Simultaneous determination of nitrendipine and hydrochlorothiazide in spontaneously hypertensive rat plasma using HPLC with on-line solid-phase extraction

Benzaldehyde, A New Absorption Promoter, Accelerating Absorption on Low Bioavailability Drugs Through Membrane Permeability

Styrax, one of the most famous folk medicines, is a necessary medicine in formulas to help other drugs reach the focal zone and maximize the effectiveness, the mechanism that promotes absorption is not clear yet. This study was carried out to investigate the absorption-promoting effects and the mechanism of benzaldehyde, a key active compound of styrax, on the diffusion rates of drugs with different oral bioavailability. Caco-2 transport experiments were used to investigate the transport rate. Molecular Dynamics Simulation analysis and fluorescence-anisotropy measurements were used to explore the underlying mechanism of absorption-promoting. Validation test in vivo was carried out to reveal the absorption-promoting effects of benzaldehyde on high hydrophilicity drugs. Our data indicated that benzaldehyde(50 μM) elevated the cumulative quantity of passively diffusion drugs with high hydrophilicity such as acyclovir and hydrochlorothiazide. MD and membrane fluidity data explained that benzaldehyde can loosen the structure of the lipid bilayer. The validation tests showed that benzaldehyde (140 mg/kg) remarkably increased the C_max and AUC0-6 of acyclovir and hydrochlorothiazide in vivo. These present studies suggested that benzaldehyde can promote the absorption of drugs with a lower oral bioavailability through disturbing the integrity of lipid bilayer enhanced membrane permeability.

Validated LC-MS/MS method for the simultaneous determination of enalapril maleate, nitrendipine, hydrochlorothiazide, and their major metabolites in human plasma

Hypertension is a major risk factor for atherosclerosis and ischemic heart disease. Most hypertensive patients need a combination of antihypertensive agents to achieve therapeutic goals. A rapid, sensitive, and selective liquid chromatography-tandem mass spectrometric method was developed and validated for simultaneous determination of enalapril maleate (ENA) and its major metabolite enalaprilat (ENAT), nitrendipine (NIT) and its major metabolite dehydronitrendipine (DNIT), and hydrochlorothiazide (HCT) in human plasma using felodipine as an internal standard (IS). The drugs were extracted from plasma using one-step protein precipitation. Chromatographic separation was performed on a Symmetry C₁₈ column, with water and acetonitrile (10:90, v/v) as mobile phase. The detection was carried out using multiple reaction monitoring mode and coupled with electrospray ionization source. Multiple reaction monitoring transitions were m/z 377.1 → 234.1 for ENA, m/z 349.2 → 206.1 for ENAT, m/z 361.2 → 315.1 for NIT, m/z 359 → 331 for DNIT, m/z 295.9 → 205.1 for HCT, and m/z 384.1 → 338 for felodipine (IS). The method was linear over concentration ranges of 1-200, 20-500, 5-200, 2-100, and 5-200 ng/mL for ENA, ENAT, NIT, DNIT, and HCT, respectively, with r² ≥ 0.99. Method validation was performed according to U.S. Food and Drug Administration guidelines. The validated method showed good sensitivity and selectivity and could be applied for therapeutic drug monitoring and bioequivalence studies.

Development and optimization of nanoemulsion based gel for enhanced transdermal delivery of nitrendipine using box-behnken statistical design

Objective: The purpose of present research was to develop and statistically optimize nitrendipine nanoemulsion gel for transdermal delivery using box-behnken statistical design.Method: The nanoemulsion formulations bearing nitrendipine were prepared by application of ternary phase diagram and spontaneous emulsification method. Box-behnken design was employed for the optimization of nitrendipine loaded nanoemulsion. The independent variables were oil, surfactant and co-surfactant while globule size, drug content and zeta potential were dependent variables. The optimized nanoemulsion formulation was incorporated into gel and evaluated for in-vitro release, ex-vivo permeation studies, confocal laser scanning microscopy, skin irritation and histopathological studies.Results: The optimized formulation through box-behnken statistical design showed globule size of 20.43 ± 1.50 nm, drug content of 97.05 ± 1.77% and zeta potential of -15.45 ± 0.35 mV. The ex-vivo study confirmed the enhanced delivery of nitrendipine from nanoemulsion gel than compare to drug solution by virtue of better permeation and solubility. Nanoemulsion gel was proved significantly superior by confocal laser scanning microscopy for satisfactory permeation and distribution of gel, deep into the rat skin. The optimized gel was found with no allergic dermal effects and was proved safe by histopathological studies for transdermal application.Conclusions: Results reveals that developed nitrendipine nanoemulsion gel overcomes the limitation of low penetration and accentuate permeation through albino Wistar rat skin. It was concluded that nanoemulsion gel could be utilized as a potential carrier for transdermal delivery of nitrendipine.

Vanillin enhances the passive transport rate and absorption of drugs with moderate oral bioavailability in vitro and in vivo by affecting the membrane structure

Vanillin is a popular flavoring agent in the food, tobacco, and perfume industries.

Stability of 5 mg/mL Nitrendipine Oral Suspension in Syrspend® SF PH4

Background

Nitrendipine is prescribed to children for the treatment of primary hypertension (off-label use). Available specialties (Nidrel®, Baypress® and others generic drugs) are only marketed in tablet form, which is unsuitable for pediatric use. A hospital preparation of nitrendipine oral suspension at 5 mg/mL was developed. The aim of the study was to determine physicochemical and microbiological stability of the nitrendipine oral suspension in order to set a shelf life for the preparation.

Methods

A validated high-performance liquid chromatographic (HPLC) method was developed for the assay of nitrendipine. Nitrendipine oral suspensions were prepared using 20 mg Nidrel® tablets and suspending vehicle Syrspend® SF PH4. These preparations were packaged in amber glass bottles and stored at room temperature. The physicochemical (pH, osmolality, nitrendipine concentration, macroscopic changes) and microbiological stability of the preparation was tested over 90 days. Nitrendipine concentration at day 0 was considered as 100 % and nitrendipine concentration in subsequent samples greater than 95 % were considered stable.

Results

The developed HPLC method was validated in terms of linearity, accuracy, precision and specificity. After 90 days, no significant pH and osmolality variation was observed. No microbial growth was noted. Concentrations of nitrendipine were found to be always higher 95 % of the initial concentration.

Conclusions

Nitrendipine oral suspensions 5 mg/mL are stable for at least 90 days when stored at temperature room and in amber glass bottles. This suspension is more suitable for children than tablets and allows obtaining accurate doses based on patient’s body weight.

Enhanced absorption and bioavailability of hydrochlorothiazide by Chinese medicines in the Zhenju antihypertensive compound

OBJECTIVES

This study was performed to investigate the influence of traditional Chinese medicines in the Zhenju antihypertensive compound (ZJAHC) on the oral absorption of hydrochlorothiazide (HCT) both in vitro and in vivo.

METHODS

Caco-2 cells and the in situ closed loop system were used to investigate the possible mechanism of the Chinese-Western medicine interaction on the transepithelial transport and uptake of HCT. The influence of TCMs on the pharmacokinetics and bioavailability of HCT was also studied to reveal the possible interaction in vivo.

KEY FINDINGS

In an in situ intestinal perfusion study, the cumulative amount of HCT of ZJAHC group (506.05 μg ± 96.03) was 2.2-fold, 2.18-fold and 1.38-fold higher compared to that of the HCT group (228.29 μg ± 23.39), HCT-clonidine (CLO) group (232.13 ± 54.79 μg) and HCT-rutin (RT) group (366.08 ± 21.97 μg), respectively, after 120 min of perfusion. A pharmacokinetic analysis showed a significant increase in area under the plasma concentration-time curve (AUC) of HCT in the ZJAHC group by 2.14-fold, 2.01-fold and 1.32-fold compared to the HCT, HCT-CLO and HCT-RT groups, respectively. As a P-gp inhibitor, RT could contribute to the enhanced oral absorption of HCT in ZJAHC.

CONCLUSION

The combination of traditional Chinese medicines and chemical drugs may provide a promising strategy and unique advantages to reduce the dosage and side effects of chemical drugs while maintaining an effect on hypertension.