From unidentified bodies to undesirable chemicals, contamination requires quick analysis to get to the source and prevent a reoccurrence. Philip Payne, Reading Scientific Services Ltd, describes some of the techniques involved.
Contamination of any pharmaceutical or healthcare product is at best undesirable and at worst highly dangerous. Yet despite the rigorous application of Good Manufacturing Practice (GMP) to the production of pharmaceuticals, cases of contamination continue to occur.
Human error, unidentified impurities, manufacturing failures and, most regrettably, deliberate uses of the incorrect ingredients are just some of the routine causes that contribute to the contamination caseload.
Whenever an incident of contamination is identified there is an urgent need to confirm the original finding. This can be done by using investigative analytical techniques that can not only confirm the type of contamination that has occurred but can also help identify the source. Only then can decisions be made on how to deal with the suspect batch, as well as deciding what preventative actions should be undertaken to avoid a repeat of the problem.
Almost by definition, every contamination incident will be unanticipated, and that means that analytical assistance must be on call 24 hours a day to deal with an issue as and when it arises. That was the essential raison d'etre behind the formation of the Emergency Response Service (ERS) established by Reading Scientific Services Ltd (RSSL Pharma) back in 1987. Some 21 years on, the ERS has investigated an estimated 10,000 product emergencies involving pharma, healthcare, food and drink products, with almost 300 incidents being solved on behalf of pharmaceutical and healthcare product producers during 2007.
Foreign bodies sometimes arise because chemical contamination or chemical imbalance results in the precipitation or separation of visible, large particles. Alternatively, all manner of objects may find their way into the product or packaging at every stage of production, distribution and use, often resulting in a customer complaint.
The first stage of any investigation is close examination of the foreign body by stereo or compound light microscopy. The techniques used are generally non-destructive and are applicable to very small samples. In some cases, microscopy will be sufficient on its own to identify a fragment of metal or a piece of glass, but more detailed investigation might also reveal the source.
A variety of techniques can be used to discover the mode of manufacture, shape, and elemental composition of the item from which the glass fragment arose. These results can be compared with reference samples, either from the factory, or from RSSL's database of several hundred samples. Where there is a customer complaint that glass has been found in a product, this extra level of detail can indicate a likely source of contamination, differentiating between any glass that might be found in the production facility and that which might come from domestic items.
Similar distinctions can be made between metal fragments and plastic fragments, and a host of other foreign bodies, such as insect body parts, human hair, dust and microfibres.
One last class of foreign body that is worth considering is visible and sub-visible particles in injectable and ophthalmic solutions. Whilst they cannot be considered as contaminants as such, they are unwelcome. Testing for visible particles is defined by EP 2.9.20. USP<788> and EP 2.9.19 set out limits on the numbers of sub-visible particles (?10µm and ?25µm) that are acceptable in injectables, whereas USP <789> defines limits for ophthalmic solutions.
However, sub-visible particles can also occur in inhalers and foams, and might affect efficacy or product quality. Validated methods can be developed for quantifying the numbers of particles present in every case.
The invisibility of chemical contaminants, except in cases where there is an associated colour change, makes chemical contamination more insidious than foreign body contamination. Most cases come to light as a result of routine QC testing that yield out of specification (OOS) results.
Whenever there is an OOS result suggesting contamination, it is important to verify this finding by repeating the test. This is to rule out laboratory error as a possible explanation. Assuming that the OOS result is genuine, the emergency investigation must then find out what has gone wrong.
To some extent, this challenge is easier for a pharmaceutical product than for a food product. Compared with food and drinks, a pharmaceutical contains fewer ingredients, and the ingredients are already produced and tested under strict regimes of QC and GMP. In theory, there should be fewer opportunities for contamination to occur, and fewer constituents to interfere with the analytical challenge of isolating and identifying a chemical contaminant.
On the other hand, the consequences of contamination might be far more serious with a pharmaceutical product, so there is no room for complacency.
Only last year, the US Food & Drug Administration was obliged to issue a warning that supplies of glycerin should be tested to ensure that diethylene glycol (DEG) was not present. This warning came after several cases of contamination, over a period of years, which had resulted in human fatalities. Among the most serious of these, in Panama in September 2006, more than 40 people died after taking cough syrup containing DEG.
There have also been well-documented problems with supplies of pharmaceuticals and ingredients from emerging economies, particularly China. Institutional corruption and failure to properly regulate and inspect pharmaceutical production has blighted China's reputation, and in 2007, led to the execution of Zheng Xiaoyu, the former head of the SFDA.
A separate case involving Cao Wenzhuang, the administration's former pharmaceutical registration department director, also resulted in imposition of the death penalty, suspended for two years. More recently, the SFDA revoked the manufacturing licence of a factory belonging to Hualian Pharmaceutical in Shanghai after Hualian had been found guilty of making contaminated medicines (the leukaemia drugs, methotrexate and cytarabine hydrochloride).
That is not to characterise the whole of China as a source of poor products. However, it should act as a reminder that the purity of product and ingredients cannot be taken for granted, and every ingredient supplier must provide evidence of their product quality, regardless of where they are based.
As noted above, a case of chemical contamination will often be invisible to the naked eye, but is usually revealed by routine QC analysis. Hence, the investigation of such incidents should always begin by repeating the QC procedure. This will often involve HPLC or Gas Chromatography (GC) analysis, and in the latter case, it may be possible to identify the contaminant directly using GC-Mass Spectrometry (GC-MS). This is a technique that involves separation of the chemical constituents of the product according to their volatility, and identifies specific compounds according to their molecular weight and the molecular weight of their ion fragments.
There are other chemical techniques that might be used. Nuclear Magnetic Resonance spectrometry (NMR) excels in the identification of metabolites or drug degradation products. It is also used for impurity profiling or determination of the drug's optical purity, and increasingly, has a crucial role to play in the detection and identification of the growing problem of counterfeit drug products.
As with subvisible particles, optical isomers are a particular class of contaminant that can be of critical importance. NMR provides a means for determining the optical purity with detection limits in some cases of less than 0.1%. These kinds of results make NMR a very attractive method for determining if pharmaceutical products meet the requirements set by pharmacopoeias of many countries.
It is always useful to have a full production history of the rogue sample, and a control sample against which it can be compared. This helps the experienced chemist to target their efforts more precisely against the unknown chemical that has revealed itself on the HPLC chromatogram. The chromatogram does, of course, reveal information about the contaminant from the size, shape and position (retention time) of the contaminant peaks.
Where UV detection is used, the UV spectrum can also provide some information on the nature of the contaminant (e.g. whether or not it is a substance related to the active). Sometimes, it is possible to use the retention time and UV data together to produce a "shortlist" of possible identities for the contaminant. The candidate compounds can then be sourced and their HPLC retention times checked against that of the contaminant.
This may actually be more easily said than done, since it is not necessarily the case that the contaminating chemical is commercially available. Indeed, the contaminant may only ever be produced in the specific circumstances that have given rise to its presence in this particular instance.
Production equipment, including the very items installed to protect the product from other problems, often proves to be the source of contamination. For example, plastic monomers or oligomers might leach out of on-line filters into pharmaceutical solutions. Monomers, oligomers or plasticisers can also leach from plastic seals and pipes. It takes very little migration to produce a detectable problem.
Other potential contaminants include chemicals from cleaning solutions, cooling waters, and machinery lubricants. Perhaps of greater concern, on very rare occasions, the contaminant has been shown to be an active from an earlier production run of a different pharma product. Plastic monomers and other chemicals (e.g. inks) may also leach from packaging materials. These are not common, but must be evaluated in order to be ruled out of an investigation. All potential explanations must at least be considered.
While it may not be possible to prevent contamination in every case, an investigation is always necessary. The information acquired by an ERS investigation will usually offer an explanation as to how the incident occurred and how it should be addressed. Such data is vital in helping manufacturers decide what measures should be introduced to prevent a recurrence, and to protect the public in the aftermath of contamination being confirmed.