HPLC-UV dissolution testing using ELGA’s PURELAB® Ultra system enhances therapeutic drug monitoring

27 Feb 2018

In the pharmaceutical industry, generic substitution has played an important role in limiting the cost of medicines in many countries. However, some concerns have been raised regarding the testing of generic substitutes, particularly those that are narrow therapeutic index drugs (NTIDs), such as ciclosporin, a potent immunosuppressant. NTIDs are characterized by a small difference between their minimum effective concentration and their minimum toxic concentration in blood. This means that just a small increase in dose or in blood/serum concentration of NTIDs can lead to toxic effects in patients.

Given the risks involved with ciclosporin generics, it is important to demonstrate that the branded drug and the substitute have comparable drug content and purity. A widely used technique for such therapeutic drug monitoring is high-performance liquid chromatography (HPLC), which is highly sensitive and specific. However, current HPLC methods are unable to detect whether unknown impurities have interfered with ciclosporin, calling into question the reliability and reproducibility of therapeutic monitoring of this drug.

A recent study by Dr. Badr Aljohani and colleagues set out to develop, validate, and apply an improved HPLC method for detecting the active drug content and impurities in ciclosporin capsules.(1) The assay used dissolution testing, which involves rupturing the capsule in a medium (such as ultrapure water), and then measuring the dissolved contents via HPLC-UV mass spectrometry. Using ultrapure water was crucial to the success of this study to avoid any impurities interfering with the highly sensitive liquid chromatography method.(2) For this purpose, Aljohani’s team used the ELGA PURELAB Ultra water purification system to obtain deionized water as the dissolution medium.(3)

A HPLC-UV method for dissolution testing

For over thirty years in the pharmaceutical industry, ciclosporin has been produced to prevent rejection after organ or tissue transplants, and to treat autoimmune disorders, such as Crohn’s disease and rheumatoid arthritis. However, treatment may be associated with several adverse drug reactions (ADRs), including convulsions, high blood pressure, kidney and liver dysfunction, and can lead to an increased risk of developing lymphoma.

Aljohani’s laboratory aimed to analyze the active drug base and/or any impurities in ciclosporin capsules, which could result in ADRs in patients. The team analyzed the drug content of seven ciclosporin products, which were either brands or generics obtained from seven different countries (Columbia, Egypt, India, Jordan, Pakistan, Saudi Arabia, and Turkey). They used a dissolution test for ciclosporin obtained from US Pharmacopeia 2008, and HPLC-UV was used to separate, identify, and quantitate the components in the liquid samples.

The dissolution test involved rupturing and dissolving the ciclosporin capsules in 500 mL of HPLC-grade deionized water at a purity of 18.2 MO cm, obtained using an ELGA PURELAB® Ultra water purification system. The conditions used by the researchers included a temperature of 37.5 ± 0.5°C, a 5 mL sample volume (filtered using 20 µm filters), and sampling times of 5, 10, 15, 30, 60, and 90 minutes to check for ciclosporin release from capsules.

Pressurized samples (2 mg/mL) of the standard ciclosporin solution were passed through a HPLC-UV system with a UV detection wavelength of 210 nm. Separation was carried out using a reversed phase C18 column, maintained at 50°C, and an injection volume of 20 µL. The analytes were eluted by isocratic elution at a flow rate of 0.7 mL/minute with acetonitrile and water (70:30%, v/v) and 0.03% v/v trifluoroacetic acid, over a 25-minute runtime.

The crucial role of ELGA’s water purification systems

Aljohani’s laboratory developed a simple, rapid, and sensitive HPLC method using dissolution testing to analyze the contents of ciclosporin, and to compare the drug content and purity of generics and brands. In this study, all of the capsules tested were found to contain one or more impurities, and the active drug base did not always match the labelled amount in both generics and brands. The authors noted that this could indicate that switching among and between branded and generic ciclosporin may potentially lead to undesirable effects in patients. However, this is based on only one study using ciclosporin products manufactured in just seven countries, so further work is needed to examine whether these results represent ciclosporin manufacture worldwide.

Such crucial insights using highly sensitive HPLC-UV methods can only be obtained using ultrapure water. Ultrapure water not only avoids damage to expensive equipment but also prevents contamination of the sample medium to help ensure reliable results. The ELGA PURELAB Ultra system used in Aljohani et al.’s research not only offers laboratories the highest quality HPLC-grade water but is also easy to use. Applying such systems to drive forward cutting-edge research in the pharmaceutical industry could therefore reveal more insights to protect patients’ health.

If you’d like to find out more about why ultrapure water is vital for HPLC applications, why not download ELGA’s Water Essence of the Lab whitepaper?

References
[1] http://www.openaccessjournals.com/scholarly-articles/development-and-validation-of-a-hplcuv-method-for-dissolution-testing-of-ciclosporin-its-application-to-the-measurement-of-brand-a-jbb-1000354.pdf
[2] https://www.elgalabwater.com/applications/liquid-chromatography
[3] https://www.elgalabwater.com/products/purelab-ultra