Assessing Specificity in Potentiometric Assays

Specificity in a potentiometric assay refers to the ability of the method to measure the analyte of interest without interference from other substances. This is crucial to ensure accurate and reliable results.

Methods to Assess Specificity

Here are some common methods to evaluate the specificity of a potentiometric assay:

 * Blank Analysis:

   * Purpose: To determine the baseline signal or response in the absence of the analyte.

   * Procedure: Prepare a blank sample containing all the reagents and solvents used in the assay except for the analyte. Measure the potential or response.

   * Evaluation: If the blank signal is significantly low compared to the signal obtained with the analyte, it indicates good specificity.

 * Matrix Effect Study:

   * Purpose: To investigate how different matrices (e.g., excipients, impurities) can affect the assay's response.

   * Procedure: Prepare samples with varying concentrations of the analyte in different matrices. Measure the potential or response.

   * Evaluation: Compare the results obtained with the analyte in different matrices. If there are no significant differences, the assay is less susceptible to matrix effects.

 * Interference Studies:

   * Purpose: To identify potential interfering substances that may affect the assay's accuracy.

   * Procedure: Add known amounts of potential interfering substances to samples containing the analyte. Measure the potential or response.

   * Evaluation: Compare the results obtained with and without the interfering substances. If the interfering substances significantly affect the assay's response, it indicates a lack of specificity.

 * Spike Recovery Studies:

   * Purpose: To assess the accuracy of the assay in the presence of potential interfering substances.

   * Procedure: Add known amounts of the analyte to samples containing potential interfering substances. Measure the potential or response.

   * Evaluation: Calculate the recovery percentage of the spiked analyte. A recovery percentage close to 100% indicates good accuracy and specificity.

Additional Considerations

 * Selectivity of the Electrode: The selectivity of the electrode used in the potentiometric assay is crucial for specificity. A highly selective electrode will minimize interference from other ions or substances.

 * Sample Preparation: Proper sample preparation can help to reduce interference from matrix components. This may involve steps like filtration, dilution, or extraction.

 * Method Optimization: The assay conditions, such as pH, temperature, and ionic strength, can be optimized to improve specificity.

By carefully considering these factors and employing appropriate specificity assessment methods, you can ensure the reliability and accuracy of your potentiometric assays.

Would you like to discuss a specific potentiometric assay or explore any of these methods in more detail?

Warning Letter to US Company due to Lack of Product and Process Control

On 05 August, the FDA issued a warning letter to the US company LS Promotions Inc. in Hicksville. The warning letter is the result of a review of the company's responses to a 483 letter from the FDA. It summarises the violations of Current Good Manufacturing Practice (CGMP) for finished drug products under Title 21 Code of Federal Regulations (CFR), parts 210 and 211 (21 CFR parts 210 and 21) found during the inspection as follows.

Laboratory Testing

Adequate laboratory testing was not performed on each batch of manufactured drug product prior to release to ensure compliance with specifications, including the identity and strength of the active ingredients. Similarly, microbiological testing was not carried out, although this is required for certain products, such as SPF 15 lip balm, SPF 30 sunscreen and hand sanitiser. The lack of testing means that it is not certain whether the products meet the specifications. The FDA therefore expects the company to provide a list of chemical and microbial tests, an action plan for conducting reserve sample analyses and a summary of the test results, including the measures to be taken in the event of substandard quality.

Stability

A suitable testing programme to assess the stability of the medicinal products to determine storage conditions and expiry dates was also missing. There was a lack of robust data to demonstrate that the chemical and microbiological properties remain acceptable throughout the shelf life. In the response to the 483 form after the inspection, there were also no details of any planned stability studies, particularly for products such as SPF 30 sunscreen and hand sanitisers. Without these studies, there is no scientific basis to ensure quality until the expiration date. Therefore, the FDA requires a comprehensive stability testing plan, including the definition of test methods and a continuous shelf life monitoring programme.

This was also seen in the particular aspect that LS Promotions further processed your supplier's SPF 15- lip balm bulk product by adding additional ingredients prior to bottling, but did not have data to demonstrate the stability of this altered formulation product in the finished containers throughout the shelf life.

Product and Process Control

Adequate written procedures for production and process control were not established to ensure the quality of the medicinal products manufactured. There was insufficient validation of manufacturing processes, including cleaning of production equipment. Again, LS Promotions' response was inadequate as neither a detailed validation programme nor a timetable for implementation was provided. A process validation programme covering the entire product life cycle and improvements to the cleaning validation programme are required to ensure that all manufactured products meet quality requirements.

Also in relation to the necessary cleaning and its validation for the filling lines used for multiple products was not in place, Here the FDA requires validation with worst case scenarios such as:

Drugs with higher toxicity 

Drugs with higher concentration of active ingredients

Drugs with lower solubility in their cleaning solvents

Drugs with properties that make them difficult to clean

Swabbing sites for the most difficult to clean areas

Maximum holding times before cleaning

Poor change control management was also identified in this context.

Responsibility and authorisation of the quality units

In general, the FDA found that the Quality Unit (QU) did not fulfil its responsibility to ensure that the manufactured drug products comply with CGMP requirements. Adequate procedures to define the responsibilities of the QU, verify the identity of ingredients and ensure control over labelling were also lacking. No detailed plans for revising the QU procedures were submitted. Therefore, the FDA expected a comprehensive assessment and remediation plan to strengthen the QU, including review of procedures and oversight of production processes.

Further details can be found in the corresponding Warning Letter at the FDAs website.

EMA/CMDh: Q&A Document Nitrosamines revised

In July 2024, the nitrosamine Q&A document "Nitrosamines EMEA-H-A5(3)-1490 - Questions and answers for marketing authorization holders / applicants on the CHMP Opinion for the Article 5(3) of Regulation (EC) No 726/2004 referral on nitrosamine impurities in human medicinal products" of the EMA/CMDh was revised again and published on the EMA website under "Questions and answers".

This list of questions and answers was first published in 2020. The new version 21 now contains updates and changes in the following questions and their answers:

• 8. How should confirmatory tests be conducted by MAHs and manufacturers?
• 9. What are the requirements of the analytical method(s)?
• 10. Which limits apply for nitrosamines in medicinal products?
• 14. What is the approach for new and ongoing marketing authorisation applications (MAA)? 
• 15. When should a test for nitrosamines be included in the MA dossier?
• 16. What are the responsibilities of MAHs for APIs with CEPs or ASMFs?

The current version of the Q&A document "Nitrosamines EMEA-H-A5(3)-1490 - Questions and answers for marketing authorisation holders / applicants on the CHMP Opinion for the Article 5(3) of Regulation (EC) No 726/2004 referral on nitrosamine impurities in human medicinal products"

TGA introduces shorter Surveillance Inspections

From 1 July 2024, the Australian TGA will introduce, at least temporarily, new regulations for GMP inspections of domestic and foreign manufacturers of medicinal products, active pharmaceutical ingredients (APIs), biological products and blood products, so-called surveillance inspections.

These are repeat inspections of manufacturers with a shorter duration, but according to the TGA with full scope. This means that the inspection should cover all aspects of the pharmaceutical quality system (PQS) and the operations, but be reduced by around 50 % of the usual inspection time.

The GMP certificates issued after the inspection will then state that a surveillance inspection has been carried out.

Who is eligible for this?

Both domestic and foreign manufacturers who received a "good" or "satisfactory" rating (A1 or A2) in their last TGA inspection. However, there are also clearly defined exceptions where shortened inspections are not possible.

Objectives

The primary aim is to reduce overdue re-inspections to a level commensurate with the manufacturer's risk and to reduce business disruption caused by delays in re-inspections

Is it possible to remove a Biofilm in pharmaceutical Water Systems?

advantage is that the increased temperature also reaches areas that are difficult to access, such as branch pipes, if the duration of the thermal sanitization is long enough. Temperatures of 70-80 °C are common. Hot systems are therefore self-sanitizing.

Conclusion

The removal of biofilms from pharmaceutical water systems is difficult. Therefore, the measure should not be the removal of a biofilm, but the prevention of such a biofilm. An appropriate system design is essential for this (no dead leg, stub lines, cold spots, etc.). Ozonization of the system is very helpful in preventing biofilm. Regular heating of the entire system is also a good prevention strategy. The most important aspect, however, is to avoid stagnant water. This applies to the entire system as well as to individual components, which should be able to be drained. The water system should therefore not be left standing over the weekend, but should rather be producing water in the design. The motto is: "keep it running!"

Change Control and (Re)Validation - The FDA Perspective

The topic of revalidation is rarely mentioned in the regulations. Ongoing/continued process verification has replaced regular revalidation (with exceptions in the sterile area). But what can happen after a change control? Read the FDA's opinion below.

In a Warning Letter, the FDA describes what it expects in the event of a change in the process. What is it about?

The lack of sufficient validation was criticised. In addition, as a result of customer complaints regarding the viscosity of the product, the company changed two ingredients without change control. The new process was not (re)validated. The FDA does not explicitly refer to revalidation here, but only validation. With reference to its process validation guideline, the FDA then explains what it understands by process validation.

The company's response that it had initiated a structured approach to process validation was not sufficient for the FDA. The authority requires the demonstration of appropriate process validation procedures and plans. Furthermore, the FDA would like to see a timeline for the implementation of CAPA measures or risk assessments on products that have been released without appropriate validation or testing.

The FDA further requires

A plan to ensure that there is continuous monitoring throughout the manufacturing lifecycle of all medicinal products. 

A data-driven and science-based programme to identify process variability and ensure that the necessary parameters and product quality are maintained. 

A summary of the validation programme to ensure that a state of control is maintained throughout the product life cycle, together with the associated procedures. 

A description of the Process Performance Qualification (PPQ) programme 

A description of the monitoring activities to assess intra-batch and inter-batch variability to ensure state of control 

A schedule for the implementation of the PPQ for each of the marketed medicinal products 

A detailed programme for the development, validation, maintenance, control and monitoring of each manufacturing process, with regard to intra- and inter-batch variability to ensure a state of control 

A programme for the qualification of plant and equipment.

Conclusion: Process changes can trigger an event-related (re)validation, whereby the FDA does not use the term revalidation, but only refers to validation.

Containment: What is the Difference between OEB and OEL

In manufacturing, where potentially hazardous substances are handled, concepts such as Occupational Exposure Bands (OEB) and Occupational Exposure Limits (OEL) play a crucial role in employee safety. The two terms, OEB and OEL, are often used interchangeably, but there are clear differences.

What does OEB mean?

OEB stands for Occupational Exposure Bands (OEB). This is a method of classifying substances based on their hazard potential or toxicity, particularly in relation to inhalation exposure. OEBs are usually classified on a scale of 1 to 5, with OEB 1 representing substances with the lowest hazard potential and OEB 5 representing substances with the highest hazard potential. The OEB bands are not standardized, but are defined by companies themselves. So, there can be deviations, which is important for external employees who deal with containment areas of different companies. OEBs should actually be better called iOEBs, for internal Occupational Exposure Bands.

In practice, by specifying the OEBs, a quick and simple classification is possible, which is immediately understandable for the employees. This is safer than, for example, specifying 10-100 µg/m3 when a new product comes into the company and protective measures are explained. "We are receiving an OEB 4 product" is easier than a '1-10 µg/m3 product'.

What does OEL mean?

Occupational Exposure Limits (OEL) are quantified limit values for the permissible exposure of employees to hazardous substances during their work. These limits are usually expressed in ppm or µg/m3 or mg/m3 and are based on the toxic data of the substance and the current state of knowledge about possible health effects. OELs are set by various organizations and authorities, such as the American Conference of Governmental Industrial Hygienists (ACGIH), the European Medicines Agency (EMA) or the Occupational Safety and Health Administration (OSHA).

Differences between OEB and OEL

Although OEBs and OELs are both used to control employee exposure to hazardous substances, there are important differences:

Classification vs. quantification: OEBs classify substances according to their hazard potential, while OELs set quantified exposure limits. 

Subjectivity vs. objectivity: The classification of a substance according to an OEB can be more subjective and based on a comprehensive assessment of various factors, whereas an OEL is based on objective scientific data and threshold values. 

Scope: OEBs are often used to assess the risk of exposures at early stages of development or when information is limited, while OELs serve as specific guidelines to meet exposure limits in practice.

Example

Here is an example to illustrate this: a new active substance in development is provisionally classified as OEB 4 based on limited toxicological data, indicating a high hazard potential and the associated protective measures. Based on subsequent studies and analysis, an OEL of 1 ppm is set to limit employee exposure based on the specific toxicity data.

So, while OEBs classify substances according to their hazard potential in bands or areas, OELs set quantified limits for the permissible exposure of employees. Both concepts complement each other and are crucial to ensure the health and safety of employees through adequate exposure control

FDA Warning Letter on Data Integrity Issues Dominican company Laboratorio Magnachem

On June 18, 2024, the FDA issued a Warning Letter to the Dominican company Laboratorio Magnachem International regarding CGMP violations. The Warning Letter is based on an FDA inspection in November 2023. The company's responses dated December 1, 2023 to the complaints listed in the Form 483 were insufficient in the FDA's view. FDA Warning Letters always reference the GMP requirements set out in 21 CFR Part 211, in this case for data integrity complaints:

"Your firm failed to exercise appropriate controls over computer or related systems to assure that only authorized personnel institute changes in master production and control records, or other records (21 CFR 211.68(a))"

In general, comprehensive control of CGMP data is expected to ensure that all changes, deletions and additions of information to electronic records are authorized and documented.

Observations

The laboratory equipment used to generate analytical data for the release of finished medicinal products has no access protection and no further controls.

There are no adequate controls to prevent data deletion and record alteration

There is no definition of unique user names and passwords

Laboratory staff have administrator rights that allow uncontrolled access to delete or modify HPLC files

There is no way to track individuals who have deleted or modified data generated by the IT system

There are no adequate backup copies of the data generated by the laboratory equipment

Response from the company

The company's responses to this observation were inadequate. Why?

The company stated that it had found a supplier for the management of equipment data and that the HPLC management system was being assessed by this supplier. They had a process in place to address data integrity issues. The FDA was not satisfied with these statements. No interim measures were taken to protect patients and ensure drug quality, e.g.

Notification of customers

Recall of products

Conducting additional tests

Inclusion of batches in the stability program

Increased monitoring of complaints

What does the FDA expect when responding to this Warning Letter?

A complete assessment of the documentation systems used throughout the manufacturing and laboratory operations to determine where documentation procedures are inadequate

A detailed CAPA plan that comprehensively corrects the company's documentation practices to ensure that the company maintains assignable, legible, complete, original, accurate and timely records throughout the operation

A comprehensive, independent assessment and CAPA plan for the security and integrity of the computer system

Interim controls should also be described and details provided of when the procedures for the CAPAs will be implemented

FDA Warning Letter to a Manufacturer of an Athlete Muscle Maintenance Creme

On 9 July, the FDA issued a Warning Letter to a Korean manufacturer registered as a manufacturer of over-the-counter drugs. With the Warning Letter, the FDA is responding to the documents it received from this manufacturer in response to two requests in 2022 and 2024. Since the methods, facilities or controls described in the company's response for the manufacture, processing, packaging or storage of drugs do not comply with CGMP, they are automatically considered adulterated and non-compliant.

Content

The Warning Letter lists a number of violations:

1. Lack of an adequate and written testing programme to assess stability properties. Only 3 months of data were available, with a shelf life of 2 years. There was therefore a lack of sufficient chemical and microbiological tests and data. This meant that there was no proof of compliance with the defined specifications and quality over the shelf life period.

2. The raw materials used had not been sufficiently tested with regard to identity and conformity, e.g. purity, starch and quality. This also included the error frequently identified in recent months that the batches of glycerine used were not tested for the limit values of diethylene glycol (DEG) and ethylene glycol. The FDA points this out again in its Warning Letter:

"The use of glycerin contaminated with DEG and EG has resulted in various lethal poisoning incidents in humans worldwide. See FDA’s guidance document Testing of Glycerin, Propylene Glycol, Maltitol Solution, Hydrogenated Starch Hydrolysate, Sorbitol Solution, and Other High-Risk Drug Components for Diethylene Glycol and Ethylene Glycol to help you meet the CGMP requirements when manufacturing drugs containing ingredients at high-risk for DEG or EG contamination at https://www.fda.gov/media/167974/download.."

FDA Warning Letter to a Manufacturer of an Athlete Muscle Maintenance Creme

On 9 July, the FDA issued a Warning Letter to a Korean manufacturer registered as a manufacturer of over-the-counter drugs. With the Warning Letter, the FDA is responding to the documents it received from this manufacturer in response to two requests in 2022 and 2024. Since the methods, facilities or controls described in the company's response for the manufacture, processing, packaging or storage of drugs do not comply with CGMP, they are automatically considered adulterated and non-compliant.

Content

The Warning Letter lists a number of violations:

1. Lack of an adequate and written testing programme to assess stability properties. Only 3 months of data were available, with a shelf life of 2 years. There was therefore a lack of sufficient chemical and microbiological tests and data. This meant that there was no proof of compliance with the defined specifications and quality over the shelf life period.

2. The raw materials used had not been sufficiently tested with regard to identity and conformity, e.g. purity, starch and quality. This also included the error frequently identified in recent months that the batches of glycerine used were not tested for the limit values of diethylene glycol (DEG) and ethylene glycol. The FDA points this out again in its Warning Letter:

"The use of glycerin contaminated with DEG and EG has resulted in various lethal poisoning incidents in humans worldwide. See FDA’s guidance document Testing of Glycerin, Propylene Glycol, Maltitol Solution, Hydrogenated Starch Hydrolysate, Sorbitol Solution, and Other High-Risk Drug Components for Diethylene Glycol and Ethylene Glycol to help you meet the CGMP requirements when manufacturing drugs containing ingredients at high-risk for DEG or EG contamination at https://www.fda.gov/media/167974/download.."

Conclusion

Since the company could not demonstrate that adequate testing of the manufactured products and starting materials was performed, e.g., the certificates of analysis you submitted for dermaFIT Athlete Muscle Maintenance Cream did not include adequate assay testing for active ingredient content or microbiological testing.

Accordingly, the FDA recommends that a GMP consultant be consulted and advises that the FDA may withhold approval of new applications or supplements until all violations are fully corrected and compliance with CGMP is confirmed.