A Novel Ambroxol-Derived Tetrahydroquinazoline with a Potency against SARS-CoV-2 Proteins.

We report synthesis of a novel 1,2,3,4-tetrahydroquinazoline derivative, named 2-(6,8-dibromo-3-(4-hydroxycyclohexyl)-1,2,3,4-tetrahydroquinazolin-2-yl)phenol (1), which was obtained from the hydrochloride of 4-((2-amino-3,5-dibromobenzyl)amino)cyclohexan-1-ol (ambroxol hydrochloride) and salicylaldehyde in EtOH. The resulting compound was produced in the form of colorless crystals of the composition 1∙0.5EtOH. The formation of the single product was confirmed by the IR and 1H spectroscopy, single-crystal and powder X-ray diffraction, and elemental analysis. The molecule of 1 contains a chiral tertiary carbon of the 1,2,3,4-tetrahydropyrimidine fragment and the crystal structure of 1∙0.5EtOH is a racemate. Optical properties of 1∙0.5EtOH were revealed by UV-vis spectroscopy in MeOH and it was established that the compound absorbs exclusively in the UV region up to about 350 nm. 1∙0.5EtOH in MeOH exhibits dual emission and the emission spectra contains bands at about 340 and 446 nm upon excitation at 300 and 360 nm, respectively. The DFT calculations were performed to verify the structure as well as electronic and optical properties of 1. ADMET properties of the R-isomer of 1 were evaluated using the SwissADME, BOILED-Egg, and ProTox-II tools. As evidenced from the blue dot position in the BOILED-Egg plot, both human blood-brain barrier penetration and gastrointestinal absorption properties are positive with the positive PGP effect on the molecule. Molecular docking was applied to examine the influence of the structures of both R-isomer and S-isomer of 1 on a series of the SARS-CoV-2 proteins. According to the docking analysis results, both isomers of 1 were found to be active against all the applied SARS-CoV-2 proteins with the best binding affinities with Papain-like protease (PLpro) and nonstructural protein 3 (Nsp3_range 207-379-AMP). Ligand efficiency scores for both isomers of 1 inside the binding sites of the applied proteins were also revealed and compared with the initial ligands. Molecular dynamics simulations were also applied to evaluate the stability of complexes of both isomers with Papain-like protease (PLpro) and nonstructural protein 3 (Nsp3_range 207-379-AMP). The complex of the S-isomer with Papain-like protease (PLpro) was found to be highly unstable, while the other complexes are stable.

Development and characterization of novel ambroxol sustained-release oral suspensions based on drug-polymeric complexation and polymeric raft formation.

The aim was to develop sustained-release aqueous suspensions of ambroxol utilizing drug-polymer complexation and raft-forming formulations. Ambroxol-carrageenan (ABX-CRG) complexation was studied for the optimum binding capacity, which was used to prepare the complex by kneading and coprecipitation. The prepared complex was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry and powder X-ray diffractometry. The complex was formulated as suspensions in aqueous raft-forming vehicle of sodium alginate (NA) and calcium carbonate (CC). The suspensions differed in the molecular weight and concentration of NA, in addition to CC level and inclusion of CRG in excess of drug-polymer complexation. In 0.1 M HCl as simulated gastric fluid, the suspensions were observed for their ability to form rafts and studied for drug-release. The optimum sustained-release, raft forming and pourable formulation using high molecular weight NA, NA concentration of 18 mg/ml and CC concentration of 9 mg/ml was reached. Another optimum suspension was obtained by replacement of CC with excess CRG. However, pH dissolution profiles of the optimum suspensions revealed less pH sensitivity of the release consequent to this replacement as well as more stable ABX release upon aging. Relative to Gaviscon liquid, the optimum suspensions formed rafts of similar strength and higher resilience.

Exploring the Potential of Hydrophilic Matrix Combined with Insoluble Film Coating: Preparation and Evaluation of Ambroxol Hydrochloride Extended Release Tablets.

To explore the potential utility of combination of hydrophilic matrix with membrane-controlled technology, the present study prepared tablets of a water-soluble model drug (ambroxol hydrochloride), through process of direct compression and spray coating. Single-factor experiments were accomplished to optimize the formulation. In vivo pharmacokinetics was then performed to evaluate the necessity and feasibility of further development of this simple process and low-cost approach. Various release rates could be easily obtained by adjusting the viscosity and amount of hypromellose, pore-former ratios in coating dispersions and coating weight gains. Dissolution profiles of coated tablets displayed initial delay, followed by near zero-order kinetics. The pharmacokinetic study of different formulations showed that lag time became longer as the permeability of coating membrane decreased, which was consistent with the in vitro drug release trend. Besides, in vitro/in vivo correlation study indicated that coated tablets exhibited a good correlation between in vitro release and in vivo absorption. The results, therefore, demonstrated that barrier-membrane-coated matrix formulations were extremely promising for further application in industrialization and commercialization.

Simultaneous bioanalysis and pharmacokinetic interaction study of acebrophylline, levocetirizine and pranlukast in Sprague-Dawley rats.

The combination of acebrophylline (ABP), levocetirizine (LCZ) and pranlukast (PRN) is used to treat allergic rhinitis, asthma, hay-fever and other conditions where patients experience difficulty in breathing. This study was carried out with the aim of developing and validating a reverse-phase high-performance liquid chromatographic bioanalytical method to simultaneously quantitate ABP, LCZ and PRN in rat plasma. The objective also includes determination of the pharmacokinetic interaction of these three drugs after administration via the oral route after individual and combination treatment in rat. Optimum resolution between the analytes was observed with a C18 Kinetex column (250 mm × 4.6 mm × 5 µm). The chromatography was performed in a gradient elution mode with a 1 mL/min flow rate. The calibration curves were linear over the concentration range of 100-1600 ng/mL. The intra- and inter-day precision and accuracy were found to be within acceptable limits as specified in US Food and Drug Administration guideline for bioanalytical method validation. The analytes were stable on the bench-top (8 h), after three freeze-thaw cycles, in the autosampler (8 h) and as a dry extract (-80°C for 48 h). The statistical results of the pharmacokinetic study in Sprague-Dawley rats showed a significant change in pharmacokinetic parameters for PRN upon co-administration of the three drugs.

Pharmacokinetics and safety of salbutamol/ambroxol fixed-dose combination granules in healthy Chinese subjects
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OBJECTIVES: The aim of the study was to investigate the pharmacokinetics and tolerability of salbutamol/ambroxol fixed-dose combination granules following single and multiple dosing in healthy Chinese subjects. MATERIALS AND METHODS: This was a randomized, open-label, two-period, one-sequence study (n = 12). Each subject received a single oral dose in period 1 and multiple doses in period 2. Plasma concentrations of these two components were determined using a validated LC-MS/MS method. Adverse events (AEs) were documented throughout the study. Investigators evaluated AEs in terms of frequency, duration, intensity, seriousness, outcome, and relationship to study drugs. RESULTS: Following single dosing, Cmax values were 8.07 ± 1.31 ng/mL and 25.7 ± 6.5 ng/mL for salbutamol and ambroxol, respectively. The corresponding T1/2 values were 8.15 ± 3.13 hours and 9.31 ± 2.27 hours, respectively. Moreover, no statistical differences in the pharmacokinetics of salbutamol and ambroxol in subjects receiving single or multiple dosage were observed. Single- and multiple-dose oral administration of fixed-dose combination granules were safe and well tolerated in healthy Chinese subjects. Drug hypersensitivity syndrome did not occur during our study. CONCLUSION: The pharmacokinetics of salbutamol and ambroxol in the fixed-dose combination granules were not affected by dosing duration, and gender differences seemed to have no effect on the pharmacokinetics of salbutamol and ambroxol after a single dose and multiple doses of the medication.
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Investigation of a potential drug-drug interaction between salbutamol and ambroxol and bioequivalence of a new fixed-dose combination containing these two drugs in healthy Chinese subjects.

OBJECTIVES: The aims of the study were to investigate the potential drug-drug interaction between salbutamol and ambroxol, the bioequivalence of the new fixed-dose combination containing salbutamol and ambroxol compared with co-administration of the two separate formulations, and to describe the safety and tolerability of the fixed-dose combination formulation in healthy Chinese volunteers. MATERIALS AND METHODS: An open-label, single-dose, four-treatment, four-period crossover study for evaluation of drug-drug interaction and bioequivalence (n = 24) was performed. Each participant received salbutamol 4 mg, ambroxol 15 mg, salbutamol 4 mg co-administered with ambroxol 15 mg or fixed-dose combination formulation (salbutamol 4 mg and ambroxol 15 mg). Plasma concentrations of two analytes were determined with the use of validated LC-MS/MS method. Safety and tolerability were assessed by recording adverse events. RESULTS: Co-administration of salbutamol and ambroxol was not associated with a significant influence on single salbutamol or ambroxol pharmacokinetics. After statistical comparisons of log-transformed Cmax and AUC of salbutamol and ambroxol between fixed-dose combination and concomitant treatments, all 90% confidence intervals of geometric mean ratios were within the predefined equivalence range of 80 - 125%. No serious adverse events were reported, and all treatments were safe and well tolerated in Chinese healthy subjects. CONCLUSION: There were no significant drug-drug pharmacokinetic interactions between salbutamol and ambroxol after oral administration. The new formulation was bioequivalent to the co-administration of two drugs in separate dosage forms.
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Bioequivalence assessment of ambroxol orally-disintegrating tablet after a single oral-dose administration to healthy volunteers.

OBJECTIVE: In this study, a modified LC-MS/MS method was used to determine plasma ambroxol concentration and thereby examine the bioequivalence of two ambroxol medications among healthy Chinese male volunteers. METHODS: The study used a single-dose, randomized, open-label design principle and calculated pharmacokinetic parameters for the comparison of the two formulations. RESULTS: Administration of a single oral dose of either the test drug or reference drug was found to be safe in healthy subjects. No severe, serious, or life-threatening clinical or drug-related side effects were reported during the study. The majority of clinical laboratory test results were within the normal range or not clinically significant. The pharmacokinetic parameters for ambroxol oral tablets and ambroxol orally disintegrating tablets were comparable. For the comparison of the two formulations, the 90% confidence intervals for the log-transformed pharmacokinetic parameters (Cmax, AUC0-t, and AUC0-inf) fell within the bioequivalence< acceptance criteria (80-125%). CONCLUSIONS: The ambroxol oral tablets were bioequivalent to ambroxol orally-disintegrating tablets in healthy human adult male volunteers, under fasting conditions.

Pharmacokinetics and bioequivalence study of three oral formulations of ambroxol 30 mg: a randomized, three-period crossover comparison in healthy volunteers.

OBJECTIVE: To compare the pharmacokinetic properties of two newly developed generic ambroxol formulations with a branded innovator product in healthy Chinese male volunteers. METHODS: This was a single-dose, randomized, open-label, three-period crossover study in healthy volunteers aged 18 - 45 years under fasting conditions. Subjects were assigned to receive 1 of 2 test formulations or a reference tablet of ambroxol 30 mg. Each study period was separated by a 1-week washout phase. Blood samples were collected at pre-specified times. A non-compartmental method was employed to determine pharmacokinetic properties (C(max), t(max), AUC(0-tlast), AUC(0-∞)) to test for bioequivalence. The predetermined regulatory range of 90% CI for bioequivalence was 80 - 125%. RESULTS: 24 subjects were enrolled in and completed the study. The geometric mean C(max) values for the test tablet, test capsule, and reference product were 82.73, 85.36, 84.56 ng/mL, and their geometric mean AUC(0-tlast) (AUC(0-∞)) were 660.87 (753.49), 678.98 (756.79), and 639.41 (712.14) ng x h/mL, respectively. For test tablet vs. reference, the 90% CIs of the least squares mean test/reference ratios of C(max), AUC(0-tlast), and AUC(0-∞) were 91.2% to 104.9%, 96.5% to 110.7%, and 98.8% to 113.4%, respectively. For test capsule, the corresponding values were 94.1% to 108.3%, 99.2% to 113.7%, and 99.2% to 113.9%, respectively. No adverse events occurred during the study. CONCLUSIONS: The ambroxol 30 mg tablets and capsules were considered bioequivalent to the reference formulation in accordance with predetermined regulatory criteria.

Design and evaluation of osmotic pump-based controlled release system of Ambroxol Hydrochloride.

The purpose of the present study was to design and evaluate an osmotic pump-based drug delivery system for controlling the release of Ambroxol Hydrochloride (Amb). Citric acid, lactose and polyethylene glycol 6000 (PEG 6000) were employed as osmotic agents. Surelease EC containing polyethylene glycol 400 (PEG 400) controlling the membrane porosity was used as semi-permeable membrane. The formulation of tablet core was optimized by orthogonal design and evaluated by weighted mark method. The influences of the amount of PEG 400 and membrane thickness on Amb release were investigated. The optimal osmotic pump tablet (OPT) was evaluated in different release media and at different stirring rates. The major release power confirmed was osmotic pressure. The release of Amb from OPT was verified at a rate of approximately zero-order, and cumulative release percentage at 12?h was 92.6%. The relative bioavailability of Amb OPT in rabbits relative to the commercial sustained capsule was 109.6%. Our results showed that Amb OPT could be a practical preparation with a good prospect.

[Optimization of a floating osmotic pump system of ambroxol hydrochloride using central composite design-response surface methodology and its pharmacokinetics in Beagle dogs].

This paper reported that a new type of floating osmotic pump of ambroxol hydrochloride was designed. Third method apparatus (Chinese Pharmacopeia 2010, appendix XD) was employed to simultaneously evaluate the release and floating behavior in vitro. The system was optimized using central composite design-response surface methodology. Similar factor (f2) between the release profile of self-made formulation and the target release profile was chosen as dependent factor. The amount of glucose (A, mg), pore former (B, %) and weight of coating (C, %) were employed as independent factors. Optimized formulation was: A (100.99 mg), B (1.70%), C (4.21%). The value of f2 (89.14) was higher than that of market capsules (69.02) and self-made tablets (72.15). It was showed that self-made capsules possessed character of zero-order release (r = 0.994 4) and drug release completely (>90%). It was showed in result of in vivo study that tmax and Cmax of self-made capsules were significantly lower than that of market capsules and self-made tablets. The correlation coefficient between the fraction of absorption in vivo and the release rate in vitro was 0.985 1, and relative bioequivalence of self-made capsules was 110.77%. Accordingly, self-made capsules displayed obviously characteristics of controlled release both in vivo and in vitro.

A simple LC-MS/MS method for simultaneous determination of cilostazol and ambroxol in Sprague-Dawley rat plasma and its application to drug-drug pharmacokinetic interaction study following oral delivery in rats.

Recently, a combination of cilostazol and ambroxol has been used in the clinical treatment of stroke-associated pneumonia (SAP). However, the pharmacokinetic drug-drug interaction (DDI) of cilostazol and ambroxol has not been reported. In this paper, a rapid, reproducible and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of cilostazol and ambroxol in Sprague-Dawley (SD) rat plasma was established and validated for the first time. Domperidone was used as the internal standard (IS) and one-step liquid-liquid extraction (LLE) method was used to extract analytes and IS from plasma samples with methyl tert-butyl ether as extractant. A rapid chromatographic separation within 4.8 min was carried on an Ultimate ® XB-C18 column with a mobile phase consisting of methanol-acetonitrile-formic acid (0.1%) aqueous solution (90:2:8, v/v/v) at a flow rate of 500 µL/min. The quantitative detection of the analytes and IS were performed on a positive electrospray ionization mode (ESI), and scanned by multi-reaction monitoring (MRM) with the ion transitions m/z 370.3 â†’ m/z 288.2 for cilostazol, m/z 378.8 â†’ m/z 263.8 for ambroxol and m/z 426.2 â†’ m/z 175.1 for domperidone (IS), respectively. It had good linearity in the range of 5.0-1000 ng/mL for cilostazol and 1.0-200 ng/mL for ambroxol in rat plasma. The methodology was fully validated with selectivity, linearity, lower limits of quantification, precision, accuracy, extraction recovery, matrix effect, stability and carry-over effect. The validated data have met the determination requirements of biological samples in FDA guideline. The method was successfully applied to the pharmacokinetics and DDI study of cilostazol and ambroxol in male SD rats. The current study found that the interaction between cilostazol and ambroxol may be caused by CYP3A4 and the pharmacological properties of cilostazol, which may be helpful for therapeutic drug monitoring, clinical dose reference and provide a valuable tool for drug-drug interactions.

Protein unbound pharmacokinetics of ambroxol in the blood and brains of rats and the interaction of ambroxol with Polygala tenuifolia by multiple microdialysis.

ETHNOPHARMACOLOGICAL RELEVANCE: Ambroxol elevates glucocerebrosidase (GCase) activity and reduces nigrostriatal alpha-synuclein burden to better ameliorate motor function in Parkinson's disease (PD). Polygala tenuifolia is a potential alternative botanical medicine for the treatment of many nonmotor symptoms of PD commonly used in Taiwanese patients. Co-administration of these two medicines pose potential herb-drug interaction. AIM OF THE STUDY: Our hypothesis is that ambroxol and P. tenuifolia may potentially possess herbal drug synergetic effects in the blood and brain. MATERIALS AND METHODS: To investigate this hypothesis, a multiple microdialysis system coupled with validated ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for rat blood and brain samples. Experimental rats were divided into three groups: low-dose and high-dose ambroxol alone (10 mg/kg, i.v. and 30 mg/kg, i.v., respectively) and ambroxol (10 mg/kg, i.v.) pretreated with P. tenuifolia extract (1 g/kg, p.o. for 5 consecutive days). RESULTS: Ambroxol easily penetrated into the brain and reached a maximum concentration in the striatum at approximately 60 min after low- and high-dose treatment. The area under the concentration curve (AUC) ratio increased proportionally at the doses of 10 and 30 mg/kg, which suggested a linear pharmacokinetic manner of ambroxol. The brain penetration of ambroxol was approximately 30-34%, which was defined as the ambroxol AUC blood-to-brain distribution ratio (AUCbrain/AUCblood). The P. tenuifolia extract did not significantly alter the pharmacokinetics of ambroxol in the blood and brain of rats. CONCLUSION: The present study suggests that it is safety without pharmacokinetic interactions for this dosing regimen to use P. tenuifolia extract and ambroxol together.

Transepithelial transport of ambroxol hydrochloride across human intestinal Caco-2 cell monolayers.

This study aimed i) to characterize the transepithelial transport of the mucolytic agent ambroxol hydrochloride across the intestinal barrier, ii) to classify the ambroxol according to Biopharmaceutics Classification System (BCS) and iii) to predict ambroxol absorption in humans. Transport of ambroxol (100, 300 and 1000 micromol/l) was studied in a human colon carcinoma cell line Caco-2 in apical to basolateral and basolateral to apical direction, under iso-pH 7.4 and pH-gradient (6 vs. 7.4) conditions. The relative contribution of the paracellular route was estimated using Ca2+-free transport medium. Ambroxol samples from receiver compartments were analysed by HPLC with UV detection (242 nm). Results showed that ambroxol transport is linear with time, pH-dependent and direction-independent, displays non-saturable (first-order) kinetics. Thus, the transport seems to be transcellular mediated by passive diffusion. Estimated high solubility and high permeability (P(app) = 45 x 10(-6) cm/s) of ambroxol rank it among well absorbed compounds and class I of BCS. It can be expected that the oral dose fraction of ambroxol absorbed in human intestine is high.

Simultaneous determination of amoxicillin and ambroxol in human plasma by LC-MS/MS: validation and application to pharmacokinetic study.

A rapid, simple and sensitive LC-MS/MS method was developed for simultaneous determination of amoxicillin and ambroxol in human plasma using clenbuterol as internal standard (IS). The plasma samples were subjected to a simple protein precipitation with methanol. Separation was achieved on a Lichrospher C(18) column (150 mm x 4.6mm ID, dp 5 microm) using methanol (containing 0.2% of formic acid) and water (containing 0.2% of formic acid) as a mobile phase by gradient elution at a flow rate of 1.0 mL/min. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 365.9-->348.9 (amoxicillin), m/z 378.9-->263.6 (ambroxol) and m/z 277.0-->203.0 (IS). Calibration curves were linear in the concentration range of 5-20,000 ng/mL for amoxicillin, and 1-200 ng/mL for ambroxol, with the intra- and inter-run precisions of <9% and the accuracies of 100+/-7%. The method has been validated and applied to pharmacokinetic studies of compound amoxicillin and ambroxol hydrochloride tablets in healthy Chinese volunteers.

Ambroxol in the 21st century: pharmacological and clinical update.

BACKGROUND: Belonging to the group of expectorants, ambroxol is an active substance with a long history that influences parameters considered to be the basis for the physiological production and the transport of the bronchial mucus. Therefore, ambroxol's indication is 'secretolytic therapy in acute and chronic bronchopulmonary diseases associated with abnormal mucus secretion and impaired mucus transport'. OBJECTIVE: The aim of this review is to evaluate the pharmacological and clinical data on the mucokinetic compound ambroxol. METHODS: The existing database that covers >40 years of pharmacological research and clinical development was analysed. Only studies with adequate study design were evaluated. CONCLUSION: Ambroxol is shown to exert several activities: i) secretolytic activity (i.e., promotes mucus clearance, facilitates expectoration, and eases productive cough); ii) anti-inflammatory and antioxidant activity; and iii) a local anaesthetic effect through sodium channel blocking at the level of the cell membrane. The reduction on chronic obstructive pulmonary disease exacerbations is consistent and clinically relevant. The anaesthetic effect is a new pharmacological action that could be beneficial in the management of acute respiratory tract infections. The efficacy and safety of ambroxol is well established.

In vitro pharmacology of ambroxol: Potential serotonergic sites of action.

AIMS: Ambroxol is a muco-active agent with multiple, clinically relevant effects in the airway. Despite its widespread use and well documented clinical efficacy, there are few data on its mechanism of action and receptor pharmacology beyond sodium channel blockade and inhibition of guanylate cyclase. Accordingly, in vitro studies were conducted to determine its overall receptor pharmacology and possible sites of action. MATERIALS AND METHODS: In vitro radioligand binding/enzyme inhibition studies were conducted at 62 receptors, ion channels and enzymes using standard techniques. Additional in vitro studies were conducted to establish the potency of ambroxol at selected sites. KEY FINDINGS: These studies indicate that ambroxol has affinity for the 5-HT3 serotonin receptor, as well as affinity for the 5-HT serotonin transporter (SERT), with IC50 values of 17,600 nM and 19,500 nM respectively. In vitro functional studies in isolated guinea pig colon indicate that ambroxol is a 5-HT3 serotonin receptor antagonist with an IC50 value of 36,000 nM. SIGNIFICANCE: Together, these studies indicate that ambroxol may exert its beneficial properties via antagonism of the 5-HT3 serotonin receptor and/or inhibition of serotonin uptake (5-HT transport: SERT), in addition to its reported effects at the sodium channel and guanylate cyclase.

Simultaneous determination and pharmacokinetic study of roxithromycin and ambroxol hydrochloride in human plasma by LC-MS/MS.

BACKGROUND: Although roxithromycin and ambroxol HCl were often administered concomitantly for the treatment of respiratory infections, the pharmacokinetic interactions between them have not been reported. We investigated the interactions between these drugs in health male Chinese volunteers by LC-MS/MS in human plasma. METHODS: The pharmacokinetics were studied in 12 healthy male Chinese volunteers after an overnight fast by a single oral dose, 4-way crossover design with a period of 7-day washout. Each subjects was randomized to receive a single oral dose of 1 compound roxithromycin (150 mg) and ambroxol HCl (30 mg) dispersible tablet (test formulation, treatment A), one 150 mg roxithromycin dispersible tablet together with one 30 mg ambroxol HCl tablet (combined reference formulations, treatment B), one 150 mg roxithromycin dispersible tablet (reference formulation I, treatment C), or one 30 mg ambroxol HCl tablet (reference formulation II, treatment D) with 250 ml of water. Venous blood was collected at pre-dose (0 h) and 0.25, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24, 48, 72 h after dosing. The plasma concentrations of roxithromycin and ambroxol HCl were simultaneously determined by using a validated internal standard LC-MS/MS method. RESULTS: No significant differences were observed for the major pharmacokinetic parameters such as C(max), T(max), t(1/2) and AUC of both roxithromycin and ambroxol HCl between different treatments. CONCLUSION: The pharmacokinetics of both roxithromycin and ambroxol HCl are not affected by their concomitant oral administration. Therefore, there are no obvious pharmacokinetic interactions between roxithromycin and ambroxol HCl after oral administration. Roxithromycin and ambroxol HCl dispersible tablets were bioequivalent with reference to the roxithromycin dispersible tablets and ambroxol HCl tablets in combination usage.

In situ gelling pectin formulations for oral drug delivery at high gastric pH.

The aim of the study was to compare the gelation and drug release characteristics of formulations of pectin with high (31%) and low (9%) degrees of methoxylation over a wide pH range (pH 1.2-5.0). Dilute solutions of pectin (1.5%, w/v) containing complexed calcium ions formed gels in vitro at low pH (pH<2.5) as a consequence of cross-linking of the galacturonic chains by calcium ions released from the complex, but the efficiency of gelation was significantly reduced with increase of pH because of incomplete release of complexed Ca(++). Gelation of formulations of pectin with a degree of esterification of 9% (DE9) was observed over the pH range 2.5-5.0 in the presence of 1.6mM Ca(++), but was incomplete in formulations of pectin with a degree of esterification of 31% (DE31). A sustained release of ambroxol was observed following oral administration of pectin DE9 formulations to gastric-acidity controlled rabbits at pH 5.5-5.7 and visual observation of the stomach contents of these rabbits confirmed in situ gelation of these formulations. There was no evidence of in situ gelation of pectin DE31 formulations under these conditions and a rapid initial drug release was observed. Differences in gelling characteristics in this pH range were attributed to the greater susceptibility of low methoxylated pectin to cross-linking by di- and tri-valent ions present in the gastric juice. It is concluded that formulations of pectin with a low degree of esterification have potential application as in situ gelling vehicles for the sustained delivery of drugs following oral administration under conditions of high gastric pH.

[Determination of ambroxol and clenbuterol in human plasma by LC-MS/MS method].

Ambroxol and clenbuterol were extracted from human plasma samples by liquid-liquid extraction, ambroxol was separated on a Zorbax XDB-C18 column and detected by tandem mass spectrometry with an atmospheric pressure chemical ionization interface after oral administration of a compound preparation. Clenbuterol was separated on a Zorbax XDB-C8 column and detected by tandem mass spectrometry with an electrospray ionization interface. Diphenhydramine is used as the internal standard. The linear concentration ranges of the calibration curves for ambroxol and clenbuterol were 0.080 - 400 microg x L(-1) and 5.0 - 5 000 ng x L(-1), respectively. The lower limits of quantification were 0.080 microg x L(-1) for ambroxol and 5.0 ng x L(-1) for clenbuterol, individually. The inter-day and intra-day precision (RSD) across three validation run over the entire concentration range was below 7.5%, and the accuracy (RE) was within +/- 2.5% for both ambroxol and clenbuterol. The methods were used to determine the pharmacokinetic parameters of ambroxol and clenbuterol in human plasma after oral administration of a compound preparation containing 60 mg ambroxol hydrochloride and 40 microg clenbuterol hydrochloride. The method was proved to be highly sensitive, selective and suitable for the pharmacokinetic study of different compound preparations containing ambroxol and clenbuterol.

Quantitative Detection of Ambroxol in Human Plasma Using HPLC-APCI-MS/MS: Application to a Pharmacokinetic Study.

In this study, a rapid and reliable high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the determination of ambroxol in human plasma was developed and validated using palmatine as an internal standard (IS). Ambroxol and IS were extracted from 200 µL of human plasma via a simple protein precipitation preparation. Chromatographic separation was achieved on a Platisil C18 column (150 × 4.6 mm, 5 µm) using methanol-0.01% formic acid (70:30, v/v) as the mobile phase at a flow rate of 0.6 mL/min under an isocratic condition. The MS acquisition m/z 379 → 264 for ambroxol and 352 → 336 for IS was performed by atmospheric-pressure chemical ionization (APCI) mass spectrometry in selected reaction monitoring mode. The calibration curve for ambroxol was linear over the concentration range of 2.500 - 180.0 ng/mL. The matrix effects of ambroxol ranged from 104.6 to 112.7%. This fully validated method was successfully applied to a pharmacokinetic study of ambroxol in humans after oral administration of ambroxol at a single dose of 75 mg.