Erica Hoffer

N-acetylcysteine increases the glutathione content and protects rat alveolar type II cells against paraquat-induced cytotoxicity

A protective effect of N-acetylcysteine in oxidative lung damage was reported by a number of workers; however, the mechanism underlying this effect was not thoroughly elucidated. The present research investigates the protection by N-acetylcysteine against paraquat-induced cytotoxicity to alveolar type II cells, which are known to be specific targets of paraquat toxicity in vivo. We found that addition of 1 mM N-acetylcysteine to alveolar type II cells incubated with 1 mM paraquat reduced the cytotoxic index from 17.4 +/- 1.3% to 9.3 +/- 1.5%. This effect could not be explained by the interference of N-acetylcysteine with the active uptake of paraquat by type II cells. Incubation of these cells with N-acetylcysteine enhances their glutathione content, thus reducing the paraquat- induced depletion of glutathione in these cells. These results suggest that N-acetylcysteine exerts its protective effect by acting as a precursor for glutathione in alveolar type II cells.

Busulfan Use in Hematopoietic Stem Cell Transplantation: Pharmacology, Dose Adjustment, Safety and Efficacy in Adults and Children

Busulphan (1, 4-bis [methanesulfonyl-y] butane) is a bi-functional alkylating agent that, in combination with cyclophosphamide, has been commonly used in conditioning regimens before hematological stem cell transplantation (HSCT) for nearly 20 years. Busulfan has a very narrow therapeutic index, and acute toxicity may be related to absorption and disposition of the drug and metabolites. Precise delivery of the oral formulation is compromised by erratic gastrointestinal absorption, particularly in infants and small children. An intravenous busulfan formula was approved nearly 40 years after the approval of the oral formulation. Busulfan levels expressed as the area under the concentration-time curve (AUC) higher than 1500 microM* minute were reported to increase the risk of developing veno-occlusive disease (VOD), while low levels may result in engraftment failure or disease relapse. VOD occurs in 11-40% of patients undergoing HSCT and is associated with death in 3.3% of patients. Measurement of individual plasma busulfan levels during oral or intravenous dosing to obtain an AUC is likely to provide the necessary elements to monitor the drug disposition, ensuring efficacy and preventing toxicity of patients undergoing HSCT. It is also important to consider the busulfan drug-drug interactions and adverse drug reactions that can develop during the therapeutic process. Busulfan therapeutic drug monitoring and dose-adjustment should be performed in specialized laboratories staffed by well-trained personnel.

Use of Saliva in Home Monitoring of Carbamazepine Levels

Summary: Total carbamazepine (CBZ) levels in serum of 61 epileptic children were compared with saliva levels. Both resting and stimulated saliva was analyzed. The salivary levels were 38.6% of serum CBZ levels. A highly significant correlation was noted (r= 0.89, p < 0.001). Stimulation had no effect on saliva CBZ levels (r= 0.97). Salivary and serum CBZ levels were not affected by storing the samples for 7 days at room temperature. The data indicate that salivary CBZ may provide a reliable alter‐native monitoring method to Tegretol therapy, especially in children, in whom blood sampling is difficult. Further‐more, the samples may be collected at home and delivered to the laboratory by mail.

Determination of Urinary Hippuric Acid in Toluene Abuse

Background: Volatile substance abuse is practiced mainly by adolescents and young adults. Its effects are central nervous system excitation followed by central nervous system depression, at times accompanied by seizures. It may cause sudden death as a result of ventricular arrhythmias, reflex vagal inhibition, respiratory depression, and anoxia. Chronic toxicity may involve the nervous system, heart, kidney, and liver. Toluene-based adhesives are among the most commonly inhaled substances. Case Report: A 14-year-old female presented with confusion, hallucinations, and intermittent laughing and crying after having inhaled contact glue several times daily in the course of 5 days. Her condition improved within 3 h. Urinary hippuric acid was 93.9 g/g creatinine indicating heavy toluene exposure (biological exposure index, BEI, is 1.6 g/g creatinine). Conclusion: In this patient, urinary hippuric acid was a biomarker for her toluene abuse.

N-Acetylcysteine enhances the action of anti-inflammatory drugs as suppressors of prostaglandin production in monocytes.

The anti-inflammatory effect of non-steroidal anti-inflammatory drugs (NSAIDs) is associated with inhibition of cyclooxygenase (COX), the rate-limiting enzyme responsible for the synthesis of prostaglandins. Since oxygen free radicals can act as second cellular messengers, especially to modulate the metabolism of arachidonic acid and the prostaglandin tract, it seems plausible that antioxidants might affect the production of prostaglandin by activated cells. This research is focused on the effect of the antioxidant N-acetylcysteine (NAC) on the inhibition of prostaglandin E(2) formation in activated monocytes by specific and non-specific COX inhibitors. We found that lipopolysaccharide-induced prostaglandin E(2) formation was significantly reduced by rofecoxib and by diclofenac, two NSAIDs. Addition of NAC to each of these drugs enhanced the effect of the NSAIDs. These results suggest that one might expect either a potentiation of the anti-inflammatory effect of COX inhibitors by their simultaneous administration with NAC, or obtaining the same anti-inflammatory at lower drug levels.

Evaluation of a Liposome System for the Delivery of Desferrioxamine to Lungs in Rats

Abstract— Liposomes with various lipid composition and sizes, prepared by two different techniques were evaluated for their potential to deliver desferrioxamine to lungs as a treatment against oxidative lung damage. Multilamellar vesicles (MLV) and reverse evaporation vesicles were prepared out of a lipid mixture containing dipalmitoyl phosphatidylcholine, stearyl amine, cholesterol and vitamin E. The administration of desferrioxamine‐encapsulated liposomes to rats by the intravenous route at a dose of 100 mg kg−1, significantly prolonged the presence of desferrioxamine in all the tested organs when compared with the administration of free desferrioxamine. The injection of reverse evaporation vesicles extruded through a 2 μm polycarbonate membrane exhibited a longer residence time of the desferrioxamine and of liposomal vitamin E in lungs compared with the other types of liposomes tested. The examination of liposome components in the bronchoalveolar lavage fluid (BALF) and the alveolar macrophages recovered from BALF revealed that about 7 × 10−3% of the administered desferrioxamine dose was recovered by this technique at 3 and 17 h after liposome administration. This high residual concentration in the alveolar space confirms the hypothesis that liposomes can be delivered to the lung tissue when encapsulated in alveolar macrophages.

Comparison of everolimus QMS immunoassay on Architect ci4100 and liquid chromatography/mass spectrometry: lack of agreement in organ-transplanted patients.

Background: Liquid chromatography with mass spectrometry (LC–MS/MS) is the method of choice for the determination of everolimus whole blood concentrations but is not always available. Therefore, immunoassays have been developed for clinical monitoring of everolimus. In previous studies, the Quantitative Microsphere System (QMS) immunoassay had a positive bias compared with LC–MS/MS, but was judged acceptable, although clinical agreement (eg, 95% limits of agreement) was not reported. The objective of this study was to assess whether the agreement between the QMS assay and an LC–MS/MS method was clinically acceptable for use interchangeably in therapeutic everolimus monitoring. Methods: Whole blood samples from organ-transplanted patients on everolimus therapy were analyzed by both QMS (on Architect ci4100 analyzer) and LC–MS/MS. Paired results were compared using paired Student t test, Bland–Altman plots, and Deming regression analysis. The proportions of falsely supratherapeutic and subtherapeutic results on the QMS assay compared with the LC–MS/MS were calculated. Results: Among 250 samples (169 patients), mean everolimus concentrations determined by LC–MS/MS and QMS assays were 4.8 ± 2.1 ng/mL and 6.3 ± 2.1 ng/mL, respectively (P < 0.001), with 95% lines of agreement between −2.1 and 5.2 ng/mL, a range corresponding to 152% of the mean concentration. When stratified by the type of transplant, a similar positive bias was found in each subgroup (all P < 0.014). Sixty-nine percent of the samples yielding supratherapeutic concentrations (>8 ng/mL) on the QMS assay were within the therapeutic range on the LC–MS/MS. Conclusions: The everolimus QMS immunoassay, using the Architect ci4100 analyzer, had a significant positive bias compared with LC–MS/MS, with a wide range between the limits of agreement. The lack of agreement may result in inadequate everolimus dose adjustments, suggesting that the QMS assay cannot be used interchangeably with the LC–MS/MS method for therapeutic everolimus monitoring in organ-transplanted patients.

A simple approximation for Busulfan dose adjustment in adult patients undergoing bone marrow transplantation

Busulfan is an alkylating agent used in preparative regimens before bone marrow transplantation (BMT). Busulfan concentrations in plasma, expressed as the area under the concentration–time curve (AUC), were reported to correlate with treatment outcome. Because busulfan is administered in 16 doses of 1 mg/kg every 6 hours for 4 days, the opportunities to “correct” the dose as a consequence of the measured AUC are limited to the 16-dosage protocol. In the present research busulfan pharmacokinetics were prospectively evaluated in 27 adult patients treated according to the above protocol by measuring the first, second, and fifth dose AUC. The pharmacokinetic analysis was based on a noncompartment model for extravascular absorption, but calculations according to a 1-compartment model gave similar results. A simple mathematical approximation allowed prediction of the AUC of the second dose from that of the first and the busulfan concentration at trough. Fifteen patients had the dose adjusted at the fourth dose to obtain an AUC within the “therapeutic window” of 950–1500 μM-min. This procedure was then validated by the measurement of the fifth dose AUC. It appears that this simple pocket calculator method allows a rapid evaluation of the need and the extent of dose adjustment and proved to be a valuable tool to improve busulfan administration in pre BMT treatment.

Percutaneous Permeability to Paraqut: In Vitro Experiments with Human Skin

AbstractPercutaneous permeability to paraquat through intact and mechanically damaged human skin was measured in vitro from diluted solutions (1 mg/ ml). In intact human skin under occlusion, a permeability to paraquat of 3 × 10−5 cdhr was measured at steady state. The binding of paraquat to skin was determined and found to be negligible. The measured permeabilities were used in a pharmacokinetic model to predict paraquat levels in blood and lungs. The model predicts that for intact human skin and diluted paraquat solutions systemic toxicity is unlikely. However, the risk increased significantly when damaged skin or concentration paraquat solutions are involved.

Monitoring of busulfan area under the curve : Estimation by a single measurement

Because the busulfan area under the concentration–time curve (AUC) has been correlated with the outcome of bone marrow transplantation (BMT) and the occurrence of veno-occlusive disease after BMT, a rapid determination of AUC is needed to ensure its suitable dosage. The present work describes a method based on combining aliquots from the 10 blood samples collected for an AUC busulfan determination and performing a single determination of the resulting mixture. In 42 patients undergoing a preparative regimen for bone marrow transplantation this combined sample AUC was compared with the regular determined AUC obtained from 10 consecutive samples drawn at various time intervals after dosing. It is apparent that the AUCs calculated by pharmacokinetic analysis using a noncompartmental model package and those obtained by analyzing the sample mixture are very similar (r = 0.961). The proposed method allows rapid adjustment of the busulfan dose, reducing the number of uncorrected dosages during therapy.