Development and validation of an HPLC-DAD method for bis(12)-hupyridone and its application to a pharmacokinetic study

A rapid and simple method of high performance liquid chromatography with UV detection for the quantification of bis(12)-hupyridone in rat blood has been developed and validated. Chromatographic separation was carried out in an Agilent Extend C₁₈ 5 μm column (length, 250 mm; inner diameter, 4.6 mm) using a mixture of water–acetonitrile–trifluoroacetic acid (81:19:0.04, v/v/v) as the mobile phase at a flow rate of 1 mL/min, with detection at 229 nm. The method used for the bis(12)-hupyridone quantification showed linearity for concentration range of 0.1–7.5 μg/mL with r² = 0.9991. The limit of detection and quantification of this method were 0.05 μg/mL and 0.1 μg/mL, respectively. The intra- and inter-day variations of the analysis were less than 4.22% with standard errors less than 13.3%. The developed method was successfully applied to the pharmacokinetic study of bis(12)-hupyridone after intravenous administration of 5 mg/kg and intraperitoneal administration of 10 and 20 mg/kg in rats.     

Development of a validated liquid chromatographic method for determination of related substances of telmisartan in bulk drugs and formulations

A simple and rapid reversed phase liquid chromatographic method for separation and determination of the related substances of telmisartan (TLM) was developed and validated. The chromatographic separation was achieved on Lichrospher RP-18 column (250 × 4.6 mm, 5 μm), using 20 mM ammonium acetate containing 0.1% (v/v) triethylamine (pH adjusted to 3.0 with trifluoroacetic acid) and acetonitrile as mobile phase at 25 °C. The detection was performed at 254 nm. The method was validated and found to be robust, precise, specific and linear between 0.37 and 500 μg/mL. The limits of detection and quantification of telmisartan were 0.11 and 0.37 μg/mL, respectively. The method was successfully applied to quantify related substances and assay of TLM in bulk drugs and commercial tablets. The related substances relate to a novel synthetic route and different from those A-H impurities reported by European Pharmacopeia.     

Pharmacokinetic interactions between efavirenz and rifampicin in HIV-infected patients with tuberculosis

OBJECTIVE: To evaluate the pharmacokinetic interactions between efavirenz and rifampicin (rifampin) in patients with HIV infection and tuberculosis. DESIGN: Nonblind, randomised, pharmacokinetic study. PATIENTS: 24 patients (21 male, 3 female; mean age 37 years) with HIV infection and tuberculosis. INTERVENTIONS: Patients were randomised to one of the following treatments: group A (n = 16) received antituberculosis drugs without rifampicin, plus highly active antiretroviral therapy (HAART) including efavirenz 600 mg once daily, on days 1 to 7. Patients were then switched to rifampicin in bodyweight-adjusted fixed-dose combination plus HAART including efavirenz 600 mg once daily (group A-1; n = 8) or efavirenz 800 mg once daily (group A-2; n = 8). Group B (n = 8) received rifampicin in bodyweight-adjusted fixed-dose combination on days 1 to 7; on day 8, HAART including efavirenz 800 mg once daily was added. Blood samples were obtained on days 7 and 14. METHODS: Plasma concentrations of efavirenz and rifampicin were quantified by using validated high performance liquid chromatography assays, and pharmacokinetic parameter values were determined by noncompartmental methods. The differences between pharmacokinetic parameters on days 7 and 14 were used to assess interactions. RESULTS: There was a correlation between the pharmacokinetic parameters of efavirenz and the dose/kg administered. For efavirenz, mean (median) peak concentration, trough concentration and area under the concentration-time curve over the administration interval decreased 24% (24%), 25% (18%) and 22% (10%), respectively, in the presence of rifampicin. Large interpatient variability was observed, suggesting that plasma concentration monitoring of efavirenz may be advisable. Overall, the pharmacokinetics of efavirenz 800 mg plus rifampicin were similar to those of efavirenz 600 mg without rifampicin. The pharmacokinetics of rifampicin did not change substantially in the presence of efavirenz. Differences in patients' bodyweight appeared to cause further differences in exposure to efavirenz. Plasma concentrations of efavirenz in patients weighing <50 kg were similar to those previously described in HIV-infected patients without concomitant tuberculosis. However, plasma concentrations in patients weighing >or=50 kg were almost halved compared with those in patients weighing <50 kg. CONCLUSIONS: Although the minimal effective efavirenz plasma concentration that assures virological success is not currently known, it may be advisable to increase the dosage of efavirenz to 800 mg once daily when it is coadministered with rifampicin. Rifampicin can be used with efavirenz without dosage modification.     

Characterization and pharmacokinetic analysis of aerosolized aqueous voriconazole solution

Invasive fungal infections in immunocompromised patients have high mortality rates despite current treatment modalities. This study was designed to evaluate the suitability of an aqueous solution of voriconazole solubilized with sulfobutyl ether-β-cyclodextrin for targeted drug delivery to the lungs via nebulization. A solution was prepared such that the inspired aerosol dose was isotonic with an acceptable mass median aerodynamic diameter of 2.98 μm and a fine particle fraction of 71.7%. Following single and multiple inhaled doses, high voriconazole concentrations were observed within 30 min in the lung tissue and plasma. Drug solubilization with sulfobutyl ether-β-cyclodextrin contributed to the rapid and high drug concentrations in plasma following inhalation. Maximal concentrations in the lung and plasma were 11.0 ± 1.6 μg/g wet lung weight and 7.9 ± 0.68 μg/mL, respectively, following a single inhaled dose with a corresponding tissue/plasma concentration ratio of 1.4 to 1. Following multiple inhaled doses, peak concentrations in lung tissue and plasma were 6.73 ± 3.64 μg/g wet lung weight and 2.32 ± 1.52 μg/mL, respectively. AUC values in lung tissue and plasma were also high. The clinically relevant observed pharmacokinetic parameters of inhaled aqueous solutions of voriconazole suggest that therapeutic outcomes could be benefitted through the use of inhaled voriconazole.     

Differences in drug resistance profiles of Mycobacterium tuberculosis isolates causing pulmonary and extrapulmonary tuberculosis in a medical centre in Taiwan, 2000-2010

Few studies have investigated the drug resistance profiles of Mycobacterium tuberculosis (MTB) isolates recovered from different sites of infection. A total of 4521 non-duplicate MTB isolates, including 3723 (82.3%) from respiratory specimens and 798 (17.7%) from non-respiratory sources, were recovered from patients treated at a medical centre in Taiwan from 2000 to 2010. Trend analysis showed a significant decrease (P < 0.05) in the rates of resistance to isoniazid, rifampicin and ethambutol, a decrease in resistance to any one of four agents, namely isoniazid, rifampicin, ethambutol or streptomycin, and a decrease in resistance to both isoniazid and rifampicin (multidrug resistance) amongst pulmonary MTB isolates. A similar decrease in resistance to isoniazid and ethambutol was noted amongst non-pulmonary isolates. Rates of drug resistance were significantly higher amongst MTB isolates recovered from respiratory specimens than amongst those from non-respiratory specimens to 0.2 μg/mL isoniazid (15.3% vs. 9.4%; P < 0.0001), 1 μg/mL rifampicin (5.5% vs. 3.3%; P = 0.0108), 5 μg/mL ethambutol (7.3% vs. 3.8%; P = 0.0004), and both isoniazid and rifampicin (4.8% vs. 2.5%; P = 0.0051). Resistance rates amongst isolates causing tuberculous lymphadenitis were significantly lower than amongst those causing genitourinary tuberculosis (TB) to isoniazid (3.5% vs. 19.4%, P = 0.0012) and to isoniazid, rifampicin, ethambutol or streptomycin (9.6% vs. 22.6%, P = 0.0003). In conclusion, the rates of resistance to first-line anti-TB agents and to multiple agents differed amongst MTB isolates obtained from different infectious sources. Continuous monitoring of resistance of MTB isolates from various sites is necessary in order to establish an effective TB surveillance programme.     

Mono-hydroxy methoxychlor alters levels of key sex steroids and steroidogenic enzymes in cultured mouse antral follicles

Methoxychlor (MXC) is an organochlorine pesticide that reduces fertility in female rodents by decreasing antral follicle numbers and increasing follicular death. MXC is metabolized in the body to mono-hydroxy MXC (mono-OH). Little is known about the effects of mono-OH on the ovary. Thus, this work tested the hypothesis that mono-OH exposure decreases production of 17β-estradiol (E₂) by cultured mouse antral follicles. Antral follicles were isolated from CD-1 mice (age 35-39 days) and exposed to dimethylsulfoxide (DMSO), or mono-OH (0.1-10 μg/mL) for 96 h. Media and follicles were collected for analysis of sex steroid levels and mRNA expression, respectively. Mono-OH treatment (10 μg/mL) decreased E₂ (DMSO: 3009.72 ± 744.99 ng/mL; mono-OH 0.1 μg/mL: 1679.66 ± 461.99 ng/mL; 1 μg/mL: 1752.72 ± 532.41 ng/mL; 10 μg/mL: 45.89 ± 33.83 ng/mL), testosterone (DMSO: 15.43 ± 2.86 ng/mL; mono-OH 0.1 μg/mL: 17.17 ± 4.71 ng/mL; 1 μg/mL: 13.64 ± 3.53 ng/mL; 10 μg/mL: 1.29 ± 0.23 ng/mL), androstenedione (DMSO: 1.92 ± 0.34 ng/mL; mono-OH 0.1 μg/mL: 1.49 ± 0.43 ng/mL; 1 μg/mL: 0.64 ± 0.31 ng/mL; 10 μg/mL: 0.12 ± 0.06 ng/mL) and progesterone (DMSO: 24.11 ± 4.21 ng/mL; mono-OH 0.1 μg/mL: 26.77 ± 4.41 ng/mL; 1 μg/mL: 20.90 ± 3.75 ng/mL; 10 μg/mL: 9.44 ± 2.97 ng/mL) levels. Mono-OH did not alter expression of Star, Hsd3b1, Hsd17b1 and Cyp1b1, but it did reduce levels of Cyp11a1, Cyp17a1 and Cyp19a1 mRNA. Collectively, these data suggest that mono-OH significantly decreases levels of key sex steroid hormones and the expression of enzymes required for steroidogenesis.     

Evaluation of super-boosted lopinavir/ritonavir in combination with rifampicin in HIV-1-infected patients with tuberculosis

Rifampicin induces the metabolism of many drugs. To overcome the reduction in serum concentrations of lopinavir/ritonavir (LPV/r) when used in combination with rifampicin, 800/200 mg or 400/400 mg doses are used. This study evaluated super-boosted LPV/r (400/400 mg) in HIV/TB co-infected patients for adequate concentrations as well as short-term safety, tolerability and clinical response to therapy. This was an open-label, non-randomised pharmacokinetic (PK) study in HIV/TB patients. The primary objective was to determine the PK profile of super-boosted LPV/r when given with a rifampicin-based TB regimen. Secondary objectives were short-term safety, tolerability and clinical response. Primary endpoints were a lopinavir trough concentration (C_min) >1.0 µg/mL and a rifampicin maximum concentration (C_max) of 8–24 µg/mL. Secondary PK endpoints were a rifampicin area under the concentration–time curve from 0–24 h (AUC_0–24) of 44–70 µg·h/mL, a lopinavir C_max of 6–14 µg/mL and a lopinavir AUC_0–12 of 56–130 µg·h/mL. Eleven patients (10 male, age 25–43 years) were enrolled. Two patients were discontinued due to non-compliance. A lopinavir C_min of >1.0 µg/mL was achieved in a least one of the PK samplings in all nine subjects who completed treatment. All patients met lopinavir C_max and AUC_0–12 targets. Five patients achieved the primary endpoint of rifampicin C_max (≥8 µg/mL) in at least one of the PK samplings, and five achieved the minimum rifampicin AUC_0–24 (≥44 µg·h/mL). One grade 3 adverse event was reported. Super-boosted LPV/r was safe and effective in HIV/TB patients. [ClinicalTrials.gov ID NCT01700790.]     

Simultaneous quantification of daptomycin and rifampicin in plasma by ultra performance liquid chromatography: Application to a pharmacokinetic study

A rapid and simple method based on ultra performance liquid chromatography (UPLC) with ultra violet detection has been developed for the determination of daptomycin (DPT) and rifampicin (RFM) in rabbit plasma using 4-nitrophenol as internal standard (IS). Sample preparation involved protein precipitation with an acetonitrile:methanol mixture and centrifugation. Chromatographic separation was achieved on an Acquity BEH C18 column (100 mm × 2.1 mm, 1.7 μm) using gradient elution with methanol and 0.1% aqueous TFA. The total analysis time was 4.5 min with DPT and RFM eluting at 1.9 and 2.1 min, respectively. The method was fully validated with a lower limit of quantitation (LLOQ) of 2 μg mL⁻¹ for both DPT and RFM. The intra- and inter-day precision, measured as % relative standard deviation, were less than 12.1 for DPT and 10.7 for RFM, respectively. This validated method was successfully applied to a pharmacokinetic study involving intravenous administration of 14 mg kg⁻¹ DPT and 30 mg kg⁻¹ RFM to rabbits.     

Evaluation of cytotoxic,genotoxic and antigenotoxic potential of Solanum lycocarpum fruits glicoalkaloid extract in V79 cells

Solanum lycocarpum St.-Hil (Solanaceae) is a hairy shrub or small much-branched tree of the Brazilian Cerrado, popularly known as “fruit-of-wolf”. Considering that the induction of chromosomal mutations is involved in the process of carcinogenesis, and that S. lycocarpum is often used in folk medicine, it becomes relevant to study its effect on genetic material. In this sense, the aim of present study was to determine the possible cytotoxic, genotoxic and antigenotoxic potentials of S. lycocarpum fruits glycoalkaloid extract (SL) in Chinese hamster lung fibroblasts (V79 cells). The cytotoxicity was evaluated by the colony forming assay, apoptosis and necrosis assay, Trypan blue exclusion dye method and mitotic index. Genotoxic and antigenotoxic potential were evaluated by comet and chromosomal aberrations assays. Four concentrations of SL (4, 8, 16 and 32 μg/mL) were used for the evaluation of its genotoxic potential. The DNA damage-inducing agent methyl methanesulfonate (MMS, 22 μg/mL) was utilized in combination with extract to evaluate a possible protective effect. The results showed that SL was cytotoxic at concentrations above 32 μg/mL by the colony forming assay. For apoptosis and necrosis assay, the concentration of 64 μg/mL of SL showed statistically significant increase in cell death by apoptosis and necrosis, while the concentrations of 128 and 256 μg/mL of SL demonstrated statistically significant increase in cell death by necrosis, compared with the control group. Analysis of cell viability by Trypan blue exclusion indicated >96% viability for treatments with concentrations up to 32 μg/mL of SL. No significant differences in MI were observed between cultures treated with different concentrations of SL (4, 8, 16 and 32 μg/mL) alone or in combination with MMS and the negative control, indicating that these treatments were not cytotoxic. The comet and chromosomal aberrations assays revealed that SL does not display genotoxic activity. Moreover, the different concentrations of SL showed protective effect against both genomic and chromosomal damages induced by MMS.     

Investigating the enhancement of cisplatin cytotoxicity on 5637 cells by combination with mogoltacin

Transitional cell carcinomas (TCCs), which account for 90% of bladder cancers, arise from the transitional epithelium of bladder. Cisplatin is a chemotherapeutic drug used to treat bladder cancer, but intrinsic and acquired resistance to cisplatin limit its effectiveness. The aim of this study was to determine the ability of mogoltacin, a sesquiterpene-coumarin from Ferula badrakema, to enhance cytotoxic effects of cisplatin on 5637 cells, using MTT assay, comet method, DAPI staining and efflux assay.In order to analyse mogoltacin combinatorial effects, 5637 cells were cultured in the presence of various combined concentrations of mogoltacin and cisplatin. The results of MTT assay revealed that combination of 1 μg/mL cisplatin + 32 μg/mL mogoltacin, increased the cytotoxicity of cisplatin by 45.3%. Investigating the mechanism of this action by comet assay indicated that mogoltacin increases the apoptotic effects of cisplatin on 5637 cells via DNA lesion by 44%. Furthermore, studying nuclear morphological changes revealed that the combination of mogoltacin + cisplatin significantly (P < 0.001) increases the number of apoptotic cells. Results of efflux assay indicated that mogoltacin did not have any significant effect on the activity of MDR transporters, therefore, this sesquiterpene-coumarin increases the effects of cisplatin possibly by interacting with other drug transporters.     

Recreational exposure to microcystins during algal blooms in two California lakes

We conducted a study of recreational exposure to microcystins among 81 children and adults planning recreational activities on either of three California reservoirs, two with significant, ongoing blooms of toxin-producing cyanobacteria, including Microcystis aeruginosa (Bloom Lakes), and one without a toxin-producing algal bloom (Control Lake). We analyzed water samples for algal taxonomy, microcystin concentrations, and potential respiratory viruses (adenoviruses and enteroviruses). We measured microcystins in personal air samples, nasal swabs, and blood samples. We interviewed study participants for demographic and health symptoms information. We found highly variable microcystin concentrations in Bloom Lakes (<10 μg/L to >500 μg/L); microcystin was not detected in the Control Lake. We did not detect adenoviruses or enteroviruses in any of the lakes. Low microcystin concentrations were found in personal air samples (<0.1 ng/m³ [limit of detection]-2.89 ng/m³) and nasal swabs (<0.1 ng [limit of detection]-5 ng). Microcystin concentrations in the water-soluble fraction of all plasma samples were below the limit of detection (1.0 μg/L). Our findings indicate that recreational activities in water bodies that experience toxin-producing cyanobacterial blooms can generate aerosolized cyanotoxins, making inhalation a potential route of exposure. Future studies should include collecting nasal swabs to assess upper respiratory tract deposition of toxin-containing aerosols droplets.     

New HPLC assay for urinary salbutamol concentrations in samples collected post-inhalation

A new reversed phase high performance liquid chromatography (HPLC) method with florescence detection and two solid phase extraction (SPE) methods have been developed, optimised and validated for determining salbutamol in human urine after an inhalation. SPE methodology for unchanged salbutamol (USAL) and salbutamol plus its metabolites (USALMET) concentrations in urine has been developed using terbutaline as the internal standard. Confirm HCX cartridges were used for USAL and Oasis HLB for USALMET. Calibration lines of salbutamol urine standards were linear over the range 25–300 μg/L with mean (RSD) r² values of 0.9983 (0.06%) for USAL and 0.9976 (0.202%) for USALMET. The HPLC method was accurate (mean bias −0.40% for USAL and 0.46% for USALMET) and precise (mean RSD 5.0% for USAL and 2.90% for USALMET). The calculated LOD and LOQ for salbutamol using a 1 mL urine sample were 4.0 and 12.12 μg/L for USAL, and 4.80 and 14.56 μg/L for USALMET, respectively. The mean (RSD) SPE recoveries of salbutamol were 90.82% (2.32%) for USAL and 91.54% (2.96%) for USALMET. Both HPLC and SPE methods were applied to quantify unchanged and metabolised salbutamol excreted in urine after the inhalation of 200 μg salbutamol from metered dose inhalers (MDIs) by 14 healthy volunteers. Charcoal slurries were also ingested to prevent gastro-intestinal absorption. Urine samples were collected at 30 min post-inhalation and then pooled for the next 24 h. All urine concentrations were within the sensitive portion of the assay. The volunteer study revealed that following inhalation from an MDI about 20% of the nominal dose is deposited into the lungs and 46% is delivered to the systemic circulation. The results confirm the application, sensitivity, reliability and robustness of the HPLC and SPE methods for urinary pharmacokinetic studies after salbutamol inhalations using therapeutic doses.     

Interactions of silver nanoparticles with primary mouse fibroblasts and liver cells

Primary cells are ideal for in vitro toxicity studies since they closely resemble tissue environment. Here, we report a detailed study on the in vitro interactions of 7-20 nm spherical silver nanoparticles (SNP) with primary fibroblasts and primary liver cells isolated from Swiss albino mice. The intended use of silver nanoparticles is in the form of a topical antimicrobial gel formulation for the treatment of burns and wounds.Upon exposure to SNP for 24 h, morphology of primary fibroblasts and primary liver cells remained unaltered up to 25 μg/mL and 100 μg/mL SNP, respectively, although with minor decrease in confluence. IC₅₀ values for primary fibroblasts and primary liver cells as revealed by XTT assay were 61 μg/mL and 449 μg/mL, respectively. Ultra-thin sections of primary cells exposed to 1/2 IC₅₀ SNP for 24 h, visualized under Transmission electron microscope showed the presence of dark, electron dense, spherical aggregates inside the mitochondria, and cytoplasm, probably representing the intracellular SNP. When the cells were challenged with ∼ 1/2 IC₅₀ concentration of SNP (i.e. 30 μg/mL and 225 μg/mL for primary fibroblasts and primary liver cells, respectively), enhancement of GSH (∼ 1.2 fold) and depletion of lipid peroxidation (∼ 1.4 fold) were seen in primary fibroblasts which probably protect the cells from functional damage. In case of primary liver cells; increased levels of SOD (∼ 1.4 fold) and GSH (∼ 1.1 fold) as compared to unexposed cells were observed. Caspase-3 activity assay indicated that the SNP concentrations required for the onset of apoptosis were found to be much lower (3.12 μg/mL in primary fibroblasts, 12.5 μg/mL in primary liver cells) than the necrotic concentration (100 μg/mL in primary fibroblasts, 500 μg/mL in primary liver cells). These observations were confirmed by CLSM studies by exposure of cells to 1/2 IC₅₀ SNP (resulting in apoptosis) and 2× IC₅₀) cells (resulting in necrosis).These results clearly suggest that although silver nanoparticles seem to enter the eukaryotic cells, cellular antioxidant mechanisms protect the cells from possible oxidative damage. This property, in conjunction with the finding that primary cells possess much higher SNP tolerance than the concentration in the gel (∼ 20 μg/g), indicates preliminary safety of the formulation and warrants further study for possible human application.     

Phenolic composition and biological activities of Juniperus drupacea Labill. berries from Turkey

The present study was designed to define the phenolic profile and the biological potential of berries methanol extract of Juniperus drupacea Labill. from Turkey.The total phenolic content (Folin-Ciocalteau assay) was 48.06 ± 0.99 mg GAE/g extract. The HPLC-DAD-ESI-MS analysis allowed the determination of the complete phenolic profile of J. drupacea berries. Phenolic acids represented more than 60% of the total phenolics, and tyrosol was the major one (1324 ± 0.64 μg/g extract); within the flavonoids amentoflavone was detected as the main constituent (927 ± 0.35 μg/g extract).The extract exhibited good antioxidant properties, as determined by different in vitro models: DPPH test (IC₅₀ 0.38 ± 0.02 mg/mL), reducing power (12.63 ± 0.14 ASE/mL), Fe²⁺ chelating ability (IC₅₀ 2.26 ± 0.06 mg/mL), and TBA test (IC₅₀ 2.47 ± 1.13 μg/mL).Cytotoxicity against Artemia salina was highlighted (LC₅₀ 489.47 ± 27.8 μg/mL), and a significant decrease (p ? 0.05; p ? 0.01) in HepG2 cells viability was observed at the higher concentrations (5-10 μg/mL).The extract displayed good antibacterial activity towards Gram-positive bacteria and in particular Staphylococcus aureus was the most susceptible strain (MIC 78.12 μg/mL).     

Selection of an analytical method for evaluating bovine serum albumin concentrations in pharmaceutical polymeric formulations

Bovine serum albumin (BSA) is a commonly used model protein in the development of pharmaceutical formulations. In order to assay its release from various dosage forms, either the bicinchoninic acid (BCA) assay or a more specific size-exclusion high performance liquid chromatography (SE-HPLC) method are commonly employed. However, these can give erroneous results in the presence of some commonly used pharmaceutical excipients. We therefore investigated the ability of these methods to accurately determine BSA concentrations in pharmaceutical formulations that also contained various polymers and compared them with a new reverse-phase (RP)-HPLC technique. We found that the RP-HPLC technique was the most suitable method. It gave a linear response in the range of 0.5–100 μg/ml with a correlation co-efficient of 0.9999, a limit of detection of 0.11 μg/ml and quantification of 0.33 μg/ml. The performed ‘t’-test for the estimated and theoretical concentrations indicated no significant difference between them providing the accuracy. Low % relative standard deviation values (0.8–1.39%) indicate the precision of the method. Furthermore, the method was used to quantify in vitro BSA release from polymeric freeze-dried formulations.     

Determination of voriconazole in human serum and plasma by micellar electrokinetic chromatography

The micellar electrokinetic capillary chromatography (MEKC) separation and analysis of voriconazole and UK 115794 (internal standard) were examined and an assay for determination of voriconazole in human plasma and serum was developed. The MEKC medium comprises a 2:15 (v/v) mixture of methanol and a pH 9.3 buffer composed of 5 mM Na₂B₄O₇, 7 mM Na₂HPO₄ and 54 mM SDS. Sample preparation is based upon liquid/liquid extraction with ethylacetate and dichloromethane (75%/25%) at physiological pH. Using this approach with 250 μl serum or plasma and reconstitution of the dried extract into 100 μl of a buffer composed of 0.5 mM Na₂B₄O₇ and 0.7 mM Na₂HPO₄ (pH 9.3), the detection and quantitation limits were determined to be 0.1 and 0.2 μg/ml, respectively, a sensitivity that is suitable for therapeutic drug monitoring of voriconazole (provisional therapeutic range: 1–6 μg/ml) in human plasma and serum samples. The method was validated and compared to an HPLC method, showing excellent agreement between the two for a set of 91 samples that stemmed from patients being treated with voriconazole. The MEKC assay is also demonstrated to be suitable to explore pharmacokinetic data of voriconazole.     

High performance liquid chromatography-diode array and electrospray-mass spectrometry analysis of vardenafil,sildenafil, tadalafil,testosterone and local anesthetics in cosmetic creams sold on the Internet web sites

A simple high-performance liquid chromatography (HPLC) method with ultraviolet diode array (UV-DAD) and electrospray ionisation mass spectrometry (ESI-MS) detection has been developed for the determination of vardenafil, sildenafil, tadalafil, testosterone, procaine, lidocaine, prilocaine, and benzocaine in cosmetic creams sold as promising remedies for male erectile dysfunction and female genitals stimulation. The presence of these substances in commercial cosmetic samples is prohibited. Aliquots (1 g) of the cosmetic creams under investigation were diluted 1:100 in methanol, subjected to ultrasonic treatment, added with benzoic acid as internal standard, and analyzed by HPLC–DAD and HPLC–ESI-MS after a further 1:1000 dilution. The compounds were separated by reversed phase chromatography with water (0.02% trifluoroacetic acid) and acetonitrile gradient elution and detected by UV-DAD at 228, 255 and 290 nm and by ESI-MS positive ionisation mode. Benzoic acid was used as internal standard. Linearity was studied with UV-DAD detection from 2.5–7.8 to 250 μg/g range, depending on the different compounds and with ESI-MS in the 3.3–8.9 to 250 ng/g range. Good determination coefficients (r² ≥ 0.99) were found in both UV-DAD and ESI-MS. Limits of quantifications ranged between 2.5 and 7.8 μg/g for HPLC–UV-DAD assay and between 3.3 and 8.9 ng/g for HPLC–ESI-MS assay depending on different analyzed substances. At three concentrations spanning the linear dynamic ranges of both UV-DAD and ESI-MS assay, mean recoveries were always higher than 90% for the different analytes and intra-assay and inter-assay precision always better than 15% and 12%. This method was successfully applied to the analysis of substances under investigations present in cosmetic creams, freely sold on the Internet web-sites.     

Validation of a Drug-Resistant Anti-Adalimumab Antibody Assay to Monitor Immunogenicity in the Presence of High Concentrations of Adalimumab

With respect to patient safety and long-term efficacy, immunogenicity of therapeutic antibodies remains an important issue. Pre-treatment of samples using either higher temperature or acidification in order to separate drug/anti-drug antibody complexes has been implemented in the traditional bridging assay and an in-house-developed affinity capture elution assay but only a limited drug tolerance was obtained. In this study, we aim to apply a drug-resistant anti-drug antibody assay to adalimumab through a combination of adalimumab/anti-adalimumab antibody complex precipitation and acid dissociation. A linear dose–response curve ranging from 3.1 to 200 ng/mL was obtained in 1/125 diluted serum, allowing detection of anti-adalimumab antibody concentrations up to 25 μg/mL equivalents MA-ADM6A10, a calibrator anti-adalimumab antibody. The cut-off point for detection was determined using 16 samples of adalimumab naïve patients and set at 0.39 μg/mL equivalents. Validation of the assay revealed that no detectable anti-adalimumab antibody concentrations were found in samples with either a positive anti-infliximab antibody concentration, a physiologic concentration of TNFα, or a high concentration of rheumatoid factor. Full recoveries were obtained when various concentrations of adalimumab (0, 1, 10, and 50 μg/mL) were spiked to 1, 2, and 4 μg/mL of MA-ADM6A10. Spiking of 50 μg/mL adalimumab to eight individual sera revealed similar anti-adalimumab antibody concentrations as in the absence of adalimumab, with a Pearson r correlation of 0.99 and an interclass correlation of 0.99. The assay allows accurate evaluation of adalimumab immunogenicity during induction or upon dose intensification and in serum samples not taken at trough.     

Liquid chromatographic determination of lumiracoxib in pharmaceutical formulations

A stability-indicating reversed-phase liquid chromatography (LC) method was developed and validated for the determination of lumiracoxib in pharmaceutical formulations. The LC method was carried out on a Synergi fusion C₁₈ column (150 mm × 4.6 mm), maintained at 30 °C. The mobile phase was composed of phosphoric acid (25 mM; pH 3.0)/acetonitrile (40:60, v/v), run at a flow rate of 1.0 mL/min, and detection at 272 nm. The chromatographic separation was obtained within 10 min and it was linear in the concentration range of 10–100 μg/mL (r² = 0.9999). Validation parameters such as the specificity, linearity, precision, accuracy, and robustness were evaluated, giving results within the acceptable range. Stress studies were carried out and no interference of the degradation products was detected. Moreover, the proposed method was successfully applied for the assay of lumiracoxib in pharmaceutical formulations.