Development and validation of column-switching high-performance liquid chromatographic methods for the determination of a potent AII receptor antagonist, TCV-116, and its metabolites in human serum and urine

Quantitative bio-analysis of pitavastatin and candesartan in rat plasma by HPLC-UV: Assessment of pharmacokinetic drug-drug interaction

A novel, precise, accurate and rapid HPLC-UV method was developed, optimised and fully validated for simultaneous estimation of pitavastatin (PIT) and candesartan (CAN) in rat plasma using telmisartan as an internal standard. Following liquid-liquid extraction of the analytes from plasma, chromatographic separation was accomplished on a Waters Reliant C18 column (4.6 × 250 mm, 5 µm) using ACN-5 mM Sodium acetate buffer (80:20, v/v; pH adjusted to 3.5 with acetic acid) as mobile phase at a flow rate of 0.8 mL/min and wavelength of 234 nm. The calibration curves were linear over the concentration ranges of 2-400 ng/mL and 3-400 ng/mL for pitavastatin and candesartan respectively. The method when validated as per US-FDA guidelines was found to be precise as well as accurate. Extraction recovery observed for both analytes was above 90% as well as reproducible and consistent. Stability studies showed the samples to be stable over a long period covering from sample collection to final analysis. The method was successfully applied to investigate pharmacokinetic interaction between PIT and CAN in wistar rats. The mean plasma concentration-time curves of PIT and CAN showed that single PIT as well as CAN show similar pharmacokinetic properties to those obtained when co-administrated with each other (P value >0.05). Hence, there is no evidence for a potential drug-drug interaction between PIT and CAN. This information provides evidence for clinical rational use of CAN and PIT in cardiovascular patients.

A simple, rapid and fully validated HPLC method for simultaneous quantitative bio-analysis of rosuvastatin and candesartan in rat plasma: Application to pharmacokinetic interaction study

A simple, precise and accurate HPLC method was developed, optimized and validated for simultaneous determination of rosuvastatin and candesartan in rat plasma using atorvastatin as an internal standard. Solid-phase extraction was used for sample cleanup and its subsequent optimization was carried out to achieve higher extraction efficiency and to eliminate matrix effect. A quality by design approach was used, wherein three-level factorial design was applied for optimization of mobile phase composition and for assessing the effect of pH of the mobile phase using Design Expert Software. Adequate separation for both analytes was achieved with a Waters C₁₈ column (250 × 4.6 mm, 5 μm) using acetonitrile-5 mm sodium acetate buffer (70:30, v/v; pH adjusted to 3.5 with acetic acid) as a mobile phase at a flow rate of 1.0 mL/min and wavelength of 254 nm. The calibration curves were linear over the concentration ranges 5-150 and 10-300 ng/mL for rosuvastatin (ROS) and candesartan (CAN), respectively. The validated method was successfully applied to a pharmacokinetic study in Wistar rats and the data did not reveal any evidence for a potential drug-drug interaction between ROS and CAN. This information provides evidence for clinical rational use of ROS and CAN.

Effect of surfactants and hydrophilic polymers on the stability of an antihypertensive drug candesartan cilexetil: Evaluation by HPLC

OBJECTIVES

The objective of this study is to investigate the effect of surfactants (polysorbate 80 and sodium lauryl sulphate) and hydrophilic polymers (polyvinylpyrrolidone and polyethylene glycol 6000) on the stability of candesartan cilexetil under isothermal stress conditions (100°C, 48h).

METHODS

HPLC method was employed to evaluate the drug content and formation of degradation products in stress samples. Drug and degradation products were separated on Hypersil BDS C18 (250×4.6mm, 5μ) column using acetonitrile-water (pH 2.8) in the ratio of 85:15% v/v as a mobile phase.

RESULT

Similar degradation behaviour of drug was observed with polyvinylpyrrolidone, polyethylene glycol 6000 and polysorbate 80; four common degradation peaks were observed at the retention time of 3.7, 4.5, 7.8 and 11minutes. One extra common degradation peak of very low intensity was also observed with polyethylene glycol 6000 and polysorbate 80 at the retention time of 4.2min. The drug was eluting at the retention time of 5.4min. In the case of sodium lauryl sulphate, two prominent degradation peaks were observed at the retention time of 3.7 and 13.25min along with few very low-intensity degradation peaks.

CONCLUSION

The drug showed 41%, 64%, 72% and 98% degradation in presence of polyvinylpyrrolidone, polyethylene glycol 6000, polysorbate 80 and sodium lauryl sulphate, respectively.

Angiotensin II AT(1) receptor blockers ameliorate inflammatory stress: a beneficial effect for the treatment of brain disorders

Excessive allostatic load as a consequence of deregulated brain inflammation participates in the development and progression of multiple brain diseases, including but not limited to mood and neurodegenerative disorders. Inhibition of the peripheral and brain Renin-Angiotensin System by systemic administration of Angiotensin II AT(1) receptor blockers (ARBs) ameliorates inflammatory stress associated with hypertension, cold-restraint, and bacterial endotoxin administration. The mechanisms involved include: (a) decreased inflammatory factor production in peripheral organs and their release to the circulation; (b) reduced progression of peripherally induced inflammatory cascades in the cerebral vasculature and brain parenchyma; and (c) direct anti-inflammatory effects in cerebrovascular endothelial cells, microglia, and neurons. In addition, ARBs reduce bacterial endotoxin-induced anxiety and depression. Further pre-clinical experiments reveal that ARBs reduce brain inflammation, protect cognition in rodent models of Alzheimer's disease, and diminish brain inflammation associated with genetic hypertension, ischemia, and stroke. The anti-inflammatory effects of ARBs have also been reported in circulating human monocytes. Clinical studies demonstrate that ARBs improve mood, significantly reduce cognitive decline after stroke, and ameliorate the progression of Alzheimer's disease. ARBs are well-tolerated and extensively used to treat cardiovascular and metabolic disorders such as hypertension and diabetes, where inflammation is an integral pathogenic mechanism. We propose that including ARBs in a novel integrated approach for the treatment of brain disorders such as depression and Alzheimer's disease may be of immediate translational relevance.

Candesartan reduces the innate immune response to lipopolysaccharide in human monocytes

OBJECTIVE

Inhibition of angiotensin II receptor type 1 (AT1) reduces chronic inflammation associated with hypertension. We asked whether AT1 receptor inhibition would reduce the innate inflammatory response induced by bacterial lipopolysaccharide (LPS).

METHODS

We used unstimulated human circulating monocytes obtained from healthy donors by counterflow centrifugal elutriation. Monocytes were studied in vitro after incubation with LPS (50 ng/ml) with and without 1 mumol/l candesartan, an AT1 receptor blocker. Angiotensin II receptor mRNA expression was determined by reverse transcriptase-PCR and receptor binding by autoradiography; inflammatory factor mRNA expression was studied by reverse transcriptase-PCR and cytokine release by ELISA.

RESULTS

Human monocytes did not express detectable AT1 receptors, and angiotensin II did not induce inflammatory factor mRNA expression or cytokine release. However, candesartan substantially reduced the LPS-induced expression of the mRNAs for the LPS recognition protein cluster of differentiation 14, the proinflammatory cytokines tumor necrosis factor alpha, interleukin-1 beta and interleukin-6 and the lectin-like oxidized low-density lipoprotein receptor. In addition, candesartan reduced the activation of the nuclear factor kappa B pathway, the tumor necrosis factor alpha and interleukin-6 secretion, and the ROS formation induced by LPS, without affecting the secretion of interleukin-10.

CONCLUSION

We hypothesize that the anti-inflammatory effects of candesartan in these cells are likely mediated by mechanisms unrelated to AT1 receptor blockade. Our results demonstrate that candesartan significantly reduces the innate immune response to LPS in human circulating monocytes. The anti-inflammatory effects of candesartan may be of importance not only in hypertension but also in other inflammatory disorders.

Clinical pharmacokinetics of candesartan

Candesartan cilexetil is the prodrug of candesartan, an angiotensin II type 1 (AT1) receptor antagonist. Absorbed candesartan cilexetil is completely metabolised to candesartan. Oral bioavailability is low (about 40%) because of incomplete absorption. Plasma protein binding in humans is more than 99%. The volume of distribution in healthy individuals is 0.13 L/kg. CV-15959 is the inactive metabolite of candesartan. Candesartan that reaches the systemic circulation is mainly cleared by the kidneys, and to a smaller extent by the biliary or intestinal route. The apparent oral clearance of candesartan is 0.25 L/h/kg after a single dose in healthy individuals. Oral clearance (3.4 to 28.4 L/h) is highly variable among patients. No relevant pharmacokinetic drug-food or drug-drug interactions are known. The terminal elimination half-life remains unclear, but appears to be longer than the currently used range of 4 to 9 hours. Non-compartmental models do not appear to be appropriate for the analysis of candesartan pharmacokinetic data. A 2-compartment analysis revealed a much longer half-life of 29 hours using data from patients with hypertension. However, a further indepth analysis has never been performed. The concentration-effect relationship is unaffected by age. No gender or race differences have been shown in the effect or pharmacokinetics of candesartan. Renal function affects the pharmacokinetic profile of candesartan. For patients with creatinine clearances of >60 ml/min x 1.73m(2), 30 to 60 ml/min x 1.73m(2) and 15 to 30 ml/min x 1.73m(2), the elimination half-life is 7.1, 10.0 and 15.7 hours, respectively, at a dose of 8 mg/day. However, at 12 mg/day an accumulation factor of 1.71 was found. Thus, a maximum daily dose of up to 8mg appears suitable in patients with severe renal dysfunction. No significant elimination of candesartan occurs with haemodialysis. In patients with mild to moderate hepatic impairment, no relevant pharmacokinetic alterations have been observed. Dosages of up to 12 mg/day do not require precautions in patients with mild to moderate liver disease. Clinically effective dosages range between 8 and 32 mg/day. The response rate of monotherapy with candesartan in patients with hypertension increases with dosage, but never exceeds 60% at a daily dosage of 16mg of candesartan. Dosages up to 32 mg/day do not increase this response rate.

Determination of candesartan cilexetil, candesartan and a metabolite in human plasma and urine by liquid chromatography and fluorometric detection

Liquid chromatographic methods are described for the determination of a new effective anti-hypertensive drug candesartan (CV-11974), its prodrug candesartan cilexetil (TCV-116) and a metabolite, CV-15959 in human plasma and urine. The assays comprise liquid-liquid extraction and separation on a phenyl column with fluorometric detection. The methods give absolute recoveries of 70, 83 and 78% for candesartan cilexetil, candesartan and CV-15959, respectively, and the limit of quantification is 5, 1 and 3 nM of plasma (RSD < 20%), respectively. The methods were applied to plasma and urine samples from biopharmaceutical and clinical studies in man.

Double column-switching high-performance liquid chromatographic method for the determination of TAK-603 and its metabolites in human serum

A double column-switching high-performance liquid chromatographic (HPLC) method for the determination of concentrations for TAK-603 (T) and its metabolites, T-72258 (M-I) and T-72294 (M-III), in human serum was developed. The analytes were extracted with ethyl acetate from human serum samples treated with triethylamine and injected into the HPLC system. Separation of the analytes was performed on the HPLC system with double column-switching technique. The mobile phases A and B for the first column and the mobile phase C for the second column used were a mixture of methanol-10 mM aqueous ammonium acetate solution (1:1, v/v), methanol and a mixture of methanol-10 mM aqueous ammonium acetate solution (11:9, v/v), respectively. The eluate was monitored with a UV detector at a wavelength of 253 nm. The work-up procedure was reproducible and more than 90% of the analytes could be recovered from human serum. The lower limits of quantitation were all 1 ng/ml for the analytes when 0.5 ml of human serum was used. Standard curves were linear with a correlation coefficient (R) of more than 0.999 in the range of 1-500 ng/ml for T, M-I and M-III in human serum. The intra- and inter-day precision of the method for the various analytes were below 4.8%. The accuracy was good with the deviations between spiked and calculated concentrations of the analytes being within 11.0%. The method was successfully applied to analyze serum samples after an oral administration of T to healthy male volunteers.

Angiotensin II antagonism and plasma radioreceptor-kinetics of candesartan in man

AIMS

The pharmacodynamic properties of the angiotensin II antagonist candesartan in humans were assessed from the rightward shifts of angiotensin II dose-effect curves (Schild regression technique). The pharmacokinetic characteristics were determined by radioreceptor assay (r.r.a.) and h.p.l.c.

METHODS

Twelve healthy male volunteers received single oral doses of 4, 8 and 16 mg candesartan cilexetil and placebo. Plasma was obtained for h.p.l.c. and r.r.a. (receptors: rat lung; radioligand: [125I-Sar1Ile8]-angiotensin II). Before and up to 24 h post dosing angiotensin II was infused in ascending dose steps until blood pressure (systolic and/or diastolic) increased by +25 mmHg. Individual angiotensin II dose-effect curves were fitted according to an Emax model and dose ratios (DR) calculated from the antagonist induced rightward shifts.

RESULTS

Candesartan, the active metabolite of candesartan cilexetil, declined from peak concentrations at about 4 h with a t1/2 of about 6 h. A linear relation (slope 1) between h.p.l.c. and r.r.a. data revealed that there is no other active metabolite. DR at 6-9 h post dosing reached a maximum of about 30 and at 24 h still amounted to 4-7, indicating the persistence of a relevant antagonistic effect in vivo. The apparent Ki-doses (derived from Schild regression plots) indicated a high potency (1.9 mg at 24 h) and slow decline of effect. Between plasma concentrations and antagonistic effect a counterclockwise hysteresis was visible.

CONCLUSIONS

A longer persistence of the antagonistic effect at the receptor site than expected by the presence in plasma indicates a slow off-rate of candesartan cilexetil from in vivo receptors. This provides an additional rationale for the observed 24 h therapeutic activity of candesartan cilexetil.

Taxol content of various Taxus species in Hungary

The anticancer drug taxol was separated and quantitatively determined in bark and foliage of different Taxus species by high-performance liquid chromatography to prove the presence of taxol in Hungarian Taxus species. The measurements were carried out with photodiode array detection using a porous graphitized carbon column, and a water:dioxan 54:46 v/v eluent. Taxol was established as being present in measurable amounts in each Hungarian Taxus species. According to the results bark was richer in taxol than foliage. It could also be observed that the older the bark or foliage, the more taxol it contained. The validation process proved that the method is reliable and can be used for the separation and quantitative determination of taxol in both the bark and foliage of Taxus species grown in Hungary.