Claudia F. Clavijo

Polymer-Free Biolimus A9-Coated Stent Demonstrates More Sustained Intimal Inhibition, Improved Healing, and Reduced Inflammation Compared With a Polymer-Coated Sirolimus-Eluting Cypher Stent in a Porcine Model

Background—Drug-eluting stents effectively reduce restenosis but may increase late thrombosis and delayed restenosis. Persistent polymer, the drug, or a combination of both could be responsible. Local delivery of Biolimus A9, a rapamycin derivative, from a polymer-free BioFreedom stent (Biosensors International) may prevent these complications. Methods and Results—We compared high-dose (HD) (225 &mgr;g/14 mm Biolimus A9) and low-dose (LD) (112 &mgr;g/14 mm Biolimus A9) BioFreedom stents with a polymer-coated sirolimus-eluting Cypher stent (SES) and a bare-metal stent (BMS) at 28 days and 180 days in an overstretch coronary mini-swine model with histomorphometric and histological analysis. At 28 days, there was a reduction in neointimal proliferation by HD, LD, and SES compared with BMS (neointimal thickness: HD, 0.080±0.032; LD, 0.085±0.038; SES, 0.064±0.037; BMS, 0.19±0.111 mm; P<0.001; BMS > HD/LD/SES). At 180 days, both BioFreedom stents were associated with reduced neointimal proliferation, whereas SES exhibited increased neointima (neointimal thickness: HD, 0.12±0.034; LD, 0.10±0.040; SES, 0.20±0.111; BMS, 0.17±0.099 mm; P<0.001; SES > HD/LD; BMS > LD). At 180 days, BioFreedom stents showed decreased fibrin and inflammation, including granuloma and giant cells, compared with SES. Conclusions—The polymer-free Biolimus A9–coated stent demonstrates equivalent early and superior late reduction of intimal proliferation compared with SES in a porcine model. After implantation of BioFreedom stent, delayed arterial healing was minimal, and there was no increased inflammation at 180 days compared with SES implantation. The use of polymer-free stents may have a potential long-term benefit over traditional polymeric-coated drug-eluting stents.

A low blood volume LC‐MS/MS assay for the quantification of fentanyl and its major metabolites norfentanyl and despropionyl fentanyl in children

Preterm and term neonates often require surgical procedures and analgesia. However, our knowledge about neonatal pharmacokinetics of fentanyl, the most commonly used drug for these procedures, and its metabolites is still incomplete. To facilitate pharmacokinetic studies of fentanyl and its metabolites in neonates and other children, we developed and validated an LC-MS/MS method based on minimally invasive, low blood volume sampling. LC-MS/MS was used for the simultaneous analysis of fentanyl, despropionyl fentanyl (DPF), and norfentanyl from dried blood samples (DBS) collected on filter paper. Positive ions were monitored using multiple reaction monitoring. Since the standard matrix for measuring fentanyl blood concentrations is plasma, the assay was developed and validated in plasma, whole blood, and then DBS. Our method was able to measure clinically relevant levels of fentanyl and its metabolites. In DBS, the lower limits of quantification were 100 pg/mL for fentanyl with a range of reliable response from 0.1 to 100 ng/mL (r(2)>0.99) and 250 pg/mL for both DPF and norfentanyl with a range of reliable response from 0.25 to 100 ng/mL (r(2)>0.99). In plasma and in DBS inter-day accuracy and precisions of fentanyl met predefined acceptance criteria and also indicated comparable assay performance in both matrices.

Comparison of the quantification of acetaminophen in plasma, cerebrospinal fluid and dried blood spots using high-performance liquid chromatography–tandem mass spectrometry

Acetaminophen (paracetamol, N-(4-hydroxyphenyl) acetamide) is one of the most commonly prescribed drugs for the management of pain in children. Quantification of acetaminophen in pre-term and term neonates and small children requires the availability of highly sensitive assays in small volume blood samples. We developed and validated an LC-MS/MS assay for the quantification of acetaminophen in human plasma, cerebro-spinal fluid (CSF) and dried blood spots (DBS). Reconstitution in water (DBS only) and addition of a protein precipitation solution containing the deuterated internal standard were the only manual steps. Extracted samples were analyzed on a Kinetex 2.6 μm PFP column using an acetonitrile/formic acid gradient. The analytes were detected in the positive multiple reaction mode. Alternatively, DBS were automatically processed using direct desorption in a sample card and preparation (SCAP) robotic autosampler in combination with online extraction. The range of reliable response in plasma and CSF was 3.05-20,000 ng/ml (r(2)>0.99) and 27.4-20,000 ng/ml (r(2)>0.99) for DBS (manual extraction and automated direct desorption). Inter-day accuracy was always within 85-115% and inter-day precision for plasma, CSF and manually extracted DBS were less than 15%. Deming regression analysis comparing 167 matching pairs of plasma and DBS samples showed a correlation coefficient of 0.98. Bland Altman analysis indicated a 26.6% positive bias in DBS, most likely reflecting the blood: plasma distribution ratio of acetaminophen. DBS are a valid matrix for acetaminophen pharmacokinetic studies.

Development and validation of a semi-automated assay for the highly sensitive quantification of Biolimus A9 in human whole blood using high-performance liquid chromatography-tandem mass spectrometry.

Drug-eluting stents are sustained-release intra-coronary devices that are usually coated with a few hundred micrograms of drug. Measuring the drugs that are released over weeks in order to assess human pharmacokinetics is a challenge that requires assays with high sensitivity. We developed and validated a semi-automated LC-MS/MS assay for the quantification of Biolimus A9, a proliferation signal inhibitor that was specifically developed for coating on drug-eluting stents in human EDTA blood. The only manual step was the addition of a zinc sulfate/methanol protein precipitation solution which included the internal standard. Samples were injected into the HPLC and extracted online. The assay had the following performance characteristics: range of reliable response 0.01-100 ng/mL (r(2)>0.99), inter-day accuracy (0.033 ng/mL): 111.7%, and inter-day precision: 8.6%. There was no ion suppression, matrix interferences or carry-over. Extracted samples were stable in the autosampler at +4 degrees C for at least 24 h and could undergo three freeze-thaw cycles. The assay, with a lower limit of detection of 333 fg/mL and a lower limit of quantitation of 10 pg/mL, was sufficiently sensitive and robust for quantifying Biolimus A9 in clinical trials after i.v. injection and after stent implantation.

Prior epidural lidocaine alters the pharmacokinetics and drug effects of extended-release epidural morphine (DepoDur®) after cesarean delivery.

BACKGROUND: A potential physicochemical interaction between epidural local anesthetics and extended-release epidural morphine (EREM) could negate the sustained release. In this study, we sought to determine the pharmacokinetic and drug effects of prior epidural lidocaine administration on EREM. METHODS: Thirty healthy women undergoing cesarean delivery were enrolled in this randomized study. Patients received 8 mg EREM 1 hour after either a combined spinal-epidural (intrathecal bupivacaine and fentanyl 20 &mgr;g with no epidural medication; group SE) or an epidural anesthetic (epidural 2% lidocaine with fentanyl 100 &mgr;g; group E). Maximal concentration (Cmax), time to Cmax (Tmax), and AUC0–last (area under the concentration-time curve until the last plasma concentration that was below the limit of quantitation) for morphine levels were determined from a plasma sample at 0, 5, 10, 15, and 30 minutes, and 1, 4, 8, 12, 24, 36, 48, and 72 hours. Drug effects including pain, analgesic use, and side effects were measured for 72 hours after cesarean delivery. RESULTS: Epidural lidocaine administration (20–35 mL) 1 hour before epidural EREM administration increased the Cmax in group E (11.1 ± 4.9) compared with group SE (8.3 ± 7.1 ng/mL) (P = 0.038). There were no significant effects on Tmax and AUC0–last of venous morphine between the groups (P > 0.05). There was an increased incidence in vomiting, oxygen use, and hypotension in group E (patients who received lidocaine before EREM). CONCLUSION: A large dose of epidural lidocaine 1 hour before EREM administration alters the pharmacokinetics and drug effects of EREM. Clinicians must apply caution when EREM is administered even 1 hour after an epidural lidocaine “top-up” for cesarean delivery.

Intranasal Fentanyl for Breakthrough Pain Control

Breakthrough pain (BTP) is experienced by approximately 65% of children and adults with chronic pain. Undiagnosed or untreated BTP produces negative emotional, physical, and economic consequences. BTP episodes have a rapid onset and short duration. Short acting oral opioids are the cornerstone of BTP management. Oral medications available to treat BTP episodes like immediate-release morphine or oxycodone have a delayed onset of action so that there is a mismatch between the episode of BTP and the effect of the oral opioids. Novel fentanyl delivery systems for BTP offer pharmacokinetic properties that match the time profile of BTP. Among the transmucosal routes, intranasal fentanyl has gained popularity due to its high bioavailability, rapid onset of action, high potency, short duration, and ease of administration. Its efficacy and safety have been demonstrated in adults who are opioid tolerant. Although children with chronic cancer pain also experience BTP, there is paucity of data on the use of intranasal fentanyl for BTP in this age group.

Randomized, Double-Blind, Placebo-Controlled, Single Intravenous Dose-Escalation Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of the Novel Coronary Smooth Muscle Cell Proliferation Inhibitor Biolimus A9 in Healthy Individuals

Biolimus A9 (BA9) is a novel proliferation inhibitor of coronary smooth muscle cells that has been specifically designed for coating drug‐eluting stents. The goals of this study were to identify the highest safe intravenous dose of BA9, to evaluate the dose‐dependent pharmacokinetics of BA9 after intravenous administration in humans, and to characterize early clinical symptoms of BA9 toxicity in healthy subjects. This phase 1 trial in healthy subjects was designed as a double‐blind, placebo‐controlled, randomized, ascending single‐dose study. After screening and randomization, 28 volunteers received either placebo (n = 7) or BA9 (n = 21) in a double‐blinded fashion. Doses from 0.0075 mg/kg were escalated to 0.25 mg/kg in 4 cohorts. BA9 concentrations were measured using liquid chromatography‐tandem mass spectrometry. BA9 doses up to 0.075 mg/kg were well tolerated. Only the highest BA9 dose of 0.25 mg/kg produced reversible drug‐related adverse events. The most frequent adverse events were headache, nausea, and mouth ulcers, most likely due to immunosuppression. Exposure to BA9 did not result in electrocardiographic or clinical laboratory changes. BA9 had a terminal half‐life of 90.0 ± 40.0 hours (all n = 21, mean ± standard deviation), an apparent clearance from blood of 0.96 ± 1.07 L/kg/h, and a volume of distribution of 96.5 ± 72.6 L/kg.

Quantification of the 5-lipoxygenase inhibitor zileuton in human plasma using high performance liquid chromatography–tandem mass spectrometry

Zileuton is an orally active, selective inhibitor of 5-lipoxygenase, which catalyzes the first step in the conversion of arachadonic acid into leukotrienes. Given the important role of leukotrienes in inflammation and cell signaling, multiple studies have investigated the efficacy of zileuton in the treatment of human disease. Examples of disease targets include asthma, ulcerative colitis, rheumatoid arthritis, and more recently, acne, ischemic/reperfusion injury, inflammatory pain, and sickle cell anemia. Zileuton is currently approved for the prophylaxis and chronic treatment of asthma. We report the development and validation of a sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the quantification of zileuton in human EDTA plasma. The range of reliable response was 3.05-20,000ng/mL in human plasma. The calibration curves had a correlation coefficient of r(2)>0.99. The intra-day precision was 3.4-5.3%. The inter-day precision ranged from 4.5% to 7.3% and inter-day accuracy from 100% to 107%. No matrix interferences, ion suppression/enhancement, or carry-over was observed. The assay met all predefined acceptance criteria and was subsequently employed to measure plasma zileuton concentrations in a clinical trial.

Intraoperative Monitoring in Tethered Cord Surgery

The tethered cord syndrome is caused by abnormal fixation of the spinal cord with resultant reduction in blood flow leading to impaired oxidative metabolism of the grey matter. Etiologies include embryological derangement, trauma, and surgery. Common symptoms include but are not limited to pain, weakness, loss of sensation, and bowel/bladder dysfunction. Surgical release allows normalization of blood flow and then parallel neurological improvement. Goals of neurosurgery to correct tethered cord are full release of restricted tissue and preservation of involved neural structures. Because of difficulty identifying neural elements based on anatomic appearance, multimodality neurophysiologic monitoring is employed to minimize risk and preserve function, especially bowel and bladder control. A technique using spontaneous and evoked electromyography, somatosensory-evoked potentials, motor-evoked potentials, bulbocavernosus reflex elicitation, and bladder pressure urometry was successfully integrated into the surgical release of this patient’s tethered cord.

Electrophysiological Monitoring During Thoracic Aortic Aneurysm Surgery

Intraoperative monitoring (IOM) of the central nervous system during surgery to repair aneurysms of the thoracoabdominal aorta (TAA) is an area of significant inquiry due to the substantial incidence of neurological injury with surgery. The incidence of paralysis varies with the surgical, interventional, or hybrid procedure used. It is clear that the risk of perioperative paralysis also varies due to a substantial number of nonsurgical factors, including changes in the vascular perfusion resulting from surgery, the specific patient anatomy, and patient comorbidities. This chapter will review the surgical techniques and the IOM techniques utilized.