UK High Court, in Baxter Healthcare v Abbott Laboratories and Central Glass Company Limited, recently found Abbott’s patent invalid and therefore the declaration of non-infringement sought by Baxter unnecessary. It doing so it heavily criticised Abbott’s defence strategy.


The patent in issue, EP 0967975, related to the prevention of the degradation of an anaesthetic gas (sevoflurane, a fluoroether) used to maintain anaesthesia. Sevoflurane is a long established product that has been available for over 15 years which, on contact with Lewis acids decomposes and is therefore stored and provided in resin lined bottles. However, during the history of the product, there have been very few instances of degradation, and those reported have been from contaminated containers. The inventive concept of the patent was asserted to be the inclusion in the fluoroether composition of a compound that inhibits Lewis acids, referred to as “a Lewis acid inhibitor”. The preferred Lewis acid inhibitor being water. Accordingly, Claim 1 of the patent was for a composition containing sevoflurane and water in an amount from 0.015% up saturation (about 0.144%).

In Baxter’s product for which the declaration of non-infringement was sought, the sevoflurane did not have water combined with it in a quantity within this range. Indeed the sevoflurane was anhydrous, but Abbott argued that the Lewis acid inhibitor was water retained in the resin lining of the bottle.

On a number of occasions during the proceedings Baxter had amended its product and process description in respect of the product for which it sought the declaration of non-infringement. Abbott’s policy throughout the proceedings was to decline to make any positive case of infringement but to point out what it perceived to be deficiencies in the description. It took the position that there was insufficient information provided to the court for it to grant the declaration sought.


Claim 1 of the patent was for a composition containing sevoflurane and water in an amount from 0.015% up saturation (about 0.144%). Baxter’s sevoflurane did not have water combined with it in a quantity within this range.

As claim 1 was clearly not infringed, the judgment revolved around claim 2. Claim 2 only required the step of providing a Lewis acid inhibitor “in an amount sufficient to prevent degradation” but did not specify how this amount is to be calculated. It also required the combining of the inhibitor with the sevoflurane. The judgment discusses what is “preventing degradation” and what is “combining”. The House of Lords judgment Kirin Amgen was cited as the correct approach to patent construction. Although interestingly the judge also noted that in marginal cases, uncertainty of construction could still be alleviated by the structured approach represented by the so called protocol questions set out in Improver Corporation v Remington. Despite this reference however in fact the judge did not apply the protocol questions.

“Preventing degradation” in claim 2 was interpreted to mean not the prevention of all degradation, but sufficient prevention of degradation to make the product useable over its shelf life. If it were not given this construction the claim would be invalid for insufficiency.

However, the product has already been on the market for many years and is already useable over its shelf life without the patent (the few examples if it not being so durable being due to handling errors or contamination). Indeed “for the vast bulk of sevoflurane in commerce, the addition of water to any specified level has absolutely no effect”. Accordingly, the judge concluded that claim 2 must be “read in context as requiring that at least the lowest level of water which the specification says the patentee believes to be effective is present, that is to say 150 ppm”. Otherwise, as the judge concluded, the process claims would be invalid from “overwhelming difficulties of sufficiency of description”.

All the claims were in any event anticipated by prior art which described a distillation process which resulted in “an azeotrope in which there is a water phase and a layer of sevoflurane saturated with water”.

Had the patent been valid it is likely that the judge would have granted the declaration of non-infringement in respect of “all packaged sevoflurane not substantially different from the samples that were provided to Abbott”. The judge’s basis for this conclusion on non-infringement was, primarily, that Baxter’s product was anhydrous and the Lewis acid inhibitor was in the resin lining of the bottle. As such the inhibitor is not “combined” with the sevoflurane.


Perhaps the primary interest of this judgment is the judge’s views on Abbott’s strategy of “obstructive non-admission”. Abbott was provided with sample-filled containers as proposed to be manufactured and sold by Baxter. These samples were directly referred to in Baxter’s product description. The legal burden of demonstrating non-infringement was on Baxter. Mallory v. Black Sivalls [1977] RPC 321 established that, where a description alone is relied on, that description must be completely precise and adequate to enable the court to say that no article corresponding to the description could infringe the patent. However the judge’s view was that the provision of a sample was entirely correct. These should have permitted Abbott to find out whether the Baxter product resisted degradation, rather than merely speculating that it might. He described Abbott’s statement of case on infringement as being “as close to being uninformative as it was possible to get”.

It is also interesting to see the so called protocol questions being expressly referred to in this judgment. The judge noted that they are “guidelines and can be useful”. However despite the lip service paid by Lord Hoffmann in Kirin Amgen to their usefulness, one would be hard pressed to find a recent case where they have actually been applied. Despite his comments the judge did not apply them here and chose instead to approach “the purposive interpretation of the words in their context without the assistance that the guidelines provide”.