Parenteral particles

The production process of drugs administered to the body in a parenteral manner, and the drugs themselves, are subject to high requirements in regards to purity. These parenteral solutions are regularised by the national pharmacopoeias and have to be free of any visible particles (particle > 50µm). The limit values for non-visible particles should be followed through serious efforts in production and quality assurance. Products that do not comply with these limit values may not be put into circulation. Depending on the process, 0.2-3.0% of waste through particles is accrued. The costs for this waste depend on the production process and volume. If the waste exceeds the preset specification, the source of the impurification is sought after. The process itself is outside its specification. The simple identification of particles facilitates the detection and elimination of the source. Costs for waste and the attempts to solve the problem are then reduced.

Simple particle identification Rap-ID Particle Systems has developed a system for the automatic chemical analysis of particles on the basis of RAMAN spectroscopy1. The measuring device identifies all particles of organic and inorganic nature larger than 2µm. Apart from the system and extensive training in particle identification with RAMAN, rap-ID offers a particle identification service. The analysis service of rap-ID is a simple access point for the customer to receive information about the particle composition of liquid samples and to introduce counter-measures quickly and effectively. The execution and experiences of these investigations are described in the following. After delivery, the sample is opened and within a few minutes it is sucked through the membrane filter in a clean bench. The metalised polymere membrane is shown in Fig. 1, which is easy to operate due to the aluminium ring setting. Depending on the viscosity of the solution and on the size of the particles to be examined, the size of the nuclear pore is selected. Pores ranging from 0.2 to 8µm are available. If the particles are larger than the pores, they are held back and secreted on the surface. The contrast between particles and membrane is optimised for particle recognition through automatic image analysis. The membrane itself – as all pure metals – produces no RAMAN signal through which the membrane coated with particles can be analysed using the Liquid Particle Explorer. To guarantee optimum results, a suitable filtration regulation is in the process of being developed. The Liquid Particle Explorer was developed to reliably identify particles according to the high standards of measuring devices in a cGMP-controlled surrounding2. Analog to the method of membrane evaluation described in the United States Pharmacopoeia (USP), microscope images of the entire membrane surface covered with particles are automatically recorded and evaluated [LIT VAL Laboratory GIT]. The position, length and width of the particles are determined exactly to the micrometer. The device carries out RAMAN spectroscopic examinations at the centre of gravity of the particles. The resulting spectra are automatically identified on the basis of the pharmaceutical and customer-specific database. The database was created with RAMAN spectra of material samples. The system can therefore recognise mixtures of materials, such as rubber stoppers or dyed polymers, due to their characteristic spectra. Protocols are created regarding conformance with the database and the spectrum quality. An automatically created report provides the size, identification and spectrum quality as well as the result for each individual particle in the form of hypertext. The result is then summarised in a table.

Protein aggregates For protein solutions, such as blood plasma products, insulin or new bio-pharmaceuticals, an aggregation of the protein product is often sorted out when there is a 100% visual inspection of the drugs. The mechanisms for the formation of protein particles have not yet been clarified. The frequent appearance of visible particles necessitates an explanation to the customer or to the authorities, since specifications for approval of the drugs have been exceeded. Isolating protein aggregates on the APSys membrane with subsequent RAMAN spectroscopy is the only way to identify protein aggregates in the size of micrometers and therefore to distinguish them from foreign particles. Fig. 2 shows the surface of the membrane covered with protein aggregates. The protein particles generally result in a characteristic RAMAN spectrum. Through investigations by Popp et al.3, among others, it was proven that proteins could be distinguished on the basis of RAMAN spectra. This was also supported by RAMAN spectra of several thousand protein aggregates of different protein solutions with the Liquid Particle Explorer. Fig. 3 shows the typical spectrum of a 25µm protein particle of an antibody solution, as well as the spectrum of a protein particle of another protein class, which is 15 µm in size.

Foreign particle sources Identifying foreign particles in parenteral solutions supplies direct information regarding the source4. Different sources in the production process may be considered: personnel and clothing, containers and caps etc. The Liquid Particle Explorer database contains 500 RAMAN spectra of these substances. New material samples from the production process can be added to the database by the user within minutes. A process exceeds the specification if rejects in the visual inspection accumulate. The search for the source of the impurification now begins. Up until now, most production personnel rely on experience. They have known their processes for years and can therefore eliminate the impurification source by trial and error. For example, filter candles are replaced or stoppers are checked in regard to their particle load. This may accomplish your goal. However, such an error search often takes days and some errors cannot be contained in this way and may disappear. Only analysis can provide information on the effect of these measures. External laboratories are rarely consulted due to the delay between test and result, and to the small statistical relevancy of a single spectroscopic examination of a particle. Furthermore, due to the subjectivity of the method, a comparison between individual examinations can not often be made. The examinations with the Liquid Particle Explorer enable a statistically relevant and comparable conclusion about the chemical composition of the particles in a relatively short time period. The main impurification sources can be detected on the basis of the particle spectrum of a product sample. Fig. 4 shows the results of the measurements of a product of two different batches. The main impurification source of batch A is polyvinylidenfluoride (PVDF). In a secondary database, PVDF was identified as part of the membrane of a candle filter. A significant increase of the yield was achieved through the removal of the candle filter, a typical sample of batch B is shown in Fig. 4. Continuous monitoring of particle composition increases product safety. To guarantee permanent protection, additional samples and rejects of this product of current batches were continuously examined. At the start, additional less noticeable impurification sources were detected and minimised. Subsequently, some particles remained in the non-visible area and were assigned to this process. The specification of the product was extended through the historical as well as through the product- and process-specific particle spectrum. Deviations from the historical particle profile were therefore quickly detected. The total particle load count can be constant using a particle counter but the composition of the particles may vary significantly. Identifying a new particle type makes latent impurification sources visible before the damage is done. The reliable analysis of particles was carried out for additional particle-sensitive products with great benefits.

Pulmonary drugs The FDA also recommends the characterisation of foreign particles for the growing number of inhalers. The analysis of the particle composition can prove that no particles that are foreign to the process are present in the corresponding products. Another application field is the analysis of drug delivery systems. For quality assurance purposes, the analysis of the material composition of particles is exact to less than a micrometer and provides exact information about the particles and the production processes. From the layer thickness, parameters such as release time of the active substances are reliably determined. RAMAN examinations provide reliable information about the potency of such samples, after calibration to the active substance.

Troubleshooting Through the results of particle measurements, the main impurification sources can be reliably detected within minutes. The source can now be removed quickly through co-operation between the quality assurance and production departments. The Liquid Particle Explorer can be used directly in production. The time required for transport of the samples and for the results is therefore reduced. The customer-specific secondary database quickly provides information about the materials used in the process. After identification results, for example, of 50 particles > 25µm as blue polypropylene, only the blue screw caps made of this material can be considered. Even if the result points to several sources, such as paper or wipes, the number of possibilities is drastically reduced. Problem removal is generally accelerated and the time taken for the removal is minimised. The system is being used to ideal capacity due to short troubleshooting and standstill times. Under control Through continuous monitoring of the particle composition, latent particle sources can be detected before serious damage can be done. This increases product safety and reduces the number of batches restricted for approval. This is especially useful in the production of drugs made of valuable active substances. In the long term, each particle-sensitive production profits from monitoring the particle identification.

Discussions Measurements of the particle composition provides the drug manufacturer with a good starting point for discussions with the authorities. These additional examinations are not mandatory. But the authorities honour the fact that the manufacturer is seriously interested in an explanation of an occurred specification exceeding and has taken the appropriate initiative. The secure identification of visible product particles, e.g. protein aggregates, can form the foundation for the release of a rejected batch as deviation report. High values can be released directly and therefore reduce costs.

rap-ID Particle Systems GmbH T: +49 (0)30 53 04 1232 oliver.valet@rap-ID.com