioprine (CSA/Aza), both used in association with rabbit antithymocyte globulines (rATG) induction and prednisone. RESULTS: Fifteen days postgraft, severe T and NK lymphocyte depletion were observed in all patients, while B cell counts were selectively higher in the FK/MMF group as compared to before graft. One-year posttransplant, NK cell counts and NK cell cytotoxicity was significantly higher in patients receiving FK/MMF therapy, as compared to CSA/Aza. Cytomegalovirus (CMV) infection during the first year posttransplant was also associated to higher NK, CD8, and CD4CD8 T cell counts at month 12. CONCLUSIONS: In addition to its higher potential in preventing graft rejection, we show that after one year of transplant, FK/MMF better preserves NK innate immune effector cells and their cytotoxic potential. These data prompt to further evaluate the role of NK cells in relation to antiviral and tumoral surveillance of transplanted patients, which are common complications of long-term immunosuppression.

Identification by single-strand conformational polymorphism analysis of known and new mutations of the CYP3A5 gene in a French population.

The cytochrome P450 3A5 (CYP3A5) has been shown to be highly involved in the metabolism of many therapeutic agents. To date, several polymorphisms affecting the CYP3A5 gene have been identified but few studies have shown a complete description of the variability of the CYP3A5 in the French population. Therefore, the extent of CYP3A5 genetic polymorphism was investigated in a French population of 114 patients. The screening of the coding region with their intron-exon boundaries and the proximal flanking regions was performed using a PCR-SSCP strategy. Eighteen polymorphisms were identified, including four new mutations. They correspond to -19 T>C upstream of the exon 1, 7360 T>C in intron 4, 12991 T>C in intron 5 and 29788 delG in exon 12. We also identified 13 alleles including six new alleles. As expected, the most frequent allelic variant is CYP3A5*3, with a frequency of 87% of all alleles. These data confirmed that CYP3A5 gene is highly polymorphic. Furthermore, it will be now interesting to evaluate the impact of this polymorphism on the pharmacokinetic parameters of different drugs.

Effects of sufentanil or ketamine administered in target-controlled infusion on the cerebral hemodynamics of severely brain-injured patients.

OBJECTIVE: The manual injection of a bolus of opioid in patients with brain injury induces an increase in intracranial pressure related to a decrease in mean arterial pressure. Such an effect has not been observed with the use of ketamine. The use of target-controlled infusion would minimize or suppress this adverse effect of opioid. This study evaluated the effects of an increase in plasma concentrations of sufentanil or ketamine administered by target-controlled infusion on cerebral hemodynamics. DESIGN: Prospective, randomized study. SETTING: Intensive care unit in a trauma center. PATIENTS: Thirty patients with severe traumatic brain injury. INTERVENTIONS: Patients were assigned to receive sedation consisting of sufentanil-midazolam or ketamine-midazolam using target-controlled infusion. Twenty-four hours after the onset of sedation, the target concentrations of sufentanil or ketamine were doubled for 15 mins. Blood samples were collected to determine the actual plasma concentration of sufentanil and ketamine, before and 15 mins after concentration change. MEASUREMENTS AND MAIN RESULTS: The baseline values of intracranial pressure and cerebral perfusion pressure were similar in both groups. The two-fold increase in drug concentrations did not involve a significant change for intracranial pressure, cerebral perfusion pressure, and mean velocity of middle cerebral artery in both the ketamine and the sufentanil groups. The measured plasma concentrations of sufentanil and ketamine were 0.4 +/- 0.2 ng/mL and 2.6 +/- 2.2 mug/mL, respectively, before the increase in concentrations and 0.7 +/- 0.4 ng/mL and 5.5 +/- 3.8 mug/mL after. CONCLUSIONS: The present study shows that the increase in sufentanil or ketamine plasma concentrations using a target-controlled infusion is not associated with adverse effects on cerebral hemodynamics in patients with severe brain injury. The use of target-controlled infusion could be of interest in the management of severely brain-injured patients. However, there is a need for specific pharmacokinetic models designed for intensive care unit patients.

Moxifloxacin penetration in bronchial secretions of mechanically ventilated patients with pneumonia.

The pharmacokinetics of moxifloxacin was studied in 17 mechanically ventilated patients with pneumonia. Patients were given 400 mg of moxifloxacin intravenously. Blood samples and bronchial secretions were taken on days 1 and 4. A dose of 400 mg of moxifloxacin allows one to achieve efficient concentrations in bronchial secretions and plasma.

Brain tissue penetration of ciprofloxacin following a single intravenous dose.

Ciprofloxacin distribution was assessed in cerebral tissues in 14 patients undergoing craniotomy. The study objective was to determine the brain tissue/serum concentration ratio of ciprofloxacin. Patients received a single intravenous (iv) 200 mg dose of ciprofloxacin. Mean (+/- S.D.) tissue/serum concentration ratios were (mg/kg): parietal fat during opening 1.40 +/- 1.05, during closure 1.34 +/- 1.17, in the dura mater 2.26 +/- 1.36, in skull bone during opening 0.44 +/- 0.29, during closure 0.97 +/- 1.57 and in brain tissue 0.88 +/- 0.99. Mean (+/- S.D.) concentrations of ciprofloxacin in brain tissue were 0.87 +/- 0.08 mg/kg, suggesting that a dose >200 mg iv ciprofloxacin is required to ensure therapeutic concentrations in brain tissue.