A novel nanozyme doped ZnO/r-GO-based sensor for highly sensitive electrochemical determination of muscle-relaxant drug: cyclobenzaprine HCl.

A nanocomposite of Ce-doped ZnO/r-GO was synthesized using a conventional hydrothermal method. The synthesized nanocomposites were utilized for the purpose of sensitive and selective detection of cyclobenzaprine hydrochloride (CBP). The properties of the composite were extensively analyzed, including its morphology, structure, and electrochemical behavior. This study investigates the application of a modified glassy carbon electrode for the detection of CBP, a muscle relaxant used to treat musculoskeletal diseases that cause muscle spasms. The electrode is modified with Ce-doped ZnO/r-GO. Various detection methods, such as cyclic voltammetric and square wave techniques (SWV), were utilized. The composite material showed high effectiveness as an electron transfer mediator in the oxidation of CBP. The electrode showed a good response for SWV evaluations in CBP identification, with a minimum detection limit of 1.6 × 10-8 M and a wide linear range from 10 × 10-6 M to 0.6 × 10-7 M, under ideal conditions. The rate constant for charge transfer (ks) and the estimation of the electrochemical active surface area were obtained. A developed sensor exhibited desirable selectivity, long-lasting stability, and remarkable reproducibility. A sensor was used to analyze water, human serum, and urine samples, resulting in positive recovery results.

Green analytical chromatographic assay method for quantitation of cyclobenzaprine in tablets, spiked human urine and in-vitro dissolution test.

Cyclobenzaprine hydrochloride, a skeletal muscle relaxant has been determined using an ecofriendly micellar HPLC method in its pure form and tablets. The chromatographic determination was performed using C8 monolithic column (100mm×4.6mm i.d., 5µm particle size) and micellar eluent which was composed of sodium dodecyl sulfate (0.15M), n-propanol (15%), 0.02M orthophosphoric acid (pH 4.5) and 0.3% triethylamine using UV detection of effluent was set at 225nm. The calibration plot showed good linearity over concentration range from 2-40µg/mL. The assay results were statistically validated for linearity, accuracy, precision and specificity according to ICH guidelines. Additionally, regarding USP guidelines, the uniformity of tablets content and in-vitro dissolution test of the tablets was tested using the proposed method. Simple and rapid applicability of the developed method allowed determination of the drug in its pure and tablet dosage forms. Moreover, the major advantage of micellar HPLC technique is to determine the drug in biological fluids without prior extraction steps. Depending on this, the estimation of cyclobenzaprine in spiked human urine was so simple without traditional tedious procedures. The proposed method offers the advantages of sensitivity and simplicity in addition to short analysis time which didn't exceed 6 minutes.

Stability of sufentanil and baclofen mixtures for intrathecal analgesia at different concentrations in polypropylene syringes.

BACKGROUND: Intrathecal analgesia is a method using various molecules alone or in combination. Among these, the association sufentanil/ baclofen is widely used. Instead of moving patients to the few expert centers taking charge of these specific preparations, it could be better to transport syringes to peripheral centers managing pump refilling. That is why, it is interesting to demonstrate the stability of the mixture, and so to be able to ensure the best transport conditions of syringes. METHODS: A stability indicating UPLC-DAD method was developed and validated according to the ICH guidelines. Four mixtures of sufentanil baclofen stored in 5±3°C and 25±2°C were evaluated for seven days and compared to the initial observed concentrations. RESULTS: The stability is demonstrated only for preparations stored at 5±3°C for seven days thanks to relative concentrations (95% confidence intervals of the mean of 3 samples) systematically positioned between 90% and 110%. On the other hand, after few days, degradation products of sufentanil appeared for all mixtures stored at 25°C±2°C. CONCLUSION: This study shows the stability of a weakly and a highly concentrated mixture of sufentanil and baclofen solutions in polypropylene syringes stored at 5±3°C for seven days. This result will allow the transport of the preparation under optimal conditions. Advance preparations for intrathecal pump refills could also be feasible.

[Lethal intoxication with baclofen].

The objective of the present study was to select and develop simpler methods for the quantitative determination of baclofen in blood with the use of HPLC and tandem MS (MS-MS) techniques and its qualitative determination in cadaveric organs by the GC/MS technique. These mathods were shown to be suitable for the purpose of forensic medical analysis, clinical, toxicological, and therapeutic monitoring. The special emphasis is laid on the methods used to investigate the biological materials obtained from the subjects who died from baclofen intoxication.

Multivariate optimization of separation conditions for simultaneous determination of acemetacin and chlorzoxazone in a pharmaceutical preparation by HPLC using response surface methodology.

A new, fast, accurate, precise, and sensitive RP-HPLC method for the simultaneous determination of acemetacin and chlorzoxazone has been developed. Response surface methodology with a central composite design was used to optimize the acetonitrile and ammonium acetate percentage in the mobile phase and pH of ammonium acetate. The optimum separation was achieved on a C18 column (250 x 4.6 mm id, 5 microm particle size) using the mobile phase methanol-acetonitrile-0.02 M ammonium acetate, pH 9.4 (25 + 35 + 40, v/v/v) at a flow rate of 1.5 mL/min; UV detection at 270 nm, and cyanocobalamin as an internal standard. This developed method was validated and successfully applied to a coated tablet pharmaceutical preparation.

Development and validation of a simple LC method for the determination of phenacetin, coumarin, tolbutamide, chlorzoxazone, testosterone and their metabolites as markers of cytochromes 1A2, 2A6, 2C11, 2E1 and 3A2 in rat microsomal medium.

Cytochrome P450 enzymes are responsible for the oxidative metabolism of most pharmaceutical compounds. A "cocktail" approach which employs simultaneous administration of a mixture of substrates of CYP enzymes was often used to assess the metabolic activity of multiple P450 forms in one experiment. Phenacetin, coumarin, tolbutamide, chlorzoxazone and testosterone are commonly used as probe substrates to evaluate cytochrome P450 function. An analytical strategy to simultaneously extract and analyze the five probe substrates and their major metabolites by HPLC-DAD was developed. The incubation was done with all the substrates in one step. The ten analytes were extracted simultaneously by solid-phase extraction (SPE) from rat liver microsomes. A C18 analytical column and mobile phase composed of acetonitrile and 0.02% aqueous phosphoric acid were used for the chromatographic separation with DAD detection. Limits of quantification varied between 0.02378 and 0.2361 microg/mL which contributed to quantify all these drugs and metabolites with UV detection. The method is applicable for the modeling and description of pharmacological interactions on rat cytochromes P450 or can be used for in vitro evaluation of cytochromes 1A2, 2A6, 2C11, 2E1 and 3A2.

Human pharmacokinetics of the muscle relaxant, eperisone hydrochloride by liquid chromatography-electrospray tandem mass spectrometry.

Eperisone hydrochloride (4'-ethyl-2-methyl-3-piperidinopropiophenone hydrochloride) is a muscle relaxant agent, widely used in the treatment of patients with muscular contractures, low back pain or spasticity. Because of its mechanism of action (inhibition of gamma-efferent firing and local vasodilatation activity), side effects on central nervous system are rarely observed. A sensitive liquid chromatography-electrospray ionization-mass spectrometry method for determination of eperisone in human plasma has been developed, with a lower limit of quantification of 0.01 ng/mL. The method was applied to a pharmacokinetic study in 12 healthy volunteers given eperisone 100 mg as single dose on day 1 and three times daily on days 2 to 4. Eperisone was rapidly absorbed after oral administration (T (max) = 1.6 h) as it was expected by its fast-onset relaxant activity. Moreover, eperisone underwent a rapid elimination from the body (biological half-life 1.87 h), which was not modified during the repeated dosing as suggested by the C (max) cumulation observed, not different from that expected for a t (1/2) of 1.87 h as suggested by the similar and negligible plasma concentration values (0.063 and 0.067 ng/mL) measured on day 4 before the morning dose and 12 h after evening dose, thus ruling out any potential risk for drug accumulation. Thus, the pharmacokinetic characteristics of eperisone provide further justification for its tolerability in patients with low back pain or spastic palsy, in which the drug is given for periods ranging from few days to several months, respectively.

Development and Validation of a Stability-Indicating High-Performance Liquid Chromatographic Method for the Quantification of Methocarbamol and Its Impurities in Pharmaceutical Dosage Forms.

A novel, delicate, stability-indicating, gradient, reversed-phase high-performance liquid chromatographic method has been established for the quantitative estimation of methocarbamol (MTC) and its impurities present in a pharmaceutical oral suspension. XBridge C18, 5 µm, 250 mm × 4.6 mm column was used to accomplish chromatographic separation with a buffered mobile phase consisting of a mixture of 0.01 M of sodium dihydrogen phosphate (pH 7.0 buffer) and methanol in the ratio of 95:05 (v/v), respectively, were used as solvent A and a mixture of methanol and Milli-Q water in the ratio 90:10 (v/v), respectively, was used as solvent B. Analysis was carried out at 0.8 mL/min flow rate and the detection wavelength at 225 nm. The compartment temperature of the column is put at 25°C. The resolution of MTC and its four impurities has been attained >2.0 for all pairs of compounds. Significant degradation of MTC was photolytic, thermal and oxidative stress conditions. Validation of the developed method was performed as stated by the International Conference on Harmonization guidelines with regard to all validation parameters like specificity, accuracy, linearity, precision, limit of detection, limit of quantitation and robustness.

A stability-indicating high-performance liquid chromatographic method for the determination of methocarbamol in veterinary preparations.

An isocratic HPLC method was developed and validated for the quantitation of methocarbamol in the presence of its degradation products. Quantitation was achieved using a reversed-phase C18 column at ambient temperature with mobile phase consisting of methanol-water-tetrahydrofuran (25 + 65 + 10, v/v). The flow rate was 0.9 mL/min. The detection was by UV light at 274 nm. The proposed method was validated for selectivity, precision, linearity, and accuracy. The assay method was found to be linear from 159.0 to 793.2 microg/mL (3.2 to 15.9 microg injected). All validation parameters were within the acceptable range. The developed method was successfully applied to estimate the amount of methocarbamol in a veterinary injection.

A comparative study of sterically and electro-statically stabilized silver nanoparticles for the determination of muscle relaxant tizanidine: Insights of localized surface plasmon resonance, surface enhanced Raman spectroscopy and electrocatalytic activity.

A comparative study of two types of silver nanoparticles was investigated. The effect of the surface chemistry of the studied silver nanoparticles (AgNPs) on their localized surface plasmon resonance was utilized for the quantitative determination of muscle relaxant tizanidine drug. The studied AgNPs are classified according to the type of stabilizing agent used in their synthesis into electrostatically and sterically stabilized AgNPs. The electrostatically-stabilized AgNPs (AA AgNPs) were prepared using ascorbic acid as both reducing and protective agents in alkaline medium. The sterically-stabilized AgNPs type (PEG-AA AgNPs) was prepared using ascorbic acid as a reducing agent and polyethylene glycol as a stabilizing agent at room temperature. The interaction of tizanidine with AgNPs was characterized using four different techniques including, transmission electron microscope, UV-visible spectrophotometric, surface enhanced Raman spectroscopic (SERS) and electroanalytical methods. SERS method was developed to study the relationship between the plasmon resonance and the enhanced power of Raman signal. The electrocatalytic behavior and the interfacial properties of AgNPs were studied using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) on glassy carbon electrode modified with AgNPs. The quantitative determination of tizanidine in pharmaceutical and biological samples was successfully achieved by using AgNPs probe based on spectrophotometric methods. A linear response over the range 10-400 nmol L-1 was obtained. Validation procedures were carried out following International Conference on Harmonization (ICH) guidelines.

[Exploration of quality control of inorganic elements in Chinese herbal medicines for stimulating blood circulation and relaxing muscles and joints by atomic absorption spectrophotometry].

Researches have shown the close relationships between inorganic elements and curative efficiencies of various Chinese herbal medicines. Yet, in studies of chemical composition and quality control of Chinese herbal medicines for stimulating blood circulation and relaxing muscles and joints, inorganic substances are often overlooked. In order to improve and reestablish the standard of quality control of Chinese herbal medicines, the authors attempted a method that would incorporate the composition of inorganic elements as part of the quality control. In the present study, the authors used atomic absorption spectrophotometry to measure the contents of fifteen inorganic elements, namely, Cu, Ca, Fe, K, Mg, Mo, Ni, Sr, V, Mn, Zn, Na, Cr, Cd, and Hg, in several Chinese herbal medicines, including Da Huo Luo Wan. The authors then discussed the relationship between these inorganic elements and curative efficiencies of these Chinese herbal medicines. By comparing the levels of inorganic elements found in Da Huo Luo Wan with those found in other Chinese herbal medicines used in the study, it was revealed that trace elements, Fe, Cu, Mn, and Zn, contribute to the curative efficiency of Da Huo Luo Wan. The authors' results showed that the amounts of trace elements Fe, Cu, Mn and Zn found in Chinese herbal medicine Da Huo Luo Wan are related to the following curative effects of Da Huo Luo Wan: relieving rheumatism, rectifying breathing and alleviating phlegm, stimulating blood circulation and relaxing muscles and joints. The measurement and analysis of inorganic elements in Da Huo Luo Wan will also provide evidences and references for the fingerprint establishment of Da Huo Luo Wan in the future.

FTIR assay method for UV inactive drug carisoprodol and identification of degradants by RP-HPLC and ESI-MS.

A new method of analysis has been developed for UV inactive drug carisoprodol using FTIR spectroscopy. These methods were validated for various parameters according to ICH guidelines. The proposed method has also been successfully applied for the determination of the drug concentration in a tablet formulation. The method proved to be accurate (mean percentage recovery between 95 and 105%), precise and reproducible (relative standard deviation<2%), while being simple, economical and less time consuming than other methods and can be used for routine estimation of carisoprodol in the pharmaceutical industry. The developed method also implicates its utility for other UV inactive substances. The stability of the drug under various stress conditions was studied and the drug was found to be particularly susceptible to alkaline hydrolysis. Degradation products of the alkaline hydrolysis were detected by RP-HPLC and tentatively identified by ESI-MS.

A fatality involving metaxalone.

A case is presented of a 54-year-old white female found dead in a secured apartment. Postmortem toxicologic analysis of the heart blood identified acetaminophen (97 mg/L), citalopram (0.4 mg/L), gabapentin (24 mg/L) and metaxalone (21 mg/L). The metaxalone concentration is within the range of previously reported fatalities involving metaxalone. The medical examiner ruled that the cause of death was metaxalone and gabapentin intoxication and the manner of death was suicide.

Application of normalized spectra in resolving a challenging Orphenadrine and Paracetamol binary mixture.

Normalized spectra have a great power in resolving spectral overlap of challenging Orphenadrine (ORP) and Paracetamol (PAR) binary mixture, four smart techniques utilizing the normalized spectra were used in this work, namely, amplitude modulation (AM), simultaneous area ratio subtraction (SARS), simultaneous derivative spectrophotometry (S(1)DD) and ratio H-point standard addition method (RHPSAM). In AM, peak amplitude at 221.6nm of the division spectra was measured for both ORP and PAR determination, while in SARS, concentration of ORP was determined using the area under the curve from 215nm to 222nm of the regenerated ORP zero order absorption spectra, in S(1)DD, concentration of ORP was determined using the peak amplitude at 224nm of the first derivative ratio spectra. PAR concentration was determined directly at 288nm in the division spectra obtained during the manipulation steps in the previous three methods. The last RHPSAM is a dual wavelength method in which two calibrations were plotted at 216nm and 226nm. RH point is the intersection of the two calibration lines, where ORP and PAR concentrations were directly determined from coordinates of RH point. The proposed methods were applied successfully for the determination of ORP and PAR in their dosage form.

Liquid chromatography in pharmaceutical analysis IX: Determination of muscle relaxant--analgesic mixtures using normal phase chromatography.

High-pressure liquid chromatography was used to optimize the resolution of eight widely prescribed therapeutic agents commonly found in muscle relaxant--analgesic mixtures. The compounds were chromatographed on normal phase porpous silica or cyanopropylsilane columns, using various solvent systems paired on the basis of Synder's solvent selectivity scheme to give a polarity index for each system of 3.3. A carisoprodol, phenacetin, and caffeine mixture was selected to demonstrate the utility of the separation and quantification method. The mixture was chromatographed on a porous silica column, using tetrahydrofuran--toluene (50:50) at a flow rate of 2.0 ml/min. Each determination can be achieved in approximately 8 min with an accuracy of 3--5%.

Liquid chromatography in pharmaceutical analysis XI: determination of muscle relaxant--analgesic mixture using reversed-phase and ion-pair techniques.

High pressure liquid chromatography using reversed-phase and/or ion-pair techniques was used to optimize resolution of aspirin-containing muscle relaxant mixtures as well as other therapeutic agents commonly found in muscle relaxant-analgesic mixtures. The compounds were chromatographed on an octadecylsilane column using methanol--water solvent systems, some of which contained tetrabutylammonium cation as counterion. Mixtures of methocarbamol--aspirin and chlorzoxazone--acetaminophen were selected to demonstrate separation and quantification. The methocarbamol--aspirin mixture was chromatographed with methanol--water (40:60, pH 6.8) containing 0.01 M tetrabutylammonium cation at a flow rate of 2.0 ml/min. The chlorzoxazone--acetaminophen mixture was chromatographed with methanol--water (50:50) at a 2.0 ml/min flow rate. The separation and quantitation of each mixture were achieved in approximately 8 min with accuracy in the 2--3% range.

Application of derivative-differential UV spectrophotometry and ratio derivative spectrophotometric determination of mephenoxalone and acetaminophen in combined tablet preparation.

A method is presented for the direct determination of mephenoxalone and acetaminophen in combined pharmaceutical dosage forms without prior separation. The first method, derivative-differential spectrophotometry, comprised of measurement of the difference absorptivities derivatized in the first order (deltaD1) of a tablet extract in 0.1 N NaOH relative to that of an equimolar solution in methanol at wavelengths of 289.6 and 252.6 nm respectively. The second method is based on ratio derivative spectrophotometry. The amplitudes in the first derivative of the ratio spectra at 233.5 and 288.9 nm were selected to determine mephenoxalone and acetaminophen in the mixture. The proposed methods, which give thoroughly comparable data, are simple and rapid, and allow one to obtain precise and accurate results.

The rapid quantitative analysis of phenprobamate and acetaminophen by RP-LC and compensation technique.

For the analysis of phenprobamate and acetaminophen in combination, the main analytical methods used were spectrophotometric compensation technique and Vierordt's method with high performance liquid chromatography, used as an analytical reference method. The first procedure for the simultaneous quantitative determination phenprobamate and acetaminophen by high performance liquid chromatographic (HPLC) method was proposed. The method was standardized using a LiChrosorb RP18-5 column, methanol-water-formic acid (120:80:1 v/v), apparent pH 4.25 with triethylamine, as mobil phase and UV detection at 254 nm. The peak area response versus concentration was linear in a concentration range from 4 to 28 microg ml(-1) of phenprobamate and from 4 to 30 microg ml(-1) for acetaminophen. The correlation coefficients were 0.9999 for phenprobamate and 0.9987 for acetaminophen. The second procedure, based on the compensation technique, is presented for the derivative spectrophotometric determination of binary mixtures with overlapping spectra. The proposed methods, which give thoroughly comparable data, are simple and rapid and allow precise and accurate results.

Metaxalone (Skelaxin)-related death.

The case history and toxicological findings of a fatal multi-drug overdose involving metaxalone (Skelaxin) are presented. Gas-liquid chromatography with flame-ionization detection and gas chromatography-mass spectrometry were used to determine the following drug concentrations (mg/L) in aortic blood: 19 mg/L metaxalone; 190 mg/L acetaminophen; 0.28 mg/L hydrocodone; and < 0.1 mg/L diazepam, nordiazepam, amitriptyline, and nortriptyline. The following concentrations of metaxalone were reported in alternate specimens: 17 mg/L in femoral blood; 44 mg/L in bile; 70 mg/kg in liver; 7 mg/L in urine; 202 mg/kg in gastric contents; and 14 mg/L in vitreous humor. These concentrations were determined using both direct extraction and the method of standard addition. The quantitative results obtained by both procedures were in good agreement. Because of the limited information published on metaxalone toxicity, the pathologist assigned the manner and cause of death as accidental acute hydrocodone intoxication. Four additional cases in which metaxalone was present were analyzed for comparison. Two cases were probable drug-related deaths and had metaxalone aorta blood concentrations of 18 and 11 mg/L. The other two cases had therapeutic metaxalone concentrations in the aortic blood of < 0.75 and 2.1 mg/L.

Potential interference of cyclobenzaprine and norcyclobenzaprine with HPLC measurement of amitriptyline and nortriptyline: resolution by GC-MS analysis.

Cyclobenzaprine and its major metabolite, norcyclobenzaprine, differ from amitriptyline and nortriptyline only by the presence of a double bond in the cycloheptane ring. Three patients developed sufficient levels of cyclobenzaprine and norcyclobenzaprine because of either rapid or long-term ingestion of cyclobenzaprine to cause positive interferences in both a Syva EMIT assay and a high-performance liquid chromatographic (HPLC) assay for identification and quantitation of tricyclic antidepressants in serum. Cyclobenzaprine coeluted with amitriptyline, and norcyclobenzaprine eluted slightly earlier than, but was poorly resolved from, nortriptyline in this HPLC assay. We found that cyclobenzaprine could be distinguished from amitriptyline and that norcyclobenzaprine could be distinguished from nortriptyline on the basis of gas chromatographic retention times upon gas chromatographic-mass spectrometric analyses after derivatization with trifluoroacetic anhydride. The compounds were also distinguishable by mass spectrometric criteria.