Sensitive "release-on-demand" fluorescent genosensors for probing DNA damage induced by commonly used cardiovascular drugs: Comparative study.

Cardiovascular drugs (CVDs) are agents working on the heart and the vascular system to treat many cardiovascular disorders. Such disorders represent the leading cause for morbidity and mortality worldwide. The treatment regimen includes different administered drugs on chronic basis. The cumulative drugs in human body coincides with exposure to electromagnetic radiations from different sources leading to drug-radiation interaction that may lead to drug photosensitization. Such photosensitization may lead to mutagenesis, cancer, and cell death due to molecular damage to DNA. This work involves the application of two bioluminescent genosensors; Terbium chloride and EvaGreen are utilized to investigate potential DNA damage caused by frequently used CVDs following UVA irradiation. A variety of CVDs are investigated. Ten drugs; Amiloride, Atorvastatin, Captopril, Enalapril, Felodipine, Hydrochlorothiazide, Indapamide, Losartan, Triamterene and Valsartan are studied. The study's findings showed that such drugs induced DNA damage following UVA irradiation. The induced DNA damage altered the fluorescence of terbium chloride and EvaGreen genosensors, proportionally. The results are confirmed by viscosity measurements reflecting the possible intercalation of CVDs with DNA. Also, the work is applied on calf thymus DNA to mimic the actual biological variability. The demonstrated bioluminescent genosensors provide automatic, simple and low-cost methods for assessing DNA-drug interactions.

Pharmacokinetic interaction between linagliptin and tadalafil in healthy Egyptian males using a novel LC-MS method.

Aim: Assessment of pharmacokinetic interaction between linagliptin (LNG) and tadalafil (TDL) in healthy males. Methods: First, a novel LC-MS method was developed; second, a Phase IV, open-label, cross-over study was performed. Volunteers took single 20-mg TDL dose on day 1 followed by wash out period of 2 weeks then multiple oral dosing of 5-mg/day LNG for 13 days. On day 13, volunteers were co-administered 20-mg TDL. Results: LNG and TDL single doses did not affect QTc interval. Smoking did not alter pharmacokinetics/pharmacodynamics of LNG and TDL. Co-administration of LNG with TDL resulted in TDL longer time to reach maximum plasma concentration (Tmax), decreased oral clearance (Cl/F) and oral volume of distribution (Vd/F), increased its maximum plasma concentration (Cmax), area under concentration-time curve (AUC), muscle pain and QTc prolongation. Conclusion: LNG and TDL co-administration warrants monitoring and/or TDL dose adjustment.

Chromatographic determination of zonisamide, topiramate and sulpiride in plasma by a fluorescent 'turn-on' chemosensor.

AIM: Antiepileptics (AEDs) and antipsychotics are often coprescribed. Interactions between these drugs may affect both efficacy and toxicity. Therefore, drug monitoring is necessary for appropriate dosage adjustments. MATERIALS & METHODS: Specific 'turn-on' chemosensor, 4-chloro-7-nitrobenzofurazan is used for selective and sensitive determination of two AEDs: zonisamide (ZON) and topiramate (TOP) with the antipsychotic sulpiride (SUL) in epileptic patients' plasma followed by reversed-phase-HPLC separation without any interference. RESULTS: Linear behavior was observed in the range of 0.1-3 µg/ml and 0.01-0.5 µg/ml for the AEDs and SUL, respectively, with LOD of 33, 46 and 4 ng/ml and LOQ of 86, 93 and 9 ng/ml for ZON, TOP and SUL, respectively. The proposed method was successfully applied for determination of different pharmacokinetic parameters of ZON and TOP, and for clinical monitoring of the three drugs in healthy volunteers following oral administration. CONCLUSION: The developed method is suitable for the routine therapeutic drug monitoring of these drugs.

Sensitive inexpensive HPLC determination of four antiepileptic drugs in human plasma: application to PK studies.

AIM: Recently, polytherapy regimen has been introduced for the treatment of epileptic patients for better seizure control with lesser side effects and better control of multiple seizure types. METHODOLOGY: A simple, sensitive and highly specific reversed-phase HPLC method was developed for simultaneous determination of four antiepileptic drugs (AEDs), levetiracetam, lamotrigine, oxcarbazepine and carbamazepine, in real human plasma without interference from endogenous components of plasma. CONCLUSION: The method was proved to be linear in the range of 0.5-50 µg/ml for all drugs. It was successfully applied for clinical PK study of the AEDs in healthy volunteers following single administration. Also, this method was applied for simultaneous determination of the studied drugs in volunteers' plasma receiving synergistic binary combinations from the four AEDs when used as add-on therapy. The good precision and selectivity of the developed method allow it to be used for routine therapeutic drug monitoring of such drugs as a useful tool in epilepsy management.

Stability-Indicating HPLC-DAD Method for the Determination of Linagliptin in Tablet Dosage Form: Application to Degradation Kinetics.

This work aims to develop HPLC-DAD method for linagliptin (LNG) quantitation in the presence of its degradation products in tablets and to study its degradation kinetics. LNG samples were extracted from tablets and diluted. Various ICH degradation conditions were applied to study LNG degradation kinetics. LNG was assayed by a C18 column using a simple isocratic mobile phase (methanol:water containing 0.3% TEA, 40:60, pH 4.5) pumped at 1 mL/min. The drug was detected at 225 nm. The method showed high linearity (r2 > 0.999) with CV% and % error of the mean <2% over the range of 1-50 µg/mL. Limits of detection and quantitation were 0.3 and 1.0 µg/mL, respectively. LNG retention time was 11 min with a total run time of 17 min. In all degradation conditions applied, LNG was well separated from its degradation products. The method was successfully used to quantitate LNG content in its tablets and study its degradation kinetics in acidic, alkaline and oxidative forced degradation experiments. In conclusion, simple, precise and reliable method for the separation and determination of LNG in the presence of its degradation products under different stress conditions was developed and validated according to the latest ICH guidelines.

HPTLC Determination of Three Gliptins in Binary Mixtures with Metformin.

A single, simple, selective and validated high performance thin layer chromatographic (HPTLC) method was developed for the determination of either linagliptin (LGP), saxagliptin (SGP) or vildagliptin (VGP) in their binary mixtures with metformin (MET) in pharmaceutical preparations using environmentally preferable green mobile phase system. Separation was carried out on Merck HPTLC aluminum sheets of silica gel 60 F254 using methanol-0.5% w/v aqueous ammonium sulfate (8 : 2, v/v) as mobile phase. Densitometric measurement of the spots was performed at 225 nm for LGP/MET mixture and at 208 nm for both SGP/MET and VGP/MET mixtures. The linear regression analysis data were used for the regression line in the range of 0.05-0.5 µg/band for LGP and SGP and 0.2-2 and 5-40 µg/band for VGP and MET, respectively. The method was validated and showed good performances in terms of linearity, limits of detection and quantitation, precision, accuracy, selectivity and specificity. The calculated percentage relative error values and percentage relative standard deviation for intra- and interday precision studies did not exceed 2%. The developed method was satisfactorily applied for the analysis of pharmaceutical preparations and proved to be specific and accurate for the quality control of the cited drugs in their dosage forms.

Bioavailability study of triamterene and xipamide using urinary pharmacokinetic data following single oral dose of each drug or their combination.

An efficient chromatographic method for the simultaneous determination of triamterene (TRI) and xipamide (XIP) in urine samples, based on high performance liquid chromatography with photodiode array detector (HPLC-DAD) has been developed. The HPLC separation was performed on a RP stainless-steel C-18 analytical column (250 mm × 4.6 mm, 5 µm) with a gradient elution system of 0.05 M phosphate buffer adjusted to pH 4.0 and methanol as the mobile phase. The method was used to determine the urinary excretion profile and to calculate different urinary pharmacokinetic parameters following oral dose of their combination compared with single oral doses of each drug and hence comparing their bioavailability. Quantitation was performed using chlorthalidone as internal standard. The calibration graphs of each drug were rectilinear in the range of 0.2-40 µg/mL urine for TRI and 0.2-15 µg/mL urine for XIP. An HPLC-DAD method was also successfully developed for the simultaneous determination of the investigated drugs in pharmaceutical preparations. The methods were validated in terms of linearity, accuracy, precision, selectivity, limits of detection and quantitation and other aspects of analytical validation.

Enhanced spectrophotometric determination of two antihyperlipidemic mixtures containing ezetimibe in pharmaceutical preparations.

Two spectrophotometric methods are presented for the simultaneous determination of ezetimibe/simvastatin and ezetimibe/atorvastatin binary mixtures in combined pharmaceutical dosage forms without prior separation. The first is the derivative ratio method where the amplitudes of the first derivative of the ratio spectra ((1) DD) at 299.5 and 242.5 nm were found to be linear with ezetimibe and simvastatin concentrations in the ranges 0.5-20 µgml(-1) and 1-40 µgml(-1) , respectively, whereas the amplitudes of the first derivative of the ratio spectra ((1) DD) at 289.5 and 288 nm were selected to determine ezetimibe and atorvastatin in the concentration ranges 5-50 µgml(-1) and 1-40 µgml(-1) , respectively. The second is the H-point standard additions method; absorbances at the two pairs of wavelengths, 228 and 242 nm or 238 and 248 nm, were monitored while adding standard solutions of ezetimibe or simvastatin, respectively. For the analysis of ezetimibe/atorvastatin mixture, absorbance values at 226 and 248 nm or 212 and 272 nm were monitored while adding standard solutions of ezetimibe or atorvastatin, respectively. Moreover, differential spectrophotometry was applied for the determination of ezetimibe in the two mixtures without any interference from the co-existing drug. This was performed by measurement of the difference absorptivities (ΔA) of ezetimibe in 0.07 M 30% methanolic NaOH relative to that of an equimolar solution in 0.07 M 30% methanolic HCl at 246 nm. The described methods are simple, rapid, precise and accurate for the determination of these combinations in synthetic mixtures and dosage forms.

Development of a differential pulse voltammetric method for the determination of Silymarin/Vitamin E acetate mixture in pharmaceuticals.

Differential pulse voltammetric method was developed for determination of Silymarin (SMR)/Vitamin E acetate (VEA) mixture in pharmaceuticals. SMR and VE gave well-resolved diffusion-controlled anodic peaks at +756 and +444mV, respectively (versus Ag/AgCl) in Britton-Robinson buffer at pH 2.8. The solution conditions and instrumental parameters were optimized for their quantitative determination. The linear response was obtained in the range 0.1-4.0mgL(-1) with a detection limit of 0.03mgL(-1) for SMR and 0.05-4.0mgL(-1) with a detection limit of 0.01mgL(-1)for VEA.