Selection and Biosensor Application of Aptamers for Small Molecules

Small molecules play a major role in the human body and as drugs, toxins, and chemicals. Tools to detect and quantify them are therefore in high demand. This review will give an overview about aptamers interacting with small molecules and their selection. We discuss the current state of the field, including advantages as well as problems associated with their use and possible solutions to tackle these. We then discuss different kinds of small molecule aptamer-based sensors described in literature and their applications, ranging from detecting drinking water contaminations to RNA imaging.

Therapeutic drug monitoring in dried blood spots using liquid microjunction surface sampling and high resolution mass spectrometry

Dried blood spots (DBS) are a versatile and stable tool for direct clinical blood analysis. We demonstrate the utility of liquid microjunction surface sampling technology in combination with an Orbitrap mass spectrometer for direct quantification of multiple drugs in DBS.

Validation of a liquid chromatography method for the simultaneous determination of several nonsteroidal anti-inflammatory drugs in human plasma for therapeutic drug monitoring

BACKGROUND

Diflunisal, naproxen, ketoprofen, etodolac, mefenamic acid, rofecoxib, and celecoxib are nonsteroidal anti-inflammatory drugs, which have analgesics, antipyretics, and anti-inflammatory activities. The aim of this work was to develop and validate a simple assay that could be implemented in most laboratories for the purpose of clinical and toxicological screening, pharmacokinetic studies, and in therapeutic drug monitoring.

METHODS

A new and simple high-performance liquid chromatography assay was developed and validated for the simultaneous determination of the above-mentioned drugs in small samples of human plasma (0.25 mL). After protein precipitation with acetonitrile, satisfactory separation was achieved on a Hypersil BDS C18 column (250 × 4.6 mm, 5 m) using a mobile phase comprising 20 mmol/L ammonium phosphate buffer (pH = 3) and acetonitrile at a ratio of 35:65, vol/vol; the elution was isocratic at ambient temperature with a flow rate of 1 mL/min. The UV detector was set at 265 nm.

RESULTS

The method was validated according to the recommendations of the Food and Drug Administration, including assessment of linearity, selectivity, precision, accuracy, and stability in human plasma. The use of betamethasone dipropionate as internal standard improved accuracy and precision. Response was linear over the calibration ranges. The limits of quantification were 0.2 g/mL for diflunisal and naproxen, 0.05 g/mL for ketoprofen, 0.1 g/mL for etodolac and mefenamic acid, and 0.02 g/mL for celecoxib and rofecoxib. The percent coefficient of variation for the QCs and the limit of quantification were within 10%, and the accuracies ranged between 96% and 106% for all the analytes. Mean drug recovery values were in the range of 95%-98% and 90.0% for all analytes and internal standard, respectively. All the analytes were stable in frozen plasma over a period of 3 months at -80°C.

CONCLUSIONS

This assay method was valid within a wide range of plasma concentrations and may be proposed as a suitable method for pharmacokinetic studies, therapeutic drug monitoring implementation, and routine clinical applications and suitable for special populations of patients who receive a combination of these drugs.

Utilization of pharmacogenomics and therapeutic drug monitoring for opioid pain management

Aims: The use of medication in pain management currently involves empirical adjustment based on observed clinical outcome and the presence of adverse drug reactions. In this study, pharmacogenomics and therapeutic drug monitoring were used to evaluate the clinical effectiveness of genotyping chronic pain patients on analgesic therapy. It was hypothesized that patients who have inherited polymorphisms in CYP2D6 that make them poor or intermediate metabolizers of opioid medications would have higher steady-state concentrations of those opioids and may be more likely to experience adverse drug reactions. Materials & Methods: In an attempt to investigate the relationship between the polymorphic enzymes, steady-state drug concentrations, therapeutic effects and side effects, 61 patients were clinically evaluated and genotyped, and drug concentrations were measured and outcomes analyzed. Samples were collected and DNA extracted from whole blood using a Puregene® DNA isolation kit. CYP2D6 genotyping (*3, *4, *5, *6, *7, *8 and gene duplication) were carried out using Pyrosequencing®. Steady-state plasma concentrations of methadone, oxycodone, hydrocodone and tramadol were determined by HPLC tandem mass spectrometry. Results: The results demonstrated the prevalence of CYP2D6 polymorphisms in the population undergoing pain management was not statistically different from the general population. The majority of the pain patients (54%) were extensive metabolizers; 41% were intermediate metabolizers and 5% poor metabolizers. Poor metabolizers in general tended to have the highest steady-state drug concentrations compared with extensive metabolizers (poor metabolizers > intermediate metabolizers > extensive metabolizers) although this wasn’t statistically significant. Also, a relationship between oxycodone steady-state drug concentrations and pain relief was found. A total of 80% of patients reporting adverse drug reactions also had impaired CYP2D6 metabolism. The remaining 20% with adverse drug reactions had other cofactors (i.e., drug–drug interactions) that could explain the toxicity. Conclusion: These results suggest that patient care may be improved by genotyping and following therapeutic drug concentrations. Benefits include increased efficiency in proper drug selection, dose optimization and minimization of adverse drug reactions to improve patient outcome and safety. In addition, this study clearly demonstrated a relationship between oxycodone steady-state drug concentrations and pain relief. Future large-scale prospective studies are needed to confirm the clinical value of using genetic information to guide pain management therapy.

Laboratory Monitoring of OxyContin (Oxycodone): Clinical Pitfalls

Some patients have headaches that are refractory to standard treatments, and they require chronic administration of opioid analgesics. The use of opioids in a clinical setting must be closely monitored due to the medications' potential for addiction, abuse, and fatal interactions. Limited access to opioids and the demand for them outside the clinical setting leads to another danger. Patients can mislead their providers into prescribing opioids, intending to sell the medications instead of using them to alleviate their own pain. For protection of the patient, as well as the community, it is vital that such activity be prevented. We recently encountered a patient we suspected of abusing or misusing OxyContin (oxycodone). In order to determine whether the patient was taking the medication as prescribed, we ordered a urine-based immunoassay drug screen. The results were negative; the patient appeared to not have oxycodone in his system. Based on these results, we dismissed the patient from our practice. At the patient's request, a second test was performed, this time using gas chromatography-mass spectrometry. It indicated that the patient did indeed have sufficiently high levels of oxycodone in the urine. The minimum level threshold was too high to detect the presence of oxycodone in the immunoassay. We would like to help prevent future misunderstandings such as we experienced. To do so, we will first present the case of our patient, followed by a discussion of the actions taken. Finally, we will provide an overview of analgesic monitoring systems.

A Rapid and Simultaneous Determination of Several Analgesic Antiinflammatory Agents by Capillary Zone Electrophoresis

A rapid and simultaneous determination of several analgesic antiinflammatory agents--ibuprofen, acetaminophen, indomethacin, and salicylic acid--in human serum was developed by using capillary zone electrophoresis (CZE) coupled with diode-array ultraviolet detection. After precipitation of serum protein with acetonitrile containing 3-isobutyl-1-methylxanthine as the internal standard, an aliquot of deproteinized samples was applied directly to the CZE system. It enabled us to measure all of these four agents within 6 min, and there were no peaks interfering with the assay of these agents or 3-isobutyl-1-methylxanthine. Both the separation and quantification of these agents in human serum were reproducible after repeated analysis within a day or day-to-day analysis. In addition, there was a good correlation for each drug (r = 0.997-0.999) between the values in serum determined by CZE analysis and those measured either by high-performance liquid chromatography with ultraviolet detection (ibuprofen and indomethacin) or by fluorescence polarization immunoassay (acetaminophen and salicylic acid). Therefore, the present CZE analysis could provide a simple, rapid, and efficient method for the identification as well as monitoring of analgesic antiinflammatory agents, particularly in serum of patients suffering from intoxication by overdosage of these agents.

Systematic toxicological analysis procedures for acidic drugs and/or metabolites relevant to clinical and forensic toxicology and/or doping control

This paper reviews systematic toxicological analysis (STA) procedures for acidic drugs and/or metabolites relevant to clinical and forensic toxicology or doping control using gas chromatography, gas chromatography-mass spectrometry, liquid chromatography, thin-layer chromatography and capillary electrophoresis. Papers from 1992 to 1998 have been taken into consideration. Screening procedures in biosamples (whole blood, plasma, serum, urine, vitreous humor, brain, liver or hair) of humans or animals (horse, or rat) are included for the following drug classes: angiotensin-converting enzyme (ACE) inhibitors and angiotensin II (AT-II) blockers, anticoagulants of the 4-hydroxy coumarin type, barbiturates, dihydropyridine calcium channel blockers (calcium antagonists), diuretics, hypoglycemic sulfonylureas and non-steroidal anti-inflammatory drugs (NSAIDs). Methods for confirmation of preliminary results obtained by screening procedures using immunoassay or chromatographic techniques are also included. Furthermore, procedures for the simultaneous detection of several drug classes are reviewed. The toxicological question to be answered and the consequences for the choice of an adequate method, the sample preparation and the chromatography itself are discussed. The basic information about the biosample assayed, work-up, separation column, mobile phase or separation buffer, detection mode and validation data of each procedure is summarized in 16 tables. They are arranged according to the drug class and the analytical method. Examples of typical applications are presented. Finally, STA procedures are reviewed and described allowing simultaneous screening for different (acidic) drug classes.